stas 02/01/05 11:20:01
Added: src/docs/1.0/api Apache.pod config.cfg
src/docs/1.0/faqs cgi_to_mod_perl.pod config.cfg
email-etiquette.pod mjtg-news.txt mod_perl.pod
mod_perl_api.pod mod_perl_cgi.pod mod_perl_cvs.pod
mod_perl_faq.pod mod_perl_method_handlers.pod
mod_perl_traps.pod mod_perl_tuning.pod
perl_myth.pod
src/docs/1.0/win32 config.cfg win32_binaries.pod
win32_compile.pod win32_multithread.pod
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porting mod_perl 1.x documents
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1.1 modperl-docs/src/docs/1.0/api/Apache.pod
Index: Apache.pod
===================================================================
=head1 NAME
Apache - Perl interface to the Apache server API
=head1 SYNOPSIS
use Apache ();
=head1 DESCRIPTION
This module provides a Perl interface the Apache API. It is here
mainly for B<mod_perl>, but may be used for other Apache modules that
wish to embed a Perl interpreter. We suggest that you also consult
the description of the Apache C API at http://www.apache.org/docs/.
=head1 THE REQUEST OBJECT
The request object holds all the information that the server needs to
service a request. Apache B<Perl*Handler>s will be given a reference to the
request object as parameter and may choose to update or use it in various
ways. Most of the methods described below obtain information from or
update the request object.
The perl version of the request object will be blessed into the B<Apache>
package, it is really a C<request_rec*> in disguise.
=over 4
=item Apache-E<gt>request([$r])
The Apache-E<gt>request method will return a reference to the request object.
B<Perl*Handler>s can obtain a reference to the request object when it
is passed to them via C<@_>. However, scripts that run under
B<Apache::Registry>, for example, need a way to access the request object.
B<Apache::Registry> will make a request object available to these scripts
by passing an object reference to C<Apache-E<gt>request($r)>.
If handlers use modules such as B<CGI::Apache> that need to access
C<Apache-E<gt>request>, they too should do this (e.g. B<Apache::Status>).
=item $r-E<gt>as_string
Returns a string representation of the request object. Mainly useful
for debugging.
=item $r-E<gt>main
If the current request is a sub-request, this method returns a blessed
reference to the main request structure. If the current request is
the main request, then this method returns C<undef>.
=item $r-E<gt>prev
This method returns a blessed reference to the previous (internal) request
structure or C<undef> if there is no previous request.
=item $r-E<gt>next
This method returns a blessed reference to the next (internal) request
structure or C<undef> if there is no next request.
=item $r-E<gt>last
This method returns a blessed reference to the last (internal) request
structure. Handy for logging modules.
=item $r-E<gt>is_main
Returns true if the current request object is for the main request.
(Should give the same result as C<!$r-E<gt>main>, but will be more efficient.)
=item $r-E<gt>is_initial_req
Returns true if the current request is the first internal request,
returns false if the request is a sub-request or internal redirect.
=item $r-E<gt>allowed($bitmask)
Get or set the allowed methods bitmask. This allowed bitmask should be
set whenever a 405 (method not allowed) or 501 (method not implemented)
answer is returned. The bit corresponding to the method number should be
et.
unless ($r->method_number == M_GET) {
$r->allowed($r->allowed | (1<<M_GET) | (1<<M_HEAD) | (1<<M_OPTIONS));
return HTTP_METHOD_NOT_ALLOWED;
}
=back
=head1 SUB REQUESTS
Apache provides a sub-request mechanism to lookup a uri or filename,
performing all access checks, etc., without actually running the
response phase of the given request. Notice, we have dropped the
C<sub_req_> prefix here. The C<request_rec*> returned by the lookup
methods is blessed into the B<Apache::SubRequest> class. This way,
C<destroy_sub_request()> is called automatically during
C<Apache::SubRequest-E<gt>DESTROY> when the object goes out of scope. The
B<Apache::SubRequest> class inherits all the methods from the
B<Apache> class.
=over 4
=item $r-E<gt>lookup_uri($uri)
my $subr = $r->lookup_uri($uri);
my $filename = $subr->filename;
unless(-e $filename) {
warn "can't stat $filename!\n";
}
=item $r-E<gt>lookup_file($filename)
my $subr = $r->lookup_file($filename);
=item $subr-E<gt>run
if($subr->run != OK) {
$subr->log_error("something went wrong!");
}
=back
=head1 CLIENT REQUEST PARAMETERS
In this section we will take a look at various methods that can be used to
retrieve the request parameters sent from the client.
In the following examples, B<$r> is a request object blessed into the
B<Apache> class, obtained by the first parameter passed to a handler
subroutine
or I<Apache-E<gt>request>
=over 4
=item $r-E<gt>method( [$meth] )
The $r-E<gt>method method will return the request method. It will be a
string such as "GET", "HEAD" or "POST".
Passing an argument will set the method, mainly used for internal redirects.
=item $r-E<gt>method_number( [$num] )
The $r-E<gt>method_number method will return the request method number.
The method numbers are defined by the M_GET, M_POST,... constants
available from the B<Apache::Constants> module. Passing an argument
will set the method_number, mainly used for internal redirects and
testing authorization restriction masks.
=item $r-E<gt>bytes_sent
The number of bytes sent to the client, handy for logging, etc.
=item $r-E<gt>the_request
The request line sent by the client, handy for logging, etc.
=item $r-E<gt>proxyreq
Returns true if the request is proxy http.
Mainly used during the filename translation stage of the request,
which may be handled by a C<PerlTransHandler>.
=item $r-E<gt>header_only
Returns true if the client is asking for headers only,
e.g. if the request method was B<HEAD>.
=item $r-E<gt>protocol
The $r-E<gt>protocol method will return a string identifying the protocol
that the client speaks. Typical values will be "HTTP/1.0" or
"HTTP/1.1".
=item $r-E<gt>hostname
Returns the server host name, as set by full URI or Host: header.
=item $r-E<gt>request_time
Returns the time that the request was made. The time is the local unix
time in seconds since the epoch.
=item $r-E<gt>uri( [$uri] )
The $r-E<gt>uri method will return the requested URI minus optional query
string, optionally changing it with the first argument.
=item $r-E<gt>filename( [$filename] )
The $r-E<gt>filename method will return the result of the I<URI --E<gt>
filename> translation, optionally changing it with the first argument
if you happen to be doing the translation.
=item $r-E<gt>path_info( [$path_info] )
The $r-E<gt>path_info method will return what is left in the path after the
I<URI --E<gt> filename> translation, optionally changing it with the first
argument if you happen to be doing the translation.
=item $r-E<gt>args( [$query_string] )
The $r-E<gt>args method will return the contents of the URI I<query
string>. When called in a scalar context, the entire string is
returned. When called in a list context, a list of parsed I<key> =E<gt>
I<value> pairs are returned, i.e. it can be used like this:
$query = $r->args;
%in = $r->args;
$r-E<gt>args can also be used to set the I<query string>. This can be useful
when redirecting a POST request.
=item $r-E<gt>headers_in
The $r-E<gt>headers_in method will return a %hash of client request
headers. This can be used to initialize a perl hash, or one could use
the $r-E<gt>header_in() method (described below) to retrieve a specific
header value directly.
Will return a I<HASH> reference blessed into the I<Apache::Table>
class when called in a scalar context with no "key" argument. This
requires I<Apache::Table>.
=item $r-E<gt>header_in( $header_name, [$value] )
Return the value of a client header. Can be used like this:
$ct = $r->header_in("Content-type");
$r->header_in($key, $val); #set the value of header '$key'
=item $r-E<gt>content
The $r-E<gt>content method will return the entity body read from the
client, but only if the request content type is
C<application/x-www-form-urlencoded>.
When called in a scalar context, the entire string is
returned. When called in a list context, a list of parsed I<key> =E<gt>
I<value> pairs are returned. *NOTE*: you can only ask for this once,
as the entire body is read from the client.
=item $r-E<gt>read($buf, $bytes_to_read, [$offset])
This method is used to read data from the client,
looping until it gets all of C<$bytes_to_read> or a timeout happens.
An offset may be specified to place the read data at some other place
than the beginning of the string.
In addition, this method sets a timeout before reading with
C<$r-E<gt>soft_timeout>.
=item $r-E<gt>get_remote_host
Lookup the client's DNS hostname. If the configuration directive
B<HostNameLookups> is set to off, this returns the dotted decimal
representation of the client's IP address instead. Might return
I<undef> if the hostname is not known.
=item $r-E<gt>get_remote_logname
Lookup the remote user's system name. Might return I<undef> if the
remote system is not running an RFC 1413 server or if the configuration
directive B<IdentityCheck> is not turned on.
=back
More information about the client can be obtained from the
B<Apache::Connection> object, as described below.
=over 4
=item $c = $r-E<gt>connection
The $r-E<gt>connection method will return a reference to the request
connection object (blessed into the B<Apache::Connection> package).
This is really a C<conn_rec*> in disguise. The following methods can
be used on the connection object:
=over 4
=item $c-E<gt>remote_host
If the configuration directive B<HostNameLookups> is set to on: then
the first time C<$r-E<gt>get_remote_host> is called the server does a DNS
lookup to get the remote client's host name. The result is cached in
C<$c-E<gt>remote_host> then returned. If the server was unable to resolve
the remote client's host name this will be set to "". Subsequent calls
to C<$r-E<gt>get_remote_host> return this cached value.
If the configuration directive B<HostNameLookups> is set to off: calls
to C<$r-E<gt>get_remote_host> return a string that contains the dotted
decimal representation of the remote client's IP address. However this
string is not cached, and C<$c-E<gt>remote_host> is undefined. So, it's
best to to call C<$r-E<gt>get_remote_host> instead of directly accessing
this variable.
=item $c-E<gt>remote_ip
The dotted decimal representation of the remote client's IP address.
This is set by the server when the connection record is created so
is always defined.
You can also set this value by providing an argument to it. This is
helpful if your server is behind a squid accelerator proxy which adds
a X-Forwarded-For header.
=item $c-E<gt>local_addr
A packed SOCKADDR_IN in the same format as returned by
L<Socket/pack_sockaddr_in>, containing the port and address on the
local host that the remote client is connected to. This is set by
the server when the connection record is created so it is always
defined.
=item $c-E<gt>remote_addr
A packed SOCKADDR_IN in the same format as returned by
L<Socket/pack_sockaddr_in>, containing the port and address on the
remote host that the server is connected to. This is set by the
server when the connection record is created so it is always defined.
Among other things, this can be used, together with C<$c-E<gt>local_addr>, to
perform RFC1413 ident lookups on the remote client even when the
configuration directive B<IdentityCheck> is turned off.
Can be used like:
use Net::Ident qw (lookupFromInAddr);
...
my $remoteuser = lookupFromInAddr ($c->local_addr,
$c->remote_addr, 2);
Note that the lookupFromInAddr interface does not currently exist in
the B<Net::Ident> module, but the author is planning on adding it
soon.
=item $c-E<gt>remote_logname
If the configuration directive B<IdentityCheck> is set to on: then the
first time C<$r-E<gt>get_remote_logname> is called the server does an RFC
1413 (ident) lookup to get the remote users system name. Generally for
UNI* systems this is their login. The result is cached in
C<$c-E<gt>remote_logname>
then returned. Subsequent calls to C<$r-E<gt>get_remote_host> return the
cached value.
If the configuration directive B<IdentityCheck> is set to off: then
C<$r-E<gt>get_remote_logname> does nothing and C<$c-E<gt>remote_logname> is
always undefined.
=item $c-E<gt>user( [$user] )
If an authentication check was successful, the authentication handler
caches the user name here. Sets the user name to the optional first
argument.
=item $c-E<gt>auth_type
Returns the authentication scheme that successfully authenticate
C<$c-E<gt>user>, if any.
=item $c-E<gt>aborted
Returns true if the client stopped talking to us.
=item $c-E<gt>fileno( [$direction] )
Returns the client file descriptor. If $direction is 0, the input fd
is returned. If $direction is not null or ommitted, the output fd is
returned.
This can be used to detect client disconnect without doing any I/O,
e.g. using IO::Select.
=back
=back
=head1 SERVER CONFIGURATION INFORMATION
The following methods are used to obtain information from server
configuration and access control files.
=over 4
=item $r-E<gt>dir_config( $key )
Returns the value of a per-directory variable specified by the
C<PerlSetVar> directive.
# <Location /foo/bar>
# PerlSetVar Key Value
# </Location>
my $val = $r->dir_config('Key');
Keys are case-insensitive.
Will return a I<HASH> reference blessed into the
I<Apache::Table> class when called in a scalar context with no
"key" argument. See I<Apache::Table>.
=item $r-E<gt>dir_config-E<gt>get( $key )
Returns the value of a per-directory array variable specified by the
C<PerlAddVar> directive.
# <Location /foo/bar>
# PerlAddVar Key Value1
# PerlAddVar Key Value2
# </Location>
my @val = $r->dir_config->get('Key');
Alternatively in your code you can extend the setting with:
$r->dir_config->add(Key => 'Value3');
Keys are case-insensitive.
Will return a I<HASH> reference blessed into the
I<Apache::Table> class when called in a scalar context with no
"key" argument. See I<Apache::Table>.
=item $r-E<gt>requires
Returns an array reference of hash references, containing information
related to the B<require> directive. This is normally used for access
control, see L<Apache::AuthzAge> for an example.
=item $r-E<gt>auth_type
Returns a reference to the current value of the per directory
configuration directive B<AuthType>. Normally this would be set to
C<Basic> to use the basic authentication scheme defined in RFC 1945,
I<Hypertext Transfer Protocol -- HTTP/1.0>. However, you could set to
something else and implement your own authentication scheme.
=item $r-E<gt>auth_name
Returns a reference to the current value of the per directory
configuration directive B<AuthName>. The AuthName directive creates
protection realm within the server document space. To quote RFC 1945
"These realms allow the protected resources on a server to be
partitioned into a set of protection spaces, each with its own
authentication scheme and/or authorization database." The client uses
the root URL of the server to determine which authentication
credentials to send with each HTTP request. These credentials are
tagged with the name of the authentication realm that created them.
Then during the authentication stage the server uses the current
authentication realm, from C<$r-E<gt>auth_name>, to determine which set of
credentials to authenticate.
=item $r-E<gt>document_root ( [$docroot] )
When called with no argument, returns a reference to the current value
of the per server configuration directive B<DocumentRoot>. To quote the
Apache server documentation, "Unless matched by a directive like Alias,
the server appends the path from the requested URL to the document root
to make the path to the document." This same value is passed to CGI
scripts in the C<DOCUMENT_ROOT> environment variable.
You can also set this value by providing an argument to it. The following
example dynamically sets the document root based on the request's
"Host:" header:
sub trans_handler
{
my $r = shift;
my ($user) = ($r->header_in('Host') =~ /^[^\.]+/);
$r->document_root("/home/$user/www");
return DECLINED;
}
PerlTransHandler trans_handler
=item $r-E<gt>allow_options
The C<$r-E<gt>allow_options> method can be used for
checking if it is OK to run a perl script. The B<Apache::Options>
module provides the constants to check against.
if(!($r->allow_options & OPT_EXECCGI)) {
$r->log_reason("Options ExecCGI is off in this directory",
$filename);
}
=item $r-E<gt>get_server_port
Returns the port number on which the server is listening.
=item $s = $r-E<gt>server
Return a reference to the server info object (blessed into the
B<Apache::Server> package). This is really a C<server_rec*> in
disguise. The following methods can be used on the server object:
=item $s = Apache-E<gt>server
Same as above, but only available during server startup for use in
C<E<lt>PerlE<gt>> sections, B<PerlScript> or B<PerlModule>.
=item $s-E<gt>server_admin
Returns the mail address of the person responsible for this server.
=item $s-E<gt>server_hostname
Returns the hostname used by this server.
=item $s-E<gt>port
Returns the port that this servers listens too.
=item $s-E<gt>is_virtual
Returns true if this is a virtual server.
=item $s-E<gt>names
Returns the wild-carded names for ServerAlias servers.
=item $s-E<gt>dir_config( $key )
Alias for Apache::dir_config.
=item $s-E<gt>warn
Alias for Apache::warn.
=item $s-E<gt>log_error
Alias for Apache::log_error.
=item $s-E<gt>uid
Returns the numeric user id under which the server answers requests.
This is the value of the User directive.
=item $s-E<gt>gid
Returns the numeric group id under which the server answers requests.
This is the value of the Group directive.
=item $s-E<gt>loglevel
Get or set the value of the current LogLevel. This method is added by
the Apache::Log module, which needs to be pulled in.
use Apache::Log;
print "LogLevel = ", $s->loglevel;
$s->loglevel(Apache::Log::DEBUG);
If using Perl 5.005+, the following constants are defined (but not
exported):
Apache::Log::EMERG
Apache::Log::ALERT
Apache::Log::CRIT
Apache::Log::ERR
Apache::Log::WARNING
Apache::Log::NOTICE
Apache::Log::INFO
Apache::Log::DEBUG
=item $r-E<gt>get_handlers( $hook )
Returns a reference to a list of handlers enabled for $hook. $hook is
a string representing the phase to handle. The returned list is a list
of references to the handler subroutines.
$list = $r->get_handlers( 'PerlHandler' );
=item $r-E<gt>set_handlers( $hook, [\&handler, ... ] )
Sets the list if handlers to be called for $hook. $hook is a string
representing the phase to handle. The list of handlers is an anonymous
array of code references to the handlers to install for this request
phase. The special list [ \&OK ] can be used to disable a particular
phase.
$r->set_handlers( PerlLogHandler => [ \&myhandler1, \&myhandler2 ] );
$r->set_handlers( PerlAuthenHandler => [ \&OK ] );
=item $r-E<gt>push_handlers( $hook, \&handler )
Pushes a new handler to be called for $hook. $hook is a string
representing the phase to handle. The handler is a reference to a
subroutine to install for this request phase. This handler will be
called before any configured handlers.
$r->push_handlers( PerlHandler => \&footer);
=item $r-E<gt>current_callback
Returns the name of the handler currently being run. This method is most
useful to PerlDispatchHandlers who wish to only take action for certain
phases.
if($r->current_callback eq "PerlLogHandler") {
$r->warn("Logging request");
}
=back
=head1 SETTING UP THE RESPONSE
The following methods are used to set up and return the response back
to the client. This typically involves setting up $r-E<gt>status(), the
various content attributes and optionally some additional
$r-E<gt>header_out() calls before calling $r-E<gt>send_http_header() which
will
actually send the headers to the client. After this a typical
application will call the $r-E<gt>print() method to send the response
content to the client.
=over 4
=item $r-E<gt>send_http_header( [$content_type] )
Send the response line and all headers to the client.
Takes an optional parameter indicating the content-type of the
response, i.e. 'text/html'.
This method will create headers from the $r-E<gt>content_xxx() and
$r-E<gt>no_cache() attributes (described below) and then append the
headers defined by $r-E<gt>header_out (or $r-E<gt>err_header_out if status
indicates an error).
=item $r-E<gt>get_basic_auth_pw
If the current request is protected by Basic authentication,
this method will return 0, otherwise -1.
The second return value will be the decoded password sent by the client.
($ret, $sent_pw) = $r->get_basic_auth_pw;
=item $r-E<gt>note_basic_auth_failure
Prior to requiring Basic authentication from the client, this method
will set the outgoing HTTP headers asking the client to authenticate
for the realm defined by the configuration directive C<AuthName>.
=item $r-E<gt>handler( [$meth] )
Set the handler for a request.
Normally set by the configuration directive C<AddHandler>.
$r->handler( "perl-script" );
=item $r-E<gt>notes( $key, [$value] )
Return the value of a named entry in the Apache C<notes> table, or
optionally set the value of a named entry. This table is used by Apache
modules to pass messages amongst themselves. Generally if you are
writing handlers in mod_perl you can use Perl variables for this.
$r->notes("MY_HANDLER" => OK);
$val = $r->notes("MY_HANDLER");
Will return a I<HASH> reference blessed into the I<Apache::Table>
class when called in a scalar context with no "key" argument. This
requires I<Apache::Table>.
=item $r-E<gt>pnotes( $key, [$value] )
Like $r-E<gt>notes, but takes any scalar as an value.
$r->pnotes("MY_HANDLER" => [qw(one two)]);
my $val = $r->pnotes("MY_HANDLER");
print $val->[0]; # prints "one"
Advantage over just using a Perl variable is that $r-E<gt>pnotes gets
cleaned up after every request.
=item $r-E<gt>subprocess_env( $key, [$value] )
Return the value of a named entry in the Apache C<subprocess_env>
table, or optionally set the value of a named entry. This table is
used by mod_include. By setting some custom variables inside
a perl handler it is possible to combine perl with mod_include nicely.
If you say, e.g. in a PerlHeaderParserHandler
$r->subprocess_env(MyLanguage => "de");
you can then write in your .shtml document:
<!--#if expr="$MyLanguage = en" -->
English
<!--#elif expr="$MyLanguage = de" -->
Deutsch
<!--#else -->
Sorry
<!--#endif -->
Will return a I<HASH> reference blessed into the I<Apache::Table>
class when called in a scalar context with no "key" argument. This
requires I<Apache::Table>.
=item $r-E<gt>content_type( [$newval] )
Get or set the content type being sent to the client. Content types
are strings like "text/plain", "text/html" or "image/gif". This
corresponds to the "Content-Type" header in the HTTP protocol. Example
of usage is:
$previous_type = $r->content_type;
$r->content_type("text/plain");
=item $r-E<gt>content_encoding( [$newval] )
Get or set the content encoding. Content encodings are string like
"gzip" or "compress". This correspond to the "Content-Encoding"
header in the HTTP protocol.
=item $r-E<gt>content_languages( [$array_ref] )
Get or set the content languages. The content language corresponds to the
"Content-Language" HTTP header and is an array reference containing strings
such as "en" or "no".
=item $r-E<gt>status( $integer )
Get or set the reply status for the client request. The
B<Apache::Constants> module provide mnemonic names for the status codes.
=item $r-E<gt>status_line( $string )
Get or set the response status line. The status line is a string like
"200 Document follows" and it will take precedence over the value specified
using the $r-E<gt>status() described above.
=item $r-E<gt>headers_out
The $r-E<gt>headers_out method will return a %hash of server response
headers. This can be used to initialize a perl hash, or one could use
the $r-E<gt>header_out() method (described below) to retrieve or set a
specific
header value directly.
Will return a I<HASH> reference blessed into the I<Apache::Table>
class when called in a scalar context with no "key" argument. This
requires I<Apache::Table>.
=item $r-E<gt>header_out( $header, $value )
Change the value of a response header, or create a new one. You
should not define any "Content-XXX" headers by calling this method,
because these headers use their own specific methods. Example of use:
$r->header_out("WWW-Authenticate" => "Basic");
$val = $r->header_out($key);
=item $r-E<gt>err_headers_out
The $r-E<gt>err_headers_out method will return a %hash of server response
headers. This can be used to initialize a perl hash, or one could use
the $r-E<gt>err_header_out() method (described below) to retrieve or set a
specific
header value directly.
The difference between headers_out and err_headers_out is that the
latter are printed even on error, and persist across internal redirects
(so the headers printed for ErrorDocument handlers will have them).
Will return a I<HASH> reference blessed into the I<Apache::Table>
class when called in a scalar context with no "key" argument. This
requires I<Apache::Table>.
=item $r-E<gt>err_header_out( $header, [$value] )
Change the value of an error response header, or create a new one.
These headers are used if the status indicates an error.
$r->err_header_out("Warning" => "Bad luck");
$val = $r->err_header_out($key);
=item $r-E<gt>no_cache( $boolean )
This is a flag that indicates that the data being returned is volatile
and the client should be told not to cache it. C<$r-E<gt>no_cache(1)>
adds the headers "Pragma: no-cache" and "Cache-control: no-cache" to
the reponse, therefore it must be called before C<$r-E<gt>send_http_header>.
=item $r-E<gt>print( @list )
This method sends data to the client with C<$r-E<gt>write_client>, but first
sets a timeout before sending with C<$r-E<gt>soft_timeout>. This method is
called instead of CORE::print when you use print() in your mod_perl programs.
This method treats scalar references specially. If an item in @list is a
scalar reference, it will be dereferenced before printing. This is a
performance optimization which prevents unneeded copying of large strings,
and it is subtly different from Perl's standard print() behavior.
Example:
$foo = \"bar"; print($foo);
The result is "bar", not the "SCALAR(0xDEADBEEF)" you might have expected. If
you really want the reference to be printed out, force it into a scalar
context by using C<print(scalar($foo))>.
=item $r-E<gt>send_fd( $filehandle )
Send the contents of a file to the client. Can for instance be used
like this:
open(FILE, $r->filename) || return 404;
$r->send_fd(FILE);
close(FILE);
=item $r-E<gt>internal_redirect( $newplace )
Redirect to a location in the server namespace without
telling the client. For instance:
$r->internal_redirect("/home/sweet/home.html");
=item $r-E<gt>internal_redirect_handler( $newplace )
Same as I<internal_redirect>, but the I<handler> from C<$r> is preserved.
=item $r-E<gt>custom_response($code, $uri)
This method provides a hook into the B<ErrorDocument> mechanism,
allowing you to configure a custom response for a given response
code at request-time.
Example:
use Apache::Constants ':common';
sub handler {
my($r) = @_;
if($things_are_ok) {
return OK;
}
#<Location $r->uri>
#ErrorDocument 401 /error.html
#</Location>
$r->custom_response(AUTH_REQUIRED, "/error.html");
#can send a string too
#<Location $r->uri>
#ErrorDocument 401 "sorry, go away"
#</Location>
#$r->custom_response(AUTH_REQUIRED, "sorry, go away");
return AUTH_REQUIRED;
}
=back
=head1 SERVER CORE FUNCTIONS
=over 4
=item $r-E<gt>soft_timeout($message)
=item $r-E<gt>hard_timeout($message)
=item $r-E<gt>kill_timeout
=item $r-E<gt>reset_timeout
(Documentation borrowed from http_main.h)
There are two functions which modules can call to trigger a timeout
(with the per-virtual-server timeout duration); these are hard_timeout
and soft_timeout.
The difference between the two is what happens when the timeout
expires (or earlier than that, if the client connection aborts) ---
a soft_timeout just puts the connection to the client in an
"aborted" state, which will cause http_protocol.c to stop trying to
talk to the client, but otherwise allows the code to continue normally.
hard_timeout(), by contrast, logs the request, and then aborts it
completely --- longjmp()ing out to the accept() loop in http_main.
Any resources tied into the request resource pool will be cleaned up;
everything that is not will leak.
soft_timeout() is recommended as a general rule, because it gives your
code a chance to clean up. However, hard_timeout() may be the most
convenient way of dealing with timeouts waiting for some external
resource other than the client, if you can live with the restrictions.
When a hard timeout is in scope, critical sections can be guarded
with block_alarms() and unblock_alarms() --- these are declared in
alloc.c because they are most often used in conjunction with
routines to allocate something or other, to make sure that the
cleanup does get registered before any alarm is allowed to happen
which might require it to be cleaned up; they * are, however,
implemented in http_main.c.
kill_timeout() will disarm either variety of timeout.
reset_timeout() resets the timeout in progress.
=item $r-E<gt>post_connection($code_ref)
=item $r-E<gt>register_cleanup($code_ref)
Register a cleanup function which is called just before $r-E<gt>pool is
destroyed.
$r->register_cleanup(sub {
my $r = shift;
warn "registered cleanup called for ", $r->uri, "\n";
});
Cleanup functions registered in the parent process (before forking)
will run once when the server is shut down:
#PerlRequire startup.pl
warn "parent pid is $$\n";
Apache->server->register_cleanup(sub { warn "server cleanup in $$\n"});
The I<post_connection> method is simply an alias for I<register_cleanup>,
as this method may be used to run code after the client connection is closed,
which may not be a I<cleanup>.
=back
=head1 CGI SUPPORT
We also provide some methods that make it easier to support the CGI
type of interface.
=over 4
=item $r-E<gt>send_cgi_header()
Take action on certain headers including I<Status:>, I<Location:> and
I<Content-type:> just as mod_cgi does, then calls
$r-E<gt>send_http_header(). Example of use:
$r->send_cgi_header(<<EOT);
Location: /foo/bar
Content-type: text/html
EOT
=back
=head1 ERROR LOGGING
The following methods can be used to log errors.
=over 4
=item $r-E<gt>log_reason($message, $file)
The request failed, why?? Write a message to the server errorlog.
$r->log_reason("Because I felt like it", $r->filename);
=item $r-E<gt>log_error($message)
Uh, oh. Write a message to the server errorlog.
$r->log_error("Some text that goes in the error_log");
=item $r-E<gt>warn($message)
For pre-1.3 versions of apache, this is just an alias for
C<log_error>. With 1.3+ versions of apache, this message will only be
send to the error_log if B<LogLevel> is set to B<warn> or higher.
=back
=head1 UTILITY FUNCTIONS
=over 4
=item Apache::unescape_url($string)
Handy function for unescapes. Use this one for filenames/paths.
Use unescape_url_info for the result of submitted form data.
=item Apache::unescape_url_info($string)
Handy function for unescapes submitted form data.
In opposite to unescape_url it translates the plus sign to space.
=item Apache::perl_hook($hook)
Returns true if the specified callback hook is enabled:
for (qw(Access Authen Authz ChildInit Cleanup Fixup
HeaderParser Init Log Trans Type))
{
print "$_ hook enabled\n" if Apache::perl_hook($_);
}
=back
=head1 GLOBAL VARIABLES
=over 4
=item $Apache::Server::Starting
Set to true when the server is starting.
=item $Apache::Server::ReStarting
Set to true when the server is starting.
=back
=head1 SEE ALSO
perl(1),
Apache::Constants(3),
Apache::Registry(3),
Apache::Debug(3),
Apache::Options(3),
CGI::Apache(3)
Apache C API notes at C<http://www.apache.org/docs/>
=head1 AUTHORS
Perl interface to the Apache C API written by Doug MacEachern
with contributions from Gisle Aas, Andreas Koenig, Eric Bartley,
Rob Hartill, Gerald Richter, Salvador Ortiz and others.
=cut
1.1 modperl-docs/src/docs/1.0/api/config.cfg
Index: config.cfg
===================================================================
use vars qw(@c);
@c = (
id => 'api_v1',
title => "mod_perl 1.0 API",
abstract => 'This is only a partial API, the rest of the API
documentation is in the source distribution',
chapters => [
qw(
Apache.pod
),
],
);
1.1 modperl-docs/src/docs/1.0/faqs/cgi_to_mod_perl.pod
Index: cgi_to_mod_perl.pod
===================================================================
=head1 NAME
cgi_to_mod_perl - First steps needed to use mod_perl as a CGI replacement
=head1 DESCRIPTION
As the README and other mod_perl documents explain, mod_perl as
a CGI replacement is only a small piece of what the package offers.
However, it is the most popular use of mod_perl, this document is here
so you can cut to the chase.
=head1 INSTALLATION
Read the INSTALL document, in most cases, nothing more is required
than:
perl Makefile.PL && make && make install
=head1 CONFIGURATION
For using mod_perl as a CGI replacement, the recommended configuration
is as follows:
Alias /perl/ /real/path/to/perl-scripts/
<Location /perl>
SetHandler perl-script
PerlHandler Apache::Registry
Options +ExecCGI
</Location>
`Location' refers to the uri, not a directory, think of the above as
<Location http://www.yourname.com/perl>
Any files under that location (which live on your filesystem under
/real/path/to/perl-scripts/), will be handled by the Apache::Registry
module, which emulates the CGI environment. The file must exist and
be executable, in addition, 'Options ExecCGI' must be turned on.
If you wish to have mod_perl execute scripts in any location based on
file extension, use a configuration like so:
<Files ~ "\.pl$">
SetHandler perl-script
PerlHandler Apache::Registry
Options ExecCGI
</Files>
Note that `ScriptAlias' does _not_ work for mod_perl.
=head1 PORTING CGI SCRIPTS
=over 4
=item I/O
If you are using Perl 5.004 most CGI scripts can run under mod_perl
untouched. If you're using 5.003, Perl's built-in C<read()> and
C<print()> functions do not work as they do under CGI. If you're
using CGI.pm, use C<$query-E<gt>print> instead of plain 'ol C<print()>.
=item HEADERS
By default, mod_perl does not send any headers by itself, however, you
may wish to change this:
PerlSendHeader On
Now the response line and common headers will be sent as they are by
mod_cgi. And, just as with mod_cgi, PerlSendHeader will not send a
terminating newline, your script must send that itself, e.g.:
print "Content-type: text/html\n\n";
If you're using CGI.pm and 'print $q-E<gt>header' you do
_not_ need C<PerlSendHeader On>.
=item NPH SCRIPTS
To run a CGI `nph' script under mod_perl, simply add to your code:
local $| = 1;
If you normally set B<PerlSendHeader On>, add this to your httpd.conf:
<Files */nph-*>
PerlSendHeader Off
</Files>
=item PROGRAMMING PRACTICE
CGI lets you get away with sloppy programming, mod_perl does not.
Why? CGI scripts have the lifetime of a single HTTP request as a
separate process. When the request is over, the process goes away and
everything is cleaned up for you, e.g. globals variables, open files,
etc. Scripts running under mod_perl have a longer lifetime, over
several request, different scripts may be in the same process. This
means you must clean up after yourself. You've heard:
always 'use strict' and C<-w>!!!
It's more important under mod_perl Perl than anywhere else, while it's
not required, it B<strongly> recommended, it will save you more time
in the long run. And, of course, clean scripts will still run under
CGI!
=item TRAPS
See L<mod_perl_traps>.
=back
=head1 REPORTING PROBLEMS
Read the L<SUPPORT> file.
=head1 SEE ALSO
Apache::PerlRun(3)
1.1 modperl-docs/src/docs/1.0/faqs/config.cfg
Index: config.cfg
===================================================================
use vars qw(@c);
@c = (
id => 'faqs',
title => "mod_perl FAQs",
abstract => 'Miscellaneous mod_perl documentation',
chapters => [
qw(
cgi_to_mod_perl.pod
mod_perl_cgi.pod
mod_perl_cvs.pod
mod_perl_faq.pod
mod_perl.pod
mod_perl_traps.pod
mod_perl_tuning.pod
mod_perl_api.pod
mod_perl_method_handlers.pod
perl_myth.pod
email-etiquette.pod
),
],
);
1.1 modperl-docs/src/docs/1.0/faqs/email-etiquette.pod
Index: email-etiquette.pod
===================================================================
=head1 The mod_perl Mailing List Guidelines
=for html <!--
email-etiquette: This version dated 21 October 2001.
Please make changes to the .pod source and use pod2html to
create the .html file, thanks. [EMAIL PROTECTED]
-->
Ninety percent of the questions asked on the List have already been
asked before, and answers will be found at one of the links below.
Before you post to the mod_perl List, please read the following.
Hopefully it will save you (and everyone else) some time.
Except where noted the language of all documents is English.
=head1 What is mod_perl?
http://perl.apache.org/guide/intro.html#What_is_mod_perl
=head1 What you need to know to be able to use mod_perl
You need to know about Apache, CGI and of course about Perl itself.
This document explains where to find more information about these and
related topics.
If you already have Perl on your machine then it's likely that you
already have all the Perl documentation. Try typing `perldoc perldoc'
and `man perl'.
=head1 How To Get Help With mod_perl Itself
http://perl.apache.org/ is the mod_perl home, it has links for
everything related to mod_perl.
=head2 Documentation which comes with the distribution
Read the documents which came with mod_perl, particularly the ones
named INSTALL, README and SUPPORT. Also read the documents to which
they refer. Read all the relevant documentation about your operating
system, any tools you use such as compilers and databases, and about
the Apache Web server.
You will get a much better response from the mod_perl List if you can
show that you have made the effort of reading the documentation.
=head2 Other documentation
There are dozens of references to many authoritative resources at
http://perl.apache.org/guide/help.html
=head1 How to get on (and off!) the mod_perl mailing list
=head2 To Get On The List
There are two stages to getting on the list. Firstly you have to send
a mail message to: [EMAIL PROTECTED] and wait for receiving
a response from the mail server with instructions to proceed.
Secondly you have to do what it says in the instructions. After you
are subscribed you will receive a messsage with lots of useful
information about the List. Read it. Print it, even. Save a copy of
it. You *can* get another copy of it, but then you'll feel silly.
Traffic on the mod_perl list can be high at times, several hundred
posts per week, so you might want to consider subscribing to the
mod_perl digest list as an alternative to the mod_perl list. To do so,
send an email to [EMAIL PROTECTED] instead.
=head2 To Get Off The List
Instructions on how to unsubscribe are posted in the headers of every
message which you receive from the List. All you have to do is send a
message to: [EMAIL PROTECTED] (or
[EMAIL PROTECTED] if you are on the digest list)
To prevent malicious individuals from unsubscribing other people, the
mailing list software insists that the message requesting that an
email address be unsubscribed comes from that same address. If your
email address has changed you can still unsubscribe, but you will need
to read the help document, which can be recieved by sending an empty
email to: [EMAIL PROTECTED]
=head1 To post to the List
I<Posting> to the list is just sending a message to the address which
you will be given after you subscribe.
Your message will not be accepted unless you have first
L<subscribed|To Get On The List>.
Do not post to [EMAIL PROTECTED], except to subscribe to
the list! Please do not post to the list itself to attempt to
unsubscribe from it.
=head2 Private Mail
Please do not send private mail to list members unless it is
invited. Even if they have answered your question on the list, you
should continue the discussion on the list.
On the other hand, if someone replies to you personally, you shouldn't
forward the reply to the list unless you have received permission from
this person.
=head2 Other Tips
=head3 Read The Documentation
Please read as much of the documentation as you can before posting.
Please also try to see if your question has been asked recently, there
are links to searchable archives of the list on the mod_perl home page
http://perl.apache.org/.
=head3 Give Full Information
Don't forget that the people reading the list have no idea even what
operating system your computer runs unless you tell them. When
reporting problems include at least the information requested in the
document entitled I<SUPPORT> which you will find in the mod_perl
source distribution.
You can find many excellent examples of posts with good supporting
information by looking at the mod_perl mailing list archives. There
are URLs for several archives (with several different search engines)
on the mod_perl home page. Followup posts will show you how easy the
writer made it for the person who replied to deduce the problem and to
suggest a way of solving it, or to find some further item information.
If after reading the I<SUPPORT> document you think that more
information is needed for your particular problem, but you still don't
know what information to give, ask on the list rather than sending
long scripts and configuration files which few people will have the
time to read.
=head3 Error Messages
If you include error messages in your post, make sure that they are
EXACTLY the messages which you saw. Use a text editor to transfer
them directly into your message if you can. Try not to say things
like "the computer said something about not recognizing a command" but
instead to say something like this:
"When logged in as root I typed the command:
httpd -X
at the console and on the console I saw the message
Syntax error on line 393 of /etc/httpd/conf/httpd.conf: Invalid
command 'PerlHandler', perhaps mis-spelled or defined by a module
not included in the server configuration [FAILED]"
=head3 The Subject Line
The I<Subject:> line is B<very> important. Choose an B<informative>
I<Subject> line for the mail header. Busy list members will skip
messages with unclear I<Subject> lines.
=head3 Preserve The Threads
Messages which all have the same I<Subject> line text (possibly
preceded by the word "Re:" which is automatically added by your
mailer) are together known as a "thread". List members and mail
archive use mail unique-ids and/or the Subject line to sort mail. Do
not change the text without a very good reason, because this may break
the thread. Breaking the thread makes it difficult to follow the
discussion and can be very confusing. It may be better to start a new
thread than to continue an old one if you change the theme.
=head3 Post in PLAIN TEXT
Do not post in HTML. Microsoft users in particular should take
careful note of this. Use either the US-ASCII or ISO-8859-1 (Latin-1)
character set, do not use other character sets which may be designed
for those who do not speak English and which may not be displayable on
many terminals. If you ignore this advice then the chances are
greater that your message will not be read.
=head3 Time and Bandwidth
Remember that thousands of people may read your messages. To save
time and to keep badwidth usage to a minimum, please keep posts
reasonably short, but please make it clear precisely what you are
asking. If you can, send a *small* example of a script or
configuration which reproduces your problem. Please do not send long
scripts which cannot easily be understood. Please do not send large
attachments of many kilobytes, if they are needed then put them on the
Web somewhere or say in your message that you can send them separately
if they are requested.
=head3 Tags
It can be helpful if you use a C<[tag]> in square brackets in the
I<Subject:> line, as well as the brief description of your post.
Some suggested tags are:
ADMIN Stuff about running the List.
ADVOCACY Promoting the use of mod_perl, printing T-shirts, stuff like
that. Please don't start another discussion about whether we
should put this on a different list, we've been there before.
ANNOUNCE Announcements of new software tools, packages and updates.
BENCHMARK Apache/mod_perl performance issues.
BUG Report of possible fault in mod_perl or associated software
- it's better if you can send a patch instead!
DBI Stuff generally concerning Apache/mod_perl interaction
with databases.
FYI For information only.
JOB Any post about mod_perl jobs is welcome as long as it is
brief and to the point. Note: Not "JOBS".
MASON Jonathan Swartz' implementation of Perl embedded in
HTML.
NEWS Items of news likely to be interesting to mod_perlers.
OT Off-topic items, please try to keep traffic low.
PATCH Suggested fix for fault in mod_perl or associated
software.
QUESTION Questions about mod_perl which is not covered by one of the
more specific headings.
RareModules Occasional reminders about little-used modules on CPAN.
RFC Requests for comment from the mod_perl community.
SITE Things about running the Apache/mod_perl servers.
SUMMARY After investigation and perhaps fixing a fault, and after an
extended discussion of a specific topic, it is helpful if
someone summarizes the thread. Don't be shy, everyone will
appreciate the effort.
If you can't find a tag which fits your subject, don't worry. If you
have a very specific subject to discuss, feel free to choose your own
tag, for example C<[mod_proxy]> or C<[Perl Sections]> but remember
that the main reasons for the I<Subject> line are to save people time
and to improve the response to your posts. It does not matter whether
you use C<[UPPER CASE]> or C<[lower case]> or even a C<[Mixture Of
Both]> in the tag. Try to keep the tag short. The tag should be the
first thing in the I<Subject> line.
=head3 If You Don't Get a Reply
Sometimes you will not get a reply. Try to be patient, but it is OK
to try again after a few days. Sometimes the replies you get will be
very short. Please do not worry about that. People are very busy,
that's all.
Of course if your post is C<[OT]> for the list then you may not get a
reply, or you may get one telling you to try a different forum.
=head3 If You Don't Understand a Reply
Just say so.
=head3 General Perl and Apache questions
The mod_perl list is NOT for general questions about Apache and the
Perl language. The majority view is tolerant of off-topic posts, but
it is considered impolite to post general Perl and Apache questions on
the mod_perl list. The best you can hope for is a private reply and a
polite reminder that the question is off-topic for this list. If you
catch someone on a bad day, you might not get the best. There are
often bad days in software development departments...
If the Perl and Apache documentation has not answered your question
then you could try looking at http://lists.perl.org/ or one of the
comp.lang.* newsgroups. From time to time there are efforts to start a
dedicated Perl mailing list and these usually result in a message or
two on the mod_perl list, so it might be worth your while to search
the archives.
Please note that there are now separate mailing lists for ASP, EmbPerl
and Mason, but although we keep trying to get a separate list off the
ground for I<Advocacy> it always seems to end up back on the mod_perl
list.
=head1 Replying to posts
=head2 The "Subject:" line
Make sure that you include the exact I<Subject:> from the original
post, unmodified. This makes it much easier for people (and for the
mail software) to deal with the mail. If you must change the subject
line then please append the words "was originally" plus the original
subject line to your new subject line so that folks can see what is
going on.
=head2 Extracts From Other Posts
When replying to a post, please include B<short> excerpts from the
post to which you are replying so that others can follow the
conversation without having to wade through reams of superfluous text.
If you are lazy about this then messages can get very long indeed and
can become a burden to the other people who might be trying to help.
Make sure that there is a clear distinction between the text(s) of the
message(s) to which you are replying and your reply itself.
=head2 Unnecessary Duplication
If you know that the intended recipients are subscribed to the List,
there is no need to send messages both to them and to the list. They
will get more than one copy of the message which is wasteful.
=head2 Private replies
It is helpful to keep most of your replies on the list, so that others
see that help is being given and so they do not waste time on problems
which have already been solved. Where it is appropriate to take a
discussion off the list (for example where it veers off-topic, as
often happens), say so in a message so that everyone is aware of it.
=head2 Flames
The readers of the mod_perl List aren't interested in that kind of
thing. Don't get involved.
=head1 The mod_perl Guide
You absolutely *must* read the mod_perl Guide.
It is a large document, you probably will want to download it and read
it off-line. If you get the source (see below, L<Corrections and
Contributions>) it comes with a build file to turn the .pod (Plain Old
Documentation) source into HTML, .ps (PostScript) and .pdf (Portable
Document Format). You will need at least Perl version 5.005 to build
it. If you browse the Guide on-line you can use one of the search
engines to find things in it. If you build and browse your own local
HTML copy of the Guide, some of the links in it will not work unless
you are connected to the Internet. Some people prefer to work
offline, using tools like `grep' or `mc' to search the .pod source
directly.
=head2 Finding the Guide
The URL of the Guide is:
http://perl.apache.org/guide/
The sources are available from CPAN and other mirrors:
http://www.cpan.org/authors/id/S/ST/STAS/
=head2 Corrections And Contributions
Corrections and additions to the Guide are welcome. The original is
kept in .pod format, and it is converted to other formats by Perl
code. The Guide changes rather frequently (the CVS snapshot is
updated every six hours!) so if you want to make a contribution make
sure that you get the latest version of the Guide source from
http://stason.org/guide-snapshots
and make your changes to the .pod source only. In the first instance,
post your changes to the mod_perl List for comment.
=begin html <br><hr><br><!--
11 Jun 2000 Initial publication for comment
18 Dec 2000 Minor corrections and additions
21 Oct 2001 Minor corrections, converted to .POD format
-->
=end html
email-etiquette: This version dated 17 October 2001.
1.1 modperl-docs/src/docs/1.0/faqs/mjtg-news.txt
Index: mjtg-news.txt
===================================================================
From: [EMAIL PROTECTED] (M.J.T. Guy)
Newsgroups: comp.lang.perl.misc
Subject: Re: Lexical scope and embedded subroutines.
Date: 6 Jan 1998 18:22:39 GMT
Organization: University of Cambridge, England
Lines: 95
Message-ID: <[EMAIL PROTECTED]>
References: <[EMAIL PROTECTED]> <[EMAIL PROTECTED]> <[EMAIL PROTECTED]>
NNTP-Posting-Host: taurus.cus.cam.ac.uk
In article <[EMAIL PROTECTED]>, Aaron Harsh <[EMAIL PROTECTED]> wrote:
>
>Before I read this thread (and perlsub to get the details) I would have
>assumed the original code was fine.
>
>This behavior brings up the following questions:
> o Is Perl's behavior some sort of speed optimization?
No, but see below.
> o Did the Perl gods just decide that scheme-like behavior was less
>important than the pseduo-static variables described in perlsub?
This subject has been kicked about at some length on perl5-porters.
The current behaviour was chosen as the best of a bad job.
In the context of Perl, it's not obvious what "scheme-like behavior"
means. So it isn't an option. See below for details.
> o Does anyone else find Perl's behavior counter-intuitive?
*Everyone* finds it counterintuitive. The fact that it only generates
a warning rather than a hard error is part of the Perl Gods policy
of hurling thunderbolts at those so irreverent as not to use -w.
> o Did programming in scheme destroy my ability to judge a decent language
>feature?
You're still interested in Perl, so it can't have rotted your brain
completely.
> o Have I misremembered how scheme handles these situations?
Probably not.
> o Do Perl programmers really care how much Perl acts like scheme?
Some do.
> o Should I have stopped this message two or three questions ago?
Yes.
The problem to be solved can be stated as
"When a subroutine refers to a variable which is instantiated more than
once (i.e. the variable is declared in a for loop, or in a subroutine),
which instance of that variable should be used?"
The basic problem is that Perl isn't Scheme (or Pascal or any of the
other comparators that have been used).
In almost all lexically scoped languages (i.e. those in the Algol60
tradition), named subroutines are also lexically scoped. So the scope
of the subroutine is necessarily contained in the scope of any external
variable referred to inside the subroutine. So there's an obvious
answer to the "which instance?" problem.
But in Perl, named subroutines are globally scoped. (But in some
future Perl, you'll be able to write
my sub lex { ... }
to get lexical scoping.) So the solution adopted by other languages
can't be used.
The next suggestion most people come up with is "Why not use the most
recently instantiated variable?". This Does The Right Thing in many
cases, but fails when recursion or other complications are involved.
Consider
sub outer {
inner();
outer();
my $trouble;
inner();
sub inner { $trouble };
outer();
inner();
}
Which instance of $trouble is to be used for each call of inner()?
And why?
The consensus was that an incomplete solution was unacceptable, so
the simple rule "Use the first instance" was adopted instead.
And it is more efficient than possible alternative rules. But that's not
why it was done.
Mike Guy
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl.pod
Index: mod_perl.pod
===================================================================
=head1 NAME
mod_perl - Embed a Perl interpreter in the Apache HTTP server
=head1 DESCRIPTION
The Apache/Perl integration project brings together the full power of
the Perl programming language and the Apache HTTP server. This is
achieved by linking the Perl runtime library into the server and
providing an object oriented Perl interface to the server's C language
API.
These pieces are seamlessly glued together by the `mod_perl' server
plugin, making it is possible to write Apache modules entirely in
Perl. In addition, the persistent interpreter embedded in the server
avoids the overhead of starting an external interpreter and the
penalty of Perl start-up (compile) time.
Without question, the most popular Apache/Perl module is
Apache::Registry module. This module emulates the CGI environment,
allowing programmers to write scripts that run under CGI or
mod_perl without change. Existing CGI scripts may require some
changes, simply because a CGI script has a very short lifetime of one
HTTP request, allowing you to get away with "quick and dirty"
scripting. Using mod_perl and Apache::Registry requires you to be
more careful, but it also gives new meaning to the work "quick"!
Apache::Registry maintains a cache of compiled scripts, which happens
the first time a script is accessed by a child server or once again if
the file is updated on disk.
Although it may be all you need, a speedy CGI replacement is only a
small part of this project. Callback hooks are in place for each stage
of a request. Apache-Perl modules may step in during the handler,
header parser, uri translate, authentication, authorization, access,
type check, fixup and logger stages of a request.
=head1 FAQ
The mod_perl FAQ is maintained by Frank Cringle
E<lt>[EMAIL PROTECTED]<gt>: http://perl.apache.org/faq/
=head1 Apache/Perl API
See 'perldoc Apache' for info on how to use the Perl-Apache API.
See the lib/ directory for example modules and L<apache-modlist.html>
for a comprehensive list.
See the eg/ directory for example scripts.
=head1 mod_perl
For using mod_perl as a CGI replacement see the L<cgi_to_mod_perl> document.
You may load modules at server startup via:
PerlModule Apache::SSI SomeOther::Module
Optionally:
PerlRequire perl-scripts/script_to_load_at_startup.pl
A B<PerlRequire> file is commonly used for intialization during server
startup time. A PerlRequire file name can be absolute or relative to
B<ServerRoot> or a path in C<@INC>. A B<PerlRequire>'d file must
return a true value, i.e., the end of this file should have a:
1; #return true value
See eg/startup.pl for an example to start with.
In an httpd.conf E<lt>Location /fooE<gt> or .htaccess you need:
PerlHandler sub_routine_name
This is the name of the subroutine to call to handle each request.
e.g.
in the PerlModule Apache::Registry this is "Apache::Registry::handler".
If PerlHandler is not a defined subroutine, mod_perl assumes it is a
package name which defines a subroutine named "handler".
PerlHandler Apache::Registry
Would load Registry.pm (if it is not already) and call it's subroutine
"handler".
There are several stages of a request where the Apache API allows a
module to step in and do something. The Apache documentation will
tell you all about those stages and what your modules can do.
By default, these hooks are disabled at compile time, see the INSTALL
document for information on enabling these hooks.
The following configuration directives take one argument, which is the name
of the subroutine to call. If the value is not a subroutine name, mod_perl
assumes it is a package name which implements a 'handler' subroutine.
PerlChildInitHandler (requires apache_1.3.0 or higher)
PerlPostReadRequestHandler (requires apache_1.3.0 or higher)
PerlInitHandler
PerlTransHandler
PerlHeaderParserHandler
PerlAccessHandler
PerlAuthenHandler
PerlAuthzHandler
PerlTypeHandler
PerlFixupHandler
PerlHandler
PerlLogHandler
PerlCleanupHandler
PerlChildExitHandler (requires apache_1.3.0 or higher)
Only ChildInit, ChildExit, PostReadRequest and Trans handlers are not
allowed in .htaccess files.
Modules can check if the code is being run in the parent server during
startup by checking the $Apache::Server::Starting variable.
=head1 RESTARTING
=over 4
=item PerlFreshRestart
By default, if a server is restarted
(ala kill -USR1 `cat logs/httpd.pid`), Perl scripts and modules are
not reloaded. To reload B<PerlRequire>'s, B<PerlModule>'s, other
use()'d modules and flush the B<Apache::Registry> cache, enable with
this command:
PerlFreshRestart On
=item PERL_DESTRUCT_LEVEL
With Apache versions 1.3.0 and higher, mod_perl will call the
perl_destruct() Perl API function during the child exit phase.
This will cause proper execution of B<END> blocks found during server
startup along with invoking the B<DESTROY> method on global objects
who are still alive. It is possible that this operation may take a
long time to finish, causing problems during a restart. If your code
does not contain and B<END> blocks or B<DESTROY> methods which need to
be run during child server shutdown, this destruction can be avoided by
setting the I<PERL_DESTRUCT_LEVEL> environment variable to C<-1>.
=back
=head1 ENVIRONMENT
Under CGI the Perl hash C<%ENV> is magical in that it inherits
environment variables from the parent process and will set them should
a process spawn a child. However, with mod_perl we're in the parent
process that would normally setup the common environment variables
before spawning a CGI process. Therefore, mod_perl must feed these
variables to C<%ENV> directly. Normally, this does not happen until
the response stage of a request when C<PerlHandler> is called. If you
wish to set variables that will be available before then, such as for
a C<PerlAuthenHandler>, you may use the C<PerlSetEnv> configuration
directive:
PerlSetEnv SomeKey SomeValue
You may also use the C<PerlPassEnv> directive to pass an already
existing environment variable to Perl's C<%ENV>:
PerlPassEnv SomeKey
=over 4
=item CONFIGURATION
The C<PerlSetVar> and C<PerlAddVar> directives provide a simple
mechanism for passing information from configuration files to Perl
modules or Registry scripts.
The C<PerlSetVar> directive allows you to set a key/value pair.
PerlSetVar SomeKey SomeValue
Perl modules or scripts retrieve configuration values using the
C<$r-E<gt>dir_config> method.
$SomeValue = $r->dir_config('SomeKey');
The C<PerlAddVar> directive allows you to emulate Perl arrays:
PerlAddVar SomeKey FirstValue
PerlAddVar SomeKey SecondValue
... ... ...
PerlAddVar SomeKey Nth-Value
In the Perl modules the values are extracted using the
C<$r-E<gt>dir_config-E<gt>get> method.
@array = $r->dir_config->get('SomeKey');
Alternatively in your code you can extend the setting with:
$r->dir_config->add(SomeKey => 'Bar');
C<PerlSetVar> and C<PerlAddVar> handle keys case-insensitively.
=item GATEWAY_INTERFACE
The standard CGI environment variable B<GATEWAY_INTERFACE> is set to
C<CGI-Perl/1.1> when running under mod_perl.
=item MOD_PERL
The environment variable `MOD_PERL' is set so scripts can say:
if(exists $ENV{MOD_PERL}) {
#we're running under mod_perl
...
}
else {
#we're NOT running under mod_perl
}
=back
=head1 BEGIN blocks
Perl executes C<BEGIN> blocks during the compile time of code as soon
as possible. The same is true under mod_perl. However, since
mod_perl normally only compiles scripts and modules once, in the
parent server or once per-child, C<BEGIN> blocks in that code will
only be run once. As L<perlmod> explains, once a C<BEGIN> has run, it
is immediately undefined. In the mod_perl environment, this means
C<BEGIN> blocks will not be run during each incoming request unless
that request happens to be one that is compiling the code.
Modules and files pulled in via require/use which contain C<BEGIN>
blocks will be executed:
- only once, if pulled in by the parent process
- once per-child process if not pulled in by the parent process
- an additional time, once per-child process if the module is pulled in off
of disk again via Apache::StatINC
- an additional time, in the parent process on each restart if
PerlFreshRestart is On
- unpredictable if you fiddle with C<%INC> yourself
B<Apache::Registry> scripts which contain C<BEGIN> blocks will be
executed:
- only once, if pulled in by the parent process via
B<Apache::RegistryLoader>
- once per-child process if not pulled in by the parent process
- an additional time, once per-child process if the script file has changed
on disk
- an additional time, in the parent process on each restart if pulled in by
the
parent process via B<Apache::RegistryLoader> and PerlFreshRestart is On
=head1 END blocks
As L<perlmod> explains, an C<END> subroutine is executed as late as
possible, that is, when the interpreter is being exited. In the
mod_perl environment, the interpreter does not exit until the server
is shutdown. However, mod_perl does make a special case for
B<Apache::Registry> scripts.
Normally, C<END> blocks are executed by Perl during it's C<perl_run()>
function, which is called once each time the Perl program is executed,
e.g. once per (mod_cgi) CGI scripts. However, mod_perl only calls
C<perl_run()> once, during server startup. Any C<END> blocks
encountered during main server startup, i.e. those pulled in by the
B<PerlRequire> or by any B<PerlModule> are suspended and run at server
shutdown, aka C<child_exit> (requires apache 1.3.0+). Any C<END>
blocks that are encountered during compilation of Apache::Registry
scripts are called after the script done is running, including
subsequent invocations when the script is cached in memory.
All other C<END> blocks encountered during other Perl*Handler callbacks,
e.g. B<PerlChildInitHandler>, will be suspended while the process is
running and called during C<child_exit> when the process is shutting down.
Module authors may be wish to use C<$r-E<gt>register_cleanup> as an
alternative to C<END> blocks if this behavior is not desirable.
=head1 MEMORY CONSUMPTION
Don't be alarmed by the size of your httpd after you've linked with
mod_perl. No matter what, your httpd will be larger than normal to start,
simply because you've linked with perl's runtime.
Here's I'm just running
% /usr/bin/perl -e '1 while 1'
PID USERNAME PRI NICE SIZE RES STATE TIME WCPU CPU COMMAND
10214 dougm 67 0 668K 212K run 0:04 71.55% 21.13% perl
Now with a few random modules:
% /usr/bin/perl -MDBI -MDBD::mSQL -MLWP::UserAgent -MFileHandle -MIO -MPOSIX
-e '1 while 1'
10545 dougm 49 0 3732K 3340K run 0:05 54.59% 21.48% perl
Here's my httpd linked with libperl.a, not having served a single request:
10386 dougm 5 0 1032K 324K sleep 0:00 0.12% 0.11% httpd-a
You can reduce this if you configure perl 5.004+ with -Duseshrplib.
Here's my httpd linked with libperl.sl, not having served a single request:
10393 dougm 5 0 476K 368K sleep 0:00 0.12% 0.10% httpd-s
Now, once the server starts receiving requests, the embedded
interpreter will compile code for each 'require' file it has not seen
yet, each new Apache::Registry subroutine that's compiled, along with
whatever modules it's use'ing or require'ing. Not to mention
AUTOLOADing. (Modules that you 'use' will be compiled when the server
starts unless they are inside an eval block.) httpd will grow just as
big as our /usr/bin/perl would, or a CGI process for that matter, it
all depends on your setup. The L<mod_perl_tuning> document gives
advice on how to best setup your mod_perl server environment.
The mod_perl INSTALL document explains how to build the Apache::
extensions as shared libraries (with 'perl Makefile.PL DYNAMIC=1').
This may save you some memory, however, it doesn't work on a few
systems such as aix and unixware.
However, on most systems, this strategy will only make the httpd
I<look> smaller. When in fact, an httpd with Perl linked static with
take up less real memory and preform faster than shared libraries at
the same time. See the L<mod_perl_tuning> document for details.
=head2 MEMORY TIPS
=over 4
=item Leaks
If you are using a module that leaks or have code of their own that leaks, in
any case using the apache configuration directive 'MaxRequestsPerChild' is
your best bet to keep the size down.
=item Perl Options
Newer Perl versions also have other options to reduce runtime memory
consumption. See Perl's INSTALL file for details on C<-DPACK_MALLOC>
and C<-DTWO_POT_OPTIMIZE>. With these options, my httpd shrinks down
~150K.
=item Server Startup
Use the B<PerlRequire> and B<PerlModule> directives to load commonly
used modules such as CGI.pm, DBI, etc., when the server is started.
On most systems, server children will be able to share this space.
=item Importing Functions
When possible, avoid importing of a module functions into your
namespace. The aliases which are created can take up quite a bit of
space. Try to use method interfaces and fully qualified
Package::function names instead.
Here's a freshly started httpd who's served one request for a script
using the CGI.pm method interface:
TTY PID USERNAME PRI NI SIZE RES STATE TIME %WCPU %CPU COMMAND
p4 5016 dougm 154 20 3808K 2636K sleep 0:01 9.62 4.07 httpd
Here's a freshly started httpd who's served one request for the same
script using the CGI.pm function interface:
TTY PID USERNAME PRI NI SIZE RES STATE TIME %WCPU %CPU COMMAND
p4 5036 dougm 154 20 3900K 2708K sleep 0:01 3.19 2.18 httpd
Now do the math: take that difference, figure in how many other
scripts import the same functions and how many children you have
running. It adds up!
=item Global Variables
It's always a good idea to stay away from global variables when
possible. Some variables must be global so Perl can see them, such as
a module's B<@ISA> or B<$VERSION> variables. In common practice, a
combination of C<use strict> and C<use vars> keeps modules clean and
reduces a bit of noise. However, B<use vars> also creates aliases as
the B<Exporter> does, which eat up more space. When possible, try to
use fully qualified names instead of B<use vars>. Example:
package MyPackage;
use strict;
@MyPackage::ISA = qw(...);
$MyPackage::VERSION = "1.00";
vs.
package MyPackage;
use strict;
use vars qw(@ISA $VERSION);
@ISA = qw(...);
$VERSION = "1.00";
=item Further Reading
In case I forgot to mention, read Vivek Khera's L<mod_perl_tuning>
document for more tips on improving Apache/mod_perl performance.
=back
=head1 SWITCHES
Normally when you run perl from the command line or have the shell
invoke it with `#!', you may choose to pass perl switch arguments
such as C<-w> or C<-T>. Since the command line is only parsed once,
when the server starts, these switches are unavailable to mod_perl
scripts. However, most command line arguments have a perl special
variable equivilant. For example, the C<$^W> variable coresponds
to the C<-w> switch. Consult L<perlvar> for more details. With
mod_perl it is also possible to turn on warnings globaly via the
B<PerlWarn> directive:
PerlWarn On
The switch which enables taint checks does not have a special
variable, so mod_perl provides the B<PerlTaintCheck> directive to turn
on taint checks. In httpd.conf, enable with:
PerlTaintCheck On
Now, any and all code compiled inside httpd will be checked.
The environment variable B<PERL5OPT> can be used to set additional
perl startup flags such as B<-d> and B<-D>. See L<perlrun>.
=head1 PERSISTENT DATABASE CONNECTIONS
Another popular use of mod_perl is to take advantage of it's
persistance to maintain open database connections. The basic idea
goes like so:
#Apache::Registry script
use strict;
use vars qw($dbh);
$dbh ||= SomeDbPackage->connect(...);
Since C<$dbh> is a global variable, it will not go out of scope,
keeping the connection open for the lifetime of a server process,
establishing it during the script's first request for that process.
It's recommended that you use one of the Apache::* database connection
wrappers. Currently for DBI users there is C<Apache::DBI> and for
Sybase users C<Apache::Sybase::DBlib>. These modules hide the
peculiar code example above. In addition, different scripts may share
a connection, minimizing resource consumption. Example:
#httpd.conf has
# PerlModule Apache::DBI
#DBI scripts look exactly as they do under CGI
use strict;
my $dbh = DBI->connect(...);
Although B<$dbh> shown here will go out of scope when the script ends,
the Apache::DBI module's reference to it does not, keep the connection
open.
B<WARNING:> Do not attempt to open a persistent database connection in
the parent process (via PerlRequire or PerlModule). If you do,
children will get a copy of this handle, causing clashes when the
handle is used by two processes at the same time. Each child must
have it's own unique connection handle.
=head1 STACKED HANDLERS
With the mod_perl stacked handlers mechanism, it is possible for more
than one Perl*Handler to be defined and run during each stage of a
request.
Perl*Handler directives can define any number of subroutines,
e.g. (in config files)
PerlTransHandler OneTrans TwoTrans RedTrans BlueTrans
With the method, Apache-E<gt>push_handlers, callbacks can be added to
the stack by scripts at runtime by mod_perl scripts.
Apache-E<gt>push_handlers takes the callback hook name as it's first
argument and a subroutine name or reference as it's second. e.g.:
Apache->push_handlers("PerlLogHandler", \&first_one);
$r->push_handlers("PerlLogHandler", sub {
print STDERR "__ANON__ called\n";
return 0;
});
After each request, this stack is cleared out.
All handlers will be called unless a handler returns a status other than
OK or DECLINED, this needs to be considered more. Post apache-1.2 will
have a DONE return code to signal termiation of a stage, which Rob and
I came up with while back when first discussing the idea of stacked
handlers. 2.0 won't come for quite sometime, so mod_perl will most
likely handle this before then.
example uses:
CGI.pm maintains a global object for it's plain function interface.
Since the object is global, it does not go out of scope, DESTROY is
never called. CGI-E<gt>new can call:
Apache->push_handlers("PerlCleanupHandler", \&CGI::_reset_globals);
This function will be called during the final stage of a request,
refreshing CGI.pm's globals before the next request comes in.
Apache::DCELogin establishes a DCE login context which must exist for
the lifetime of a request, so the DCE::Login object is stored in a
global variable. Without stacked handlers, users must set
PerlCleanupHandler Apache::DCELogin::purge
in the configuration files to destroy the context. This is not
"user-friendly". Now, Apache::DCELogin::handler can call:
Apache->push_handlers("PerlCleanupHandler", \&purge);
Persistent database connection modules such as Apache::DBI could push
a PerlCleanupHandler handler that iterates over %Connected, refreshing
connections or just checking that ones have not gone stale. Remember,
by the time we get to PerlCleanupHandler, the client has what it wants
and has gone away, we can spend as much time as we want here without
slowing down response time to the client.
PerlTransHandlers may decide, based or uri or other condition, whether
or not to handle a request, e.g. Apache::MsqlProxy. Without stacked
handlers, users must configure:
PerlTransHandler Apache::MsqlProxy::translate
PerlHandler Apache::MsqlProxy
PerlHandler is never actually invoked unless translate() sees the
request is a proxy request ($r-E<gt>proxyreq), if it is a proxy request,
translate() set $r-E<gt>handler("perl-script"), only then will PerlHandler
handle the request. Now, users do not have to specify 'PerlHandler
Apache::MsqlProxy', the translate() function can set it with
push_handlers().
Includes, footers, headers, etc., piecing together a document,
imagine (no need for SSI parsing!):
PerlHandler My::Header Some::Body A::Footer
This was my first test:
#My.pm
package My;
sub header {
my $r = shift;
$r->content_type("text/plain");
$r->send_http_header;
$r->print("header text\n");
}
sub body { shift->print("body text\n") }
sub footer { shift->print("footer text\n") }
1;
__END__
#in config
<Location /foo>
SetHandler "perl-script"
PerlHandler My::header My::body My::footer
</Location>
Parsing the output of another PerlHandler? this is a little more
tricky, but consider:
<Location /foo>
SetHandler "perl-script"
PerlHandler OutputParser SomeApp
</Location>
<Location /bar>
SetHandler "perl-script"
PerlHandler OutputParser AnotherApp
</Location>
Now, OutputParser goes first, but it untie's *STDOUT and re-tie's to
it's own package like so:
package OutputParser;
sub handler {
my $r = shift;
untie *STDOUT;
tie *STDOUT => 'OutputParser', $r;
}
sub TIEHANDLE {
my($class, $r) = @_;
bless { r => $r}, $class;
}
sub PRINT {
my $self = shift;
for (@_) {
#do whatever you want to $_
$self->{r}->print($_ . "[insert stuff]");
}
}
1;
__END__
To build in this feature, configure with:
% perl Makefile.PL PERL_STACKED_HANDLERS=1 [PERL_FOO_HOOK=1,etc]
Another method 'Apache-E<gt>can_stack_handlers' will return TRUE if
mod_perl was configured with PERL_STACKED_HANDLERS=1, FALSE
otherwise.
=head1 PERL METHOD HANDLERS
See L<mod_perl_method_handlers>.
=head1 PERL SECTIONS
With E<lt>PerlE<gt>E<lt>/PerlE<gt> sections, it is possible to
configure your server entirely in Perl.
E<lt>PerlE<gt> sections can contain *any* and as much Perl code as you
wish. These sections are compiled into a special package who's symbol
table mod_perl can then walk and grind the names and values of Perl
variables/structures through the Apache core config gears. Most of
the configurations directives can be represented as C<$Scalars> or
C<@Lists>. A C<@List> inside these sections is simply converted into
a single-space delimited string for you inside. Here's an example:
#httpd.conf
<Perl>
@PerlModule = qw(Mail::Send Devel::Peek);
#run the server as whoever starts it
$User = getpwuid($>) || $>;
$Group = getgrgid($)) || $);
$ServerAdmin = $User;
</Perl>
Block sections such as E<lt>LocationE<gt>E<lt>/LocationE<gt> are
represented in a C<%Hash>, e.g.:
$Location{"/~dougm/"} = {
AuthUserFile => '/tmp/htpasswd',
AuthType => 'Basic',
AuthName => 'test',
DirectoryIndex => [qw(index.html index.htm)],
Limit => {
METHODS => 'GET POST',
require => 'user dougm',
},
};
#If a Directive can take say, two *or* three arguments
#you may push strings and the lowest number of arguments
#will be shifted off the @List
#or use array reference to handle any number greater than
#the minimum for that directive
push @Redirect, "/foo", "http://www.foo.com/";;
push @Redirect, "/imdb", "http://www.imdb.com/";;
push @Redirect, [qw(temp "/here" "http://www.there.com";)];
Other section counterparts include C<%VirtualHost>, C<%Directory> and
C<%Files>.
These are somewhat boring examples, but they should give you the basic
idea. You can mix in any Perl code your heart desires.
See eg/httpd.conf.pl and eg/perl_sections.txt for some examples.
A tip for syntax checking outside of httpd:
<Perl>
#!perl
#... code here ...
__END__
</Perl>
Now you may run C<perl -cx httpd.conf>.
It may be the case that E<lt>PerlE<gt> sections are not completed or
an oversight was made in an certain area. If they do not behave as
you expect, please send a report to the modperl mailing list.
To configure this feature build with
'perl Makefile.PL PERL_SECTIONS=1'
=head1 mod_perl and mod_include integration
As of apache 1.2.0, mod_include can handle Perl callbacks.
A `sub' key value may be anything a Perl*Handler can be:
subroutine name, package name (defaults to package::handler),
Class-E<gt>method call or anonymous sub {}
Example:
Child <!--#perl sub="sub {print $$}" --> accessed
<!--#perl sub="sub {print ++$Access::Cnt }" --> times. <br>
<!--#perl sub="Package::handler" arg="one" arg="two" -->
#don't forget to escape double quotes!
Perl is
<!--#perl sub="sub {for (0..10) {print \"very \"}}"-->
fun to use!
The B<Apache::Include> module makes it simple to include
B<Apache::Registry> scripts with the mod_include perl directive.
Example:
<!--#perl sub="Apache::Include" arg="/perl/ssi.pl" -->
You can also use 'virtual include' to include Apache::Registry scripts
of course. However, using #perl will save the overhead of making
Apache go through the motions of creating/destroying a subrequest and
making all the necessary access checks to see that the request would
be allowed outside of a 'virtual include' context.
To enable perl in mod_include parsed files, when building apache the
following must be present in the Configuration file:
EXTRA_CFLAGS=-DUSE_PERL_SSI -I. `perl -MExtUtils::Embed -ccopts`
mod_perl's Makefile.PL script can take care of this for you as well:
perl Makefile.PL PERL_SSI=1
If you're interested in sprinkling Perl code inside your HTML
documents, you'll also want to look at the Apache::Embperl
(http://perl.apache.org/embperl/), Apache::ePerl and Apache::SSI modules.
=head1 DEBUGGING
=over 4
=item MOD_PERL_TRACE
To enable mod_perl debug tracing configure mod_perl with the
PERL_TRACE option:
perl Makefile.PL PERL_TRACE=1
The trace levels can then be enabled via the B<MOD_PERL_TRACE>
environment variable which can contain any combination of:
d - Trace directive handling during configuration read
s - Trace processing of perl sections
h - Trace Perl*Handler callbacks
g - Trace global variable handling, intepreter construction, END blocks, etc.
all - all of the above
=item spinning httpds
To see where an httpd is "spinning", try adding this to your script or a
startup file:
use Carp ();
$SIG{'USR1'} = sub {
Carp::confess("caught SIGUSR1!");
};
Then issue the command line:
kill -USR1 <spinning_httpd_pid>
=back
=head1 PROFILING
It is possible to profile code run under mod_perl with the
B<Devel::DProf> module available on CPAN. However, you must have
apache version 1.3.0 or higher and the C<PerlChildExitHandler>
enabled. When the server is started, B<Devel::DProf> installs an
C<END> block to write the I<tmon.out> file, which will be run when the
server is shutdown. Here's how to start and stop a server with the
profiler enabled:
% setenv PERL5OPT -d:DProf
% httpd -X -d `pwd` &
... make some requests to the server here ...
% kill `cat logs/httpd.pid`
% unsetenv PERL5OPT
% dprofpp
See also: B<Apache::DProf>
=head1 BENCHMARKING
How much faster is mod_perl that CGI? There are many ways to
benchmark the two, see the C<benchmark/> directory for some examples.
See also: B<Apache::Timeit>
=head1 WARNINGS
See L<mod_perl_traps>.
=head1 SUPPORT
See the L<SUPPORT> file.
=head1 Win32
See L<INSTALL.win32> for building from sources.
Info about win32 binary distributions of mod_perl are available
from:
http://perl.apache.org/distributions/
=head1 REVISION
$Id: mod_perl.pod,v 1.1 2002/01/05 19:20:01 stas Exp $
=head1 AUTHOR
Doug MacEachern
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_api.pod
Index: mod_perl_api.pod
===================================================================
=head1 NAME
Mod_perl_api - accessing the Apache API via mod_perl
=head1 DESCRIPTION
This part of the mod_perl FAQ deals with the Apache Application
Programmer's Interface and how to access it from perl via mod_perl.
=head1 Why can't the server find the handler I wrote?
=head2 Did you enable the required hook?
As described in the mod_perl/INSTALL document, the only callback hook
enabled by default is PerlHandler. If you want to intervene at a
different stage of request processing you must enable the relevant
hook. So to add a special authentication handler, for instance, you
would start the installation process with:
perl Makefile.PL PERL_AUTHEN=1
=head2 Is the handler correctly referenced in the configuration?
Apache must be told to load your handler, either as a module with the
C<PerlModule> directive or as a script with C<PerlRequire>. The
handler subroutine will then be available, but you must also specify
which requests it should process. This is done by naming it in one of
the Perl*Handler directives (PerlInitHandler, PerlTransHandler, etc.).
If this directive is put in access.conf outside of any restrictive
context, your handler will be called during the given phase of each
request processed by the server. You can make it more selective by
restricting it to a directory (-hierarchy) in a E<lt>Directory ...E<gt>
section of access.conf or by putting it in a .htaccess file.
Here is an example of the directives needed to call a handler during
Apache's URI to filename translation phase:
PerlRequire /full/path/to/script/Trans.pl
PerlTransHandler Trans::handler
Trans.pl would start with the statement C<Package Trans;> and define a
subroutine called C<handler>.
=head1 Where can I find examples to get me started?
Check out the Apache-Perl-contrib tarfile at
http://perl.apache.org/src/
Here is an example from Vivek Khera. It allows you to filter files
through a perl script based on their location. Rather than having to
invoke a CGI script, the user just references the file with a normal
URL and it is automagically processed by this code...
#! /usr/local/bin/perl
use strict;
# filter a file before returning it to the web client
# tell Apache to use the PerlHandler FileFilter on file which need
# filtering in the htaccess file:
#
# <Files *.baz>
# SetHandler perl-script
# PerlHandler FileFilter
# </Files>
package FileFilter;
use Apache::Constants ':common';
# find out the file name, then write it out with our header attached
sub handler {
my $r = shift;
my $fileName = $r->filename;
open(F,$fileName) or return NOT_FOUND; # file not found
$r->content_type('text/html');
$r->no_cache(1); # don't be caching my dynamic documents!
$r->send_http_header;
$r->print("<HEAD><TITLE>This is my personal
header!</TITLE></HEAD><BODY>");
# Now copy the file to the client. If you do not need to make any
# changes you can copy it verbatim with the single statement
# $r->send_fd(\*F);
# Otherwise, loop over each line...
while(<F>) {
# mangle the contents here if you want
$r->print ($_);
}
close(F);
$r->print("<HR>Document created: ", scalar localtime time);
$r->print("</BODY>");
OK;
}
1;
=head1 How can I check if mod_perl is available during configuration?
Ralf Engelschall writes:
When you compiled one httpd with and the other without mod_perl, then
you can simply use E<lt>IfModule mod_perl.cE<gt>...E<lt>/IfModuleE<gt>
to surround the stuff for the httpd compiled with mod_perl. The other
then ignores these lines. Example:
<IfModule mod_perl.c>
...stuff for httpd w/ mod_perl...
</IfModule>
<IfModule !mod_perl.c>
...stuff for httpd w/o mod_perl...
</IfModule>
=cut
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_cgi.pod
Index: mod_perl_cgi.pod
===================================================================
=head1 NAME
Mod_perl_cgi - running CGI scripts under mod_perl ($Date: 2002/01/05 19:20:01
$)
=head1 DESCRIPTION
This part of the mod_perl FAQ deals with questions surrounding CGI
scripts.
=head1 Why doesn't my CGI script work at all under mod_perl?
What are the symptoms? Here are some possibilities.
=head2 File not found
Have you made the correct entries in Apache's configuration files? You
need to add the C<Alias /perl/ ...> and C<E<lt>Location /perlE<gt>...>
directives to access.conf as described in mod_perl.pod. And of course the
script must be in the directory specified by the Alias directive and it
must be readable and executable by the user that the web server runs as.
=head2 Forbidden
You don't have permission to access /perl/foo on this server.
chmod 755 /path/to/my/mod_perl/scripts
chmod 755 /path/to/my/mod_perl/scripts/foo
=head2 Internal Server Error
The script died with an execution error. There should be an error message
in the server's error.log saying why. Provided you are using CGI.pm, you
can also see what happens by running the script at a shell prompt.
If the error.log claims there are syntax errors in your script,
but
perl -c /path/to/my/mod_perl/scripts/foo
says it is OK, you have probably used __END__ or __DATA__. Sorry.
Mod_perl's Apache::Registry can't deal with that.
=head1 My CGI script behaves strangely under mod_perl. Why?
Remember that a conventional CGI script always starts up a fresh perl
interpreter, whereas a mod_perl script is reused in the same process
context many times. This means that certain categories of variables can
survive from one invocation of the script to the next. You can make that
work to your advantage, but you can also be caught out by it.
When diagnosing a problem that might be caused by variable lifetimes,
always start the web server in single process mode. Apache normally
spawns a number of child processes to handle queries, and they get used in
round-robin fashion, which makes test results unpredictable.
The command
# ./httpd -X
will start a single-process server with its default configuration. You
can specify a different configuration with the -f flag (and thus use a
different port number for testing, for instance).
Now try executing your script from a browser or with a tool such a wget.
Here are some of the effects that you might see.
=head2 The server terminates after processing the first request
Your script is calling the CORE perl C<exit()> function. That is not
a problem in a conventional CGI script, provided that query processing
is complete. But you almost certainly don't want to exit in a
mod_perl script. It kills the server process that handled the
request, meaning that the advantage of using mod_perl to avoid startup
overhead is lost.
The best way to avoid calling C<exit()> is to restructure the script so
that all execution paths return to a common point at the end of the
script. If this seems impractical you can force the same effect by
placing a label after the last executable statement and replacing calls to
C<exit()> with C<goto label;>
See also what mod_perl_traps says about C<Apache::exit()> and the way
that Apache::Registry causes it to terminate the script but not the
httpd child.
There may be exceptional circumstances in which you explicitly want to
terminate the httpd child at the end of the current request. In this
case C<Apache-E<gt>exit(-2)> should be used.
=head2 Variables retain their value from one request to the next
The so-called sticky query effect happens when the CGI query object, or
another request-specific variable, has a lifetime longer than a single
execution of your script and does not get reinitialised each time the
script is invoked.
This does not matter in a conventional CGI script, because the script
starts with a clean slate for each new request. But a mod_perl script
gets compiled into a subroutine by the Apache::Registry handler and then
processes an arbitrary number of requests. To make sure that both you and
the perl interpreter have the same idea about the meaning of your script,
make sure it starts like this:
#!/usr/bin/perl -w
use strict;
It is good for you! It will make perl point out all variables that you
have not explicitly declared. You can then think about whether they need
to be global or if they can be lexical. Try to declare things lexically,
with my(). These variables disappear when the block they are declared in
ends, so they don't occupy memory when they are not in use and they also
do not need a run-time symbol table entry.
Beware, though, of referring to a lexical variable indirectly from within a
subroutine. To quote L<perlsub/"Private Variables via my()">, the
variable "... now becomes unreachable by the outside world, but retains
its value between calls to ..." the subroutine. You will see classic
"sticky query" symptoms if your code looks like this:
#!/usr/bin/perl -w
use strict;
use CGI;
my $q = CGI->new();
doit();
sub doit {
print($q->header(), $q->start_html());
print('Value is ', $q->param('val')) if $q->param;
$q->print('<p>', $q->startform, 'Value? ',
$q->textfield(-name=>'val', -size=>20), ' ',
$q->submit('enter'), $q->endform);
print($q->end_html());
}
Because you remembered to put the -w switch on the first line, the error
log will tell you that "Variable $q will not stay shared" (provided you
are using perl5.004 or higher).
You must either pass the variable to the subroutine as a parameter,
doit($q)
sub doit {
my($q) = @_;
....
or declare this variable to be global,
use vars qw($q);
$q = CGI->new();
The reason why Perl works this way is explained in a news posting by
Mike Guy that is included with this FAQ (mjtg-news.txt).
=for html
<a href="mjtg-news.txt">mjtg-news.txt</a>
=head2 Variables B<still> retain their value from one request to the next
CGI.pm must pull some extra tricks when it is being used via
Apache::Registry. Versions of CGI.pm before 2.35 did not know this,
and Apache::Registry will complain if you try to use an earlier
version.
CGI.pm detects that it is running under Apache::Registry by looking
for an environment variable. This test can fail if C<use CGI> is
evaluated too early, before the environment has been set up. That can
happen if you have C<use CGI> in a script and pull the script in with
a C<PerlRequire> directive in httpd.conf. Replacing C<use CGI> with
C<require CGI> will fix it.
=head2 Do I have to rewrite my legacy code for mod_perl?
If you have CGI code that seems to be fundamentally at odds with
mod_perl's "compile once, run many" environment, you may be find that
it will work if run under the module C<Apache::PerlRun>. See the
documentation of that module, which is included with recent versions
of mod_perl.
=head1 How can my script continue running after sending the response?
If the client submits a form that will take some time to process, you
may want to say "Thanks for submitting the form" and close the
connection, before processing it.
You can achieve this by registering the subroutine that processes the
form as a cleanup handler:
if($ENV{GATEWAY_INTERFACE} =~ /^CGI-Perl/) {
Apache->request->register_cleanup(sub { doProcess($query) });
}
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_cvs.pod
Index: mod_perl_cvs.pod
===================================================================
=head1 NAME
mod_perl_cvs - Access to the mod_perl CVS development tree
=head1 DESCRIPTION
The mod_perl development tree lives on cvs.apache.org. This tree
contains the latest mod_perl bug fixes and developments that have not
made it to CPAN yet. Welcome to the bleeding edge.
=head1 SYNOPSIS
Just as cvs access to the Apache development tree, the mod_perl code
pulled from cvs is not guaranteed to do anything, especially not
compile or work. But, that's exactly why we are using cvs, so
everyone has access the latest version and can help see to it that
mod_perl does compile and work on all platforms, with the various
versions and configurations of Perl and Apache. Patches are always
welcome, simply testing the latest snapshots is just as, if not more
helpful.
It's recommended to subscribe to the I<modperl-cvs@apache.org> list,
which is the place cvs commit logs and diffs are mailed to; at least
if you're going to work on the code.
Here are the several ways to access the cvs tree.
=over 4
=item cvsup
Cvsup has come out of the FreeBSD group. It's a client/server
beast that offers an efficient way to sync collections of files over
the net, and it is very CVS aware, allowing syncronisation of repositories
or checked out files using the cvs deltas to bring the client side
files up to date with minimal data transfer.
For a FreeBSD cvsup client see:
http://www.freebsd.org/cgi/ports.cgi?query=cvsup&stype=all
Others (SunOS, alpha.osf, linux, Solaris2.4, HPAA 10.2, irix)
ftp://ftp.postgresql.org/pub/CVSup/
Here's a config file for the client (cvsup) to sync modperl sources.
*default tag=.
# comment out the above if you want the raw cvs files
*default host=cvs.apache.org
*default prefix=/path/on/this/machine/to/install/
# a subdir for modperl will appear here ^^^
*default base=/path/on/this/machine/where/cvsup/will/keep/status/info
# you'll never need to look in the 'base' dir.
*default release=cvs delete use-rel-suffix compress
modperl
#apache-src
#apache-docs
#uncomment these two for the latest apache src and/or docs if you want them
=item anoncvs
To checkout a fresh copy from anoncvs use
cvs -d ":pserver:[EMAIL PROTECTED]:/home/cvspublic" login
with the password "anoncvs".
cvs -d ":pserver:[EMAIL PROTECTED]:/home/cvspublic" co modperl
For a basic introduction to anoncvs see http://dev.apache.org/anoncvs.txt
=item from-cvs
A snapshot is rolled of the modperl tree every 6 hours and placed
here:
http://cvs.apache.org/snapshots/modperl/
A snapshot of the Apache development tree is also rolled every 6 hours
and placed here:
http://cvs.apache.org/snapshots/
=back
=head1 SEE ALSO
cvs(1)
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_faq.pod
Index: mod_perl_faq.pod
===================================================================
=head1 NAME
Mod_perl_faq - frequently asked questions about mod_perl ($Date: 2002/01/05
19:20:01 $)
=head1 DESCRIPTION
Mod_perl allows an Apache Web Server to directly execute perl code. This
document is designed to answer questions that arise when designing new
applications, and converting existing applications, to run in the mod_perl
environment.
=head1 QUESTIONS & ANSWERS
=head2 What is mod_perl?
The Apache/Perl integration project brings together the full power of the
Perl programming language and the Apache HTTP server. This is achieved by
linking the Perl runtime library into the server and providing an
object-oriented Perl interface to the server's C language API.
Mod_perl is a bundle of software. One part of the bundle is designed to
be compiled and linked together with Apache and Perl. The remainder is
perl code that provides the object-oriented interface to the "perl-enabled"
web server.
The primary advantages of mod_perl are power and speed. You have full
access to the inner-workings of the web server and can intervene at any
stage of request-processing. This allows for customized processing of (to
name just a few of the phases) URI-E<gt>filename translation, authentication,
response generation and logging. There is very little run-time overhead.
In particular, it is not necessary to start a separate process, as is
often done with web-server extensions. The most wide-spread such
extension mechanism, the Common Gateway Interface (CGI), can be replaced
entirely with perl-code that handles the response generation phase of
request processing. Mod_perl includes a general purpose module for this
purpose (Apache::Registry) that can transparently run existing perl CGI
scripts.
=head2 Where can I get mod_perl?
Mod_perl can be found at
http://www.perl.com/CPAN/modules/by-module/Apache/
=head2 What else do I need?
=over 4
=item Perl
http://www.perl.com/CPAN/src/latest.tar.gz
Win32 users note: at the time of writing, ActiveState's Perl cannot be
used with mod_perl, because it is based on an old version of perl
(perl-5.003_07, build 316).
=item Apache
http://www.apache.org/dist/
=back
=head2 How do I install it?
Here is the easiest way to proceed. Let's assume you have the latest
version of perl (5.004) installed. Unpack the Apache and Mod_perl
tarballs next to one another under a common directory: e.g.
% cd /usr/local/src
% zcat apache_1.2.0.tar.gz | tar xf -
% zcat mod_perl-0.98_12.tar.gz | tar xf -
You probably do not need to change anything in the apache configuration
before compiling. Only if you want to enable additional non-standard
modules do you need to edit apache_1.2.0/src/Configuration. There is no
need to set CC, CFLAGS, etc., because mod_perl will override them with the
values that were used to compile your perl.
Now go to the mod_perl directory and follow the instructions in the
INSTALL file there. If "make test" and "make install" are successful, you
will find the new web server in apache_1.2.0/src/httpd. Move it to a
suitable location, make sure it has access to the correct configuration
files, and fire it up.
=head2 What documentation should I read?
The mod_perl documentation in mod_perl.pod. After you have installed
mod_perl you can read it with the command: C<perldoc mod_perl>.
If you are using mod_perl to extend the server functionality, you will
need to read C<perldoc Apache> and the Apache API notes, which can be
found in apache_1.2.0/htdocs/manual/misc/API.html.
Existing (perl-) CGI scripts should run as-is under mod_perl. There are a
number of reasons why they may need to be adjusted, and these are
discussed later in this FAQ. If you are developing a new CGI script it is
probably best to use CGI.pm. It is part of the standard perl distribution
and its documentation can be read with the command: C<perldoc CGI>.
=head2 How do I run CGI scripts under mod_perl?
Refer to L<mod_perl_cgi> for tips on writing and converting CGI
scripts for mod_perl.
=head2 How do I access the Apache API from mod_perl?
Interfacing with Apache is discussed in L<mod_perl_api>.
=head2 How secure are mod_perl scripts?
Because mod_perl runs within an httpd child process, it runs with the
user-id and group-id specified in the httpd.conf file. This user/group
should have the lowest possible privileges. It should only have access
to world readable files. Even so, careless scripts can give away
information. You would not want your /etc/passwd file to be readable over
the net, for instance.
If you turn on tainting checks, perl can help you to avoid the pitfalls of
using data received from the net. Setting the C<-T> switch on the first line
of the script is not sufficient to enable tainting checks under mod_perl.
You have to include the directive C<PerlTaintCheck On> in the httpd.conf
file.
=head2 What if my script needs higher privileges?
You will have to start a new process that runs under a suitable user-id
(or group-id). If all requests handled by the script will need the higher
privileges, you might as well write it as a suid CGI script. Read the
documentation about suEXEC in Apache-1.2.
Alternatively, pre-process the request with mod_perl and fork a suid
helper process to handle the privileged part of the task.
=head2 Why is httpd using so much memory?
Read the section on "Memory Consumption" in the mod_perl.pod.
Make sure that your scripts are not leaking memory. Global variables
stay around indefinitely, lexical variables (declared with my()) are
destroyed when they go out of scope, provided there are no references
to them from outside of that scope.
To get information about the modules that have been loaded and their
symbol-tables, use the Apache::Status module. It is enabled by adding
these lines to a configuration file (e.g. access.conf);
<Location /perl-status>
SetHandler perl-script
PerlHandler Apache::Status
</Location>
Then look at the URL http://www.your.host/perl-status
Joel Wagner reports that calling an undefined subroutine in a module
can cause a tight loop that consumes all memory. Here is a way to
catch such errors. Define an autoload subroutine
sub UNIVERSAL::AUTOLOAD {
my $class = shift;
warn "$class can't `$UNIVERSAL::AUTOLOAD'!\n";
}
It will produce a nice error in error_log, giving the line number of
the call and the name of the undefined subroutine.
=head2 Do I have to restart the server when I change my Perl code?
Apache::Registry checks the timestamp of scripts that it has loaded
and reloads them if they change. This does not happen for other
handlers, unless you program it yourself. One way to do this is in a
PerlInitHandler. If you define
sub MY::init {
delete $INC{"YourModule.pm"};
require YourModule;
}
as an init handler, it will unconditionally reload YourModule at the
start of each request, which may be useful while you are developing a
new module. It can be made more efficient by storing the timestamp of
the file in a global variable and only reloading when necessary.
=head2 So how do I use mod_perl in conjunction with ErrorDocument?
Andreas Koenig writes:
=over 4
=item *
Set up your testing engine:
LWP comes with debugging capabilities that are sometimes better than
your browser, sometimes your browser is the better testing
device. Make sure you can call lwp-request from the command line and
have your browser ready before you start. I find the C<-x> switch
(extended debugging) and the C<-d> switch (do not display content) most
useful.
=item *
Test your server with
lwp-request -xd http://your.server/test/file.not_there
Carefully examine if the status is 404 and if the headers look good.
If you try 'lwp-request -es', the HTML output will not be the one you
are sending, instead lwp-request will send its own cooked HTML text
(as of version libwww-perl-5.09). Check the real text either with the
C<-x> switch or with telnet or your browser.
=item *
Set up your Errordocument configuration in the testing area. I have
this in my .htaccess file:
ErrorDocument 404 /perl/errors/err404-01
The /perl/ directory is configured to
<Location /perl>
SetHandler perl-script
PerlHandler Apache::Registry::handler
Options ExecCGI
</Location>
I have no PerlSendHeader and no PerlNewSendHeader directive in any
configuration file.
=item *
Repeat step 2 (Test your server)
=item *
Write your error handler in mod_perl. You have to be prepared that you
have to tell both apache *and* the browser the right thing. Basically
you have to tell the browser what the error is, but you have to
pretend to apache that everything was OK. If you tell apache the error
condition, it will handle the situation on its own and add some
unwanted stuff to the output that goes to the browser.
The following works fine for me:
my $r = Apache->request;
$r->content_type('text/html; charset=ISO-8859-1');
$r->send_http_header;
$r->status(200);
...send other HTML stuff...
At the time of the send_http_header we have an error condition of type
404--this is what gets sent to the browser. After that I set status to
200 to silence the apache engine.
I was not successful in trying to do the same with CGI.pm, but I
didn't try very hard.
=item *
Repeat step 2 (Test your server)
=item *
The above is tested with mod_perl/0.98 and 0.99
=item *
Open questions I could not find documentation for (except RTFS): what
exactly is PerlSendHeaders and PerlNewSendHeaders. What is the default
setting for those? How do these cooperate with CGI.pm, Apache.pm,
Apache::Registry?
=back
=head2 How can I reference private library modules?
The best place to put library modules is in the site_perl directory
(usually /usr/lib/perl/site_perl), where perl will find them without
further ado. Local policy may prevent this, in which case you have to
tell the perl interpreter where to find them by adding your private
directory to the @INC array.
There are various ways to do this. One way is to add
use lib '/my/perl/lib';
to each script that needs modules from /my/perl/lib.
Alternatively, you can arrange for all the modules that might be
needed to be loaded when the server starts up. Put a PerlRequire
directive into one of the httpd config files that pulls in a small
module containing the relevant C<use>-statements. There is an example
of this in L<mod_perl_tuning>.
=head2 How can I pass arguments to a SSI script?
Following the documentation, I have put the following in the html
file:
<!--#perl sub="Apache::Include" arg="/perl/ssi.pl" -->
I want to send an argument to the ssi.pl script. How?
It won't work with Apache::Include. Instead of a script, define a
subroutine that's pulled in with PerlRequire or PerlModule, like so:
sub My::ssi {
my($r, $one, $two, $three) = @_;
...
}
In the html file:
<!--#perl sub="My::ssi" arg="one" arg="two" arg="three" -->
=head2 Why is image-file loading so slow when testing with httpd -X ?
If you use Netscape while your server is running in single-process
mode, the "KeepAlive" feature gets in the way. Netscape tries to open
multiple connections and keep them open. Because there is only one
server process listening, each connection has to time-out before the
next succeeds. Turn off KeepAlive in httpd.conf to avoid this effect.
=head2 What can cause a subroutine to suddenly become undefined?
If you sometimes see error messages like this:
[Thu Sep 11 11:03:06 1997] Undefined subroutine
&Apache::ROOT::perl::script1::sub_foo called at
/some/path/perl/script2 line 42.
despite the fact that script2 normally works just fine, it looks like
you have a namespace problem in a library file. If sub_foo is located
in a file that is pulled in by 'require' and both script1 and script2
require it, you need to be sure that the file containing sub_foo sets
a package name. Otherwise, sub_foo gets defined in the namespace that
is active the first time it is required, and the next require is a
no-op because that file is already in %INC.
The solution is simple, set up your require'd file something along
these lines:
package SomeName;
sub sub_foo {...}
Now, have scripts call SomeName::sub_foo() instead of sub_foo().
=head2 What could be causing sporadic errors "in cleanup"?
Some people have seen error messages such as this:
[Fri Sep 26 10:50:08 1997] (in cleanup) no dbproc key in hash
at /usr/lib/perl5/site_perl/Apache/Registry.pm line 119.
Doug writes:
"I have yet to figure out why, but there have been a few arbitrary
cases where Perl (in mod_perl) _insists_ on finding and/or calling a
DESTROY method for an object. Defining an empty sub DESTROY has been
the bandaid for these few cases."
If the specific error message gives you a hint about which object is
causing difficulty, put the C<sub DESTROY { }> in the module that
defines that object class.
=head2 How can I test that my script is running under mod_perl?
There are 2 environment variables you can test.
exists $ENV{"MOD_PERL"} # if running under mod_perl
$ENV{"GATEWAY_INTERFACE"} eq "CGI-Perl/1.1"
The MOD_PERL variable gets set immediately when the perl interpreter
starts up, whereas GATEWAY_INTERFACE may not be set yet when BEGIN
blocks are being processed.
=head2 Where can I get help that I did not find in here?
There is a mailing-list dedicated to mod_perl. It is archived at
http://outside.organic.com/mail-archives/modperl/ and at
http://mathforum.org/epigone/modperl (which has a search
engine) and also at
http://www.progressive-comp.com/Lists/?l=apache-modperl&r=1#apache-modperl
(threaded and indexed).
You can subscribe to the list by sending a mail with the line C<subscribe
modperl> to C<[EMAIL PROTECTED]>.
The mod_perl homepage http://perl.apache.org/ has links to other
mod_perl resources.
The pod source of this FAQ is available at
http://www.ping.de/~fdc/mod_perl/mod_perl_faq.tar.gz
=head2 Where do I send suggestions and corrections concerning this FAQ?
mailto:[EMAIL PROTECTED]
1.1
modperl-docs/src/docs/1.0/faqs/mod_perl_method_handlers.pod
Index: mod_perl_method_handlers.pod
===================================================================
=head1 NAME
mod_perl_method_handlers - How to use mod_perl's MethodHandlers
=head1 DESCRIPTION
Described here are a few examples and hints how to use MethodHandlers
with modperl.
This document assumes familiarity with at least L<perltoot> and
"normal" usage of the Perl*Handlers.
It isn't strictly modperl related, more like "what I use objects for
in my modperl environment".
=head1 SYNOPSIS
If a Perl*Handler is prototyped with '$$', this handler will be
invoked as method, being passed a class name or blessed object as its
first argument and the blessed I<request_rec> as the second argument,
e.g.
package My;
@ISA = qw(BaseClass);
sub handler ($$) {
my($class, $r) = @_;
...;
}
package BaseClass;
sub method ($$) {
my($class, $r) = @_;
...;
}
__END__
Configuration:
PerlHandler My
or
PerlHandler My->handler
Since the handler is invoked as a method, it may inherit from other
classes:
PerlHandler My->method
In this case, the 'My' class inherits this method from 'BaseClass'.
To build in this feature, configure with:
% perl Makefile.PL PERL_METHOD_HANDLERS=1 [PERL_FOO_HOOK=1,etc]
=head1 WHY?
The short version: For pretty much the same reasons we're using OO
perl everywhere else. :-) See L<perltoot>.
The slightly longer version would include some about code reusage and
more clean interface between modules.
=head1 SIMPLE EXAMPLE
Let's start with a simple example.
In httpd.conf:
<Location /obj-handler>
SetHandler perl-script
PerlHandler $My::Obj->method
</Location>
In startup.pl or another PerlRequire'd file:
package This::Class;
$My::Obj = bless {};
sub method ($$) {
my($obj, $r) = @_;
$r->send_http_header("text/plain");
print "$obj isa ", ref($obj);
0;
}
which displays:
This::Class=HASH(0x8411edc) isa This::Class
=head1 A LITTLE MORE ADVANCED
That wasn't really useful, so let's try something little more advanced.
I've a little module which creates a graphical 'datebar' for a client.
(See C<http://www.hip.dk/date_bar>). It's reading a lot of small gifs
with numbers and weekdays, and keeping them in memory in GD.pm's native
format, ready to be copied together and served as gifs.
Now I wanted to use it at another site too, but with a different
look. Obviously something to do with a object. Hence I changed the
module to a object, and can now do a
$Client1::Datebar = new Datebar(
-imagepath => '/home/client1/datebar/',
-size => [131,18],
-elements => 'wday mday mon year hour min',
);
$Client2::Datebar = new Datebar
-imagepath => '/home/client2/datebar/',
-size => [90,14],
-elements => 'wday hour min',
);
And then use $Client1::Datebar and $Client2::Datebar as PerlHandlers in my
Apache configuration. Remember to pass them in literal quotes ('') and not
"" which will be interpolated!
I've a webinterface system to our content-database. I've created
objects to handle the administration of articles, banners, images and
other content. It's then very easy (a few lines of code) to enable
certain modules for each client, depending on their needs.
Another area where I use objects with great success in my modperl
configurations is database abstraction. All our clients using the
webinterface to handle f.x. articles will use a simple module to
handle everything related to the database. Each client have
$Client::Article = new WebAjour::Article(-host => 'www.client.com');
in a module what will be run at server startup.
I can then use some simple methods from the $Client::Article object in
my embperl documents, like:
[- $c = $Client::Article->GetCursor(-layout=>'Frontpage') -]
[$ while($c->Fetch) $]
<h2>[+ $c->f('header') +]</h2>
[+ $c->f('textfield') +]
[$ endwhile $]
Very very useful!
=head1 TRAPS
mod_perl expects object handlers to be in the form of a string, which it
will thaw for you. That means that something like
$r->push_handlers(PerlHandler => '$self->perl_handler_method');
This doesn't work as you might expect, since Perl isn't able to see
$self once it goes to PerlHandler.
The best solution to this is to use an anonymous subroutine and pass it $r
yourself, like this:
$r->push_handlers(PerlHandler =>
sub {
my $r = shift;
$self->perl_handler_method($r);
}
);
=head1 AUTHOR
This document is written by Ask Bjoern Hansen E<lt>[EMAIL PROTECTED]<gt> or
E<lt>[EMAIL PROTECTED]<gt>. Corrections and suggestions are most
welcome. In particular would more examples be appreciated, most of my
own code is way too integrated with our system, which isn't suitable
for public release.
Some codesnippets is from Doug MacEachern.
=head1 SEE ALSO
L<mod_perl>, L<Apache>, L<perltoot> (also available at
C<http://www.perl.com/CPAN/doc/FMTEYEWTK/perltoot.html>)
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_traps.pod
Index: mod_perl_traps.pod
===================================================================
=head1 NAME
mod_perl_traps - common/known mod_perl traps
=head1 DESCRIPTION
In the CGI environment, the server starts a single external process
(Perl interpreter) per HTTP request which runs single script in that
process space. When the request is over, the process goes away
everything is cleaned up and a fresh script is started for the next
request. mod_perl brings Perl inside of the HTTP server not only for
speedup of CGI scripts, but also for access to server functionality
that CGI scripts do not and/or cannot have. Now that we're inside the
server, each process will likely handle more than one Perl script and
keep it "compiled" in memory for longer than a single HTTP request.
This new location and longer lifetime of Perl execution brings with it
some common traps. This document is here to tell you what they are
and how to prevent them. The descriptions here are short, please
consult the mod_perl FAQ for more detail. If you trip over something
not documented here, please send a message to the mod_perl list.
=head2 Migrating from CGI
=over 4
=item *
Be sure to have read L<cgi_to_mod_perl>
=item *
Scripts under Apache::Registry are not run in package B<main>, they
are run in a unique namespace based on the requested uri.
=item *
Apache::Registry scripts cannot contain __END__ or __DATA__ tokens
=item *
Output of C<system>, C<exec> and C<open PIPE, "|program"> calls will
not be sent to the browser unless you Perl was configured with sfio.
=item *
Perl's exit() built-in function cannot be used in mod_perl scripts.
The Apache::exit() function should be used instead. Apache::exit()
automatically overrides the built-in exit() for Apache::Registry
and Apache::PerlRun scripts.
=item *
Your script *will not* run from the command line if your script makes
any direct calls to Apache-E<gt>methods. See Apache::FakeRequest.
=back
=head2 Apache::Registry
=over 4
=item undefined subroutine &Apache::Registry::handler
Interaction with certain modules causes the shortcut configuration to
break, if you see this message change your configuration from this:
<Location /perl>
PerlHandler Apache::Registry
...
</Location>
To this:
PerlModule Apache::Registry
<Location /perl>
PerlHandler Apache::Registry::handler
...
</Location>
=back
=head2 Using CGI.pm and CGI::*
=over 4
=item *
CGI.pm users B<must> have version B<2.39> of the package or higher,
earlier versions will not work under mod_perl.
=item *
If you use the C<SendHeaders()> function, be sure to call
$req_obj-E<gt>cgi-E<gt>done when you are done with a request, just as you
would under I<CGI::MiniSrv>.
=back
=head2 Perl Modules and Extensions
=over 4
=item *
Files pulled in via C<use> or C<require> statements are not
automatically reloaded when changed on disk. See the Apache::StatINC
module to add this functionality.
=item Undefined subroutines
A common trap with required files may result in an error message
similar to this in the error_log:
[Thu Sep 11 11:03:06 1997] Undefined subroutine
&Apache::ROOT::perl::test_2epl::some_function called at
/opt/www/apache/perl/test.pl line 79.
As the above items explains, a file pulled in via C<require> will only
happen once per-process (unless %INC is modified). If the file does
not contain a C<package> declaration, the file's subroutines and
variables will be created in the current package. Under CGI, this is
commonly package C<main>. However, B<Apache::Registry> scripts are
compiled into a unique package name (base on the uri). So, if
multiple scripts in the same process try to require the same file,
which does not declare a package, only one script will actually be
able to see the subroutines. The solution is to read L<perlmodlib>,
L<perlmod> and related perl documentation and re-work your required
file into a module which exports functions or defines a method
interface.
Or something more simple, along these lines:
#required_file.pl
package Test;
sub some_function {...}
...
__END__
Now, have your scripts say:
require "required_file.pl";
Test::some_function();
=item "Use of uninitialized value"
Because of eval context, you may see warnings with useless
filename/line, example:
Use of uninitialized value at (eval 80) line 12.
Use of uninitialized value at (eval 80) line 43.
Use of uninitialized value at (eval 80) line 44.
To track down where this eval is really happening, try using a
B<__WARN__> handler to give you a stack trace:
use Carp ();
local $SIG{__WARN__} = \&Carp::cluck;
=item "Callback called exit"
=item "Out of memory!"
If something goes really wrong with your code, Perl may die with an
"Out of memory!" message and or "Callback called exit". A common
cause of this are never-ending loops, deep recursion or calling an
undefined subroutine. Here's one way to catch the problem:
See Perl's INSTALL document for this item:
=item -DPERL_EMERGENCY_SBRK
If PERL_EMERGENCY_SBRK is defined, running out of memory need not be a
fatal error: a memory pool can allocated by assigning to the special
variable $^M. See perlvar(1) for more details.
If you compile with that option and add 'use Apache::Debug level =E<gt> 4;'
to your PerlScript, it will allocate the $^M emergency pool and the
$SIG{__DIE__} handler will call Carp::confess, giving you a stack
trace which should reveal where the problem is.
See the B<Apache::Resource> module for prevention of spinning httpds.
=item *
If you wish to use a module that is normally linked static with your
Perl, it must be listed in static_ext in Perl's Config.pm to be linked
with httpd during the mod_perl build.
=item Can't load '$Config{sitearchexp}/auto/Foo/Foo.so' for module Foo...
When starting httpd some people have reported seeing an error along
the lines of:
[Thu Jul 9 17:33:42 1998] [error] Can't load
'/usr/local/ap/lib/perl5/site_perl/sun4-solaris/auto/DBI/DBI.so' for
module DBI: ld.so.1: src/httpd: fatal: relocation error: file
/usr/local/ap/lib/perl5/site_perl/sun4-solaris/auto/DBI/DBI.so: symbol
Perl_sv_undef: referenced symbol not found at
/usr/local/ap/lib/perl5/sun4-solaris/5.00404/DynaLoader.pm line 166.
Or similar for the IO module or whatever dynamic module mod_perl tries
to pull in first. The solution is to re-configure, re-build and
re-install Perl and dynamic modules with the following flags when
Configure asks for "additional LD flags":
-Xlinker --export-dynamic
or
-Xlinker -E
This problem is only known to be caused by installing gnu ld under Solaris.
Other known causes of this problem:
OS distributions that ship with a (broken) binary Perl installation.
The `perl' program and `libperl.a' library are somehow built with
different binary compatiblity flags.
The solution to these problems is to rebuild Perl and extension
modules from a fresh source tree. Tip for running Perl's Configure
script, use the `C<-des>' flags to accepts defaults and `C<-D>' flag to
override certain attributes:
% ./Configure -des -Dcc=gcc ... && make test && make install
Read Perl's INSTALL doc for more details.
=back
=head2 Clashes with other Apache C modules
=over 4
=item mod_auth_dbm
If you are a user of B<mod_auth_dbm> or B<mod_auth_db>, you may need
to edit Perl's C<Config> module. When Perl is configured it attempts
to find libraries for ndbm, gdbm, db, etc., for the *DBM*_File
modules. By default, these libraries are linked with Perl and
remembered by the B<Config> module. When mod_perl is configured with
apache, the B<ExtUtils::Embed> module returns these libraries to be
linked with httpd so Perl extensions will work under mod_perl.
However, the order in which these libraries are stored in
B<Config.pm>, may confuse C<mod_auth_db*>. If C<mod_auth_db*> does
not work with mod_perl, take a look at this order with the following
command:
% perl -V:libs
If C<-lgdbm> or C<-ldb> is before C<-lndbm>, example:
libs='-lnet -lnsl_s -lgdbm -lndbm -ldb -ldld -lm -lc -lndir -lcrypt';
Edit B<Config.pm> and move C<-lgdbm> and C<-ldb> to the end of the
list. Here's how to find B<Config.pm>:
% perl -MConfig -e 'print "$Config{archlibexp}/Config.pm\n"'
Another solution for building Apache/mod_perl+mod_auth_dbm under Solaris
is to remove the DBM and NDBM "emulation" from libgdbm.a. Seems
Solaris already provides its own DBM and NDBM, and there's no reason
to build GDBM with them (for us anyway).
In our Makefile for GDBM, we changed
OBJS = $(DBM_OF) $(NDBM_OF) $(GDBM_OF)
to
OBJS = $(GDBM_OF)
Rebuild libgdbm, then Apache/mod_perl.
=back
=head1 REGULAR EXPRESSIONS
=head2 COMPILED REGULAR EXPRESSIONS
When using a regular expression that contains an interpolated Perl variable,
if it is known that the variable (or variables) will not vary during the
execution of the program, a standard optimization technique consists of
adding the C<o> modifier to the regexp pattern, to direct the compiler to
build the internal table once, for the entire lifetime of the script, rather
than every time the pattern is executed. Consider:
my $pat = '^foo$'; # likely to be input from an HTML form field
foreach( @list ) {
print if /$pat/o;
}
This is usually a big win in loops over lists, or when using C<grep> or
C<map>.
In long-lived C<mod_perl> scripts, however, this can pose a problem if the
variable changes according to the invocation. The first invocation of a
fresh httpd child will compile the table and perform the search correctly,
however, all subsequent uses by the httpd child will continue to match the
original pattern, regardless of the current contents of the Perl variables
the pattern is dependent on. Your script will appear broken.
There are two solutions to this problem.
The first is to use C<eval q//>, to force the code to be evaluated each
time. Just make sure that the C<eval> block covers the entire loop of
processing, and not just the pattern match itself.
The above code fragment would be rewritten as:
my $pat = '^foo$';
eval q{
foreach( @list ) {
print if /$pat/o;
}
}
Just saying
eval q{ print if /$pat/o; };
is going to be a horribly expensive proposition.
You use this approach if you require more than one pattern match operator in
a given section of code. If the section contains only one operator (be it an
C<m//> or C<s///>), you can rely on the property of the null pattern, that
reuses the last pattern seen. This leads to the second solution, which also
eliminates the use of C<eval>.
The above code fragment becomes:
my $pat = '^foo$';
"something" =~ /$pat/; # dummy match (MUST NOT FAIL!)
foreach( @list ) {
print if //;
}
The only gotcha is that the dummy match that boots the regular expression
engine must absolutely, positively succeed, otherwise the pattern will not
be cached, and the // will match everything. If you can't count on fixed
text to ensure the match succeeds, you have two possibilities.
If you can guaranteee that the pattern variable contains no meta-characters
(things like C<*>, C<+>, C<^>, C<$>...), you can use the dummy match:
"$pat" =~ /\Q$pat\E/; # guaranteed if no meta-characters present
If there is a possibility that the pattern can contain meta-characters, you
should search for the pattern or the unsearchable C<\377> character as
follows:
"\377" =~ /$pat|^[\377]$/; # guarenteed if meta-characters present
=head2 References
The Camel Book, 2nd edition, p. 538 (p. 356 in the 1st edition).
=head1 AUTHORS
Doug MacEachern, with contributions from
Jens Heunemann E<lt>[EMAIL PROTECTED]<gt>,
David Landgren E<lt>[EMAIL PROTECTED]<gt>,
Mark Mills E<lt>[EMAIL PROTECTED]<gt> and
Randal Schwartz E<lt>[EMAIL PROTECTED]<gt>
1.1 modperl-docs/src/docs/1.0/faqs/mod_perl_tuning.pod
Index: mod_perl_tuning.pod
===================================================================
=head1 NAME
mod_perl_tuning - mod_perl performance tuning
=head1 DESCRIPTION
Described here are examples and hints on how to configure a mod_perl
enabled Apache server, concentrating on tips for configuration for
high-speed performance. The primary way to achieve maximal
performance is to reduce the resources consumed by the mod_perl
enabled HTTPD processes.
This document assumes familiarity with Apache configuration directives
some familiarity with the mod_perl configuration directives, and that
you have already built and installed a mod_perl enabled Apache server.
Please also read the mod_perl documentation that comes with mod_perl
for programming tips. Some configurations below use features from
mod_perl version 1.03 which were not present in earlier versions.
These performance tuning hints are collected from my experiences in
setting up and running servers for handling large promotional sites,
such as The Weather Channel's "Blimp Site-ings" game, the MSIE 4.0
"Subscribe to Win" game, and the MSN Million Dollar Madness game.
=head1 BASIC CONFIGURATION
The basic configuration for mod_perl is as follows. In the
F<httpd.conf> file, I add configuration parameters to make the
C<http://www.domain.com/programs> URL be the base location for all
mod_perl programs. Thus, access to
C<http://www.domain.com/programs/printenv> will run the printenv
script, as we'll see below. Also, any *.perl file will be interpreted
as a mod_perl program just as if it were in the programs directory,
and *.rperl will be mod_perl, but I<without> any HTTP headers
automatically sent; you must do this explicitly. If you don't want
these last two, just leave it out of your configuration.
In the configuration files, I use F</var/www> as the C<ServerRoot>
directory, and F</var/www/docs> as the C<DocumentRoot>. You will need
to change it to match your particular setup. The network address below
in the access to perl-status should also be changed to match yours.
Additions to F<httpd.conf>:
# put mod_perl programs here
# startup.perl loads all functions that we want to use within mod_perl
Perlrequire /var/www/perllib/startup.perl
<Directory /var/www/docs/programs>
AllowOverride None
Options ExecCGI
SetHandler perl-script
PerlHandler Apache::Registry
PerlSendHeader On
</Directory>
# like above, but no PerlSendHeaders
<Directory /var/www/docs/rprograms>
AllowOverride None
Options ExecCGI
SetHandler perl-script
PerlHandler Apache::Registry
PerlSendHeader Off
</Directory>
# allow arbitrary *.perl files to be scattered throughout the site.
<Files *.perl>
SetHandler perl-script
PerlHandler Apache::Registry
PerlSendHeader On
Options +ExecCGI
</Files>
# like *.perl, but do not send HTTP headers
<Files *.rperl>
SetHandler perl-script
PerlHandler Apache::Registry
PerlSendHeader Off
Options +ExecCGI
</Files>
<Location /perl-status>
SetHandler perl-script
PerlHandler Apache::Status
order deny,allow
deny from all
allow from 204.117.82.
</Location>
Now, you'll notice that I use a C<PerlRequire> directive to load in the
file F<startup.perl>. In that file, I include all of the C<use>
statements that occur in any of my mod_perl programs (either from the
programs directory, or the *.perl files). Here is an example:
#! /usr/local/bin/perl
use strict;
# load up necessary perl function modules to be able to call from Perl-SSI
# files. These objects are reloaded upon server restart (SIGHUP or SIGUSR1)
# if PerlFreshRestart is "On" in httpd.conf (as of mod_perl 1.03).
# only library-type routines should go in this directory.
use lib "/var/www/perllib";
# make sure we are in a sane environment.
$ENV{GATEWAY_INTERFACE} =~ /^CGI-Perl/ or die "GATEWAY_INTERFACE not Perl!";
use Apache::Registry (); # for things in the "/programs" URL
# pull in things we will use in most requests so it is read and compiled
# exactly once
use CGI (); CGI->compile(':all');
use CGI::Carp ();
use DBI ();
use DBD::mysql ();
1;
What this does is pull in all of the code used by the programs (but
does not C<import> any of the module methods) into the main HTTPD
process, which then creates the child processes with the code already
in place. You can also put any new modules you like into the
F</var/www/perllib> directory and simply C<use> them in your
programs. There is no need to put C<use lib "/var/www/perllib";> in
all of your programs. You do, however, still need to C<use> the
modules in your programs. Perl is smart enough to know it doesn't
need to recompile the code, but it does need to C<import> the module
methods into your program's name space.
If you only have a few modules to load, you can use the PerlModule
directive to pre-load them with the same effect.
The biggest benefit here is that the child process never needs to
recompile the code, so it is faster to start, and the child process
actually shares the same physical copy of the code in memory due to
the way the virtual memory system in modern operating systems works.
You will want to replace the C<use> lines above with modules you
actually need.
=head2 Simple Test Program
Here's a sample script called F<printenv> that you can stick in the
F<programs> directory to test the functionality of the configuration.
#! /usr/local/bin/perl
use strict;
# print the environment in a mod_perl program under Apache::Registry
print "Content-type: text/html\n\n";
print "<HEAD><TITLE>Apache::Registry Environment</TITLE></HEAD>\n";
print "<BODY><PRE>\n";
print map { "$_ = $ENV{$_}\n" } sort keys %ENV;
print "</PRE></BODY>\n";
When you run this, check the value of the GATEWAY_INTERFACE variable
to see that you are indeed running mod_perl.
=head1 REDUCING MEMORY USE
As a side effect of using mod_perl, your HTTPD processes will be
larger than without it. There is just no way around it, as you have
this extra code to support your added functionality.
On a very busy site, the number of HTTPD processes can grow to be
quite large. For example, on one large site, the typical HTTPD was
about 5Mb large. With 30 of these, all of RAM was exhausted, and we
started to go to swap. With 60 of these, swapping turned into
thrashing, and the whole machine slowed to a crawl.
To reduce thrashing, limiting the maximum number of HTTPD processes to
a number that is just larger than what will fit into RAM (in this
case, 45) is necessary. The drawback is that when the server is
serving 45 requests, new requests will queue up and wait; however, if
you let the maximum number of processes grow, the new requests will
start to get served right away, I<but> they will take much longer to
complete.
One way to reduce the amount of real memory taken up by each process
is to pre-load commonly used modules into the primary HTTPD process so
that the code is shared by all processes. This is accomplished by
inserting the C<use Foo ();> lines into the F<startup.perl> file for
any C<use Foo;> statement in any commonly used Registry program. The
idea is that the operating system's VM subsystem will share the data
across the processes.
You can also pre-load Apache::Registry programs using the
C<Apache::RegistryLoader> module so that the code for these programs
is shared by all HTTPD processes as well.
B<NOTE>: When you pre-load modules in the startup script, you may
need to kill and restart HTTPD for changes to take effect. A simple
C<kill -HUP> or C<kill -USR1> will not reload that code unless you
have set the C<PerlFreshRestart> configuration parameter in
F<httpd.conf> to be "On".
=head1 REDUCING THE NUMBER OF LARGE PROCESSES
Unfortunately, simply reducing the size of each HTTPD process is not
enough on a very busy site. You also need to reduce the quantity of
these processes. This reduces memory consumption even more, and
results in fewer processes fighting for the attention of the CPU. If
you can reduce the quantity of processes to fit into RAM, your
response time is increased even more.
The idea of the techniques outlined below is to offload the normal
document delivery (such as static HTML and GIF files) from the
mod_perl HTTPD, and let it only handle the mod_perl requests. This
way, your large mod_perl HTTPD processes are not tied up delivering
simple content when a smaller process could perform the same job more
efficiently.
In the techniques below where there are two HTTPD configurations, the
same httpd executable can be used for both configurations; there is no
need to build HTTPD both with and without mod_perl compiled into it.
With Apache 1.3 this can be done with the DSO configuration -- just
configure one httpd invocation to dynamically load mod_perl and the
other not to do so.
These approaches work best when most of the requests are for static
content rather than mod_perl programs. Log file analysis become a bit
of a challenge when you have multiple servers running on the same
host, since you must log to different files.
=head2 TWO MACHINES
The simplest way is to put all static content on one machine, and all
mod_perl programs on another. The only trick is to make sure all
links are properly coded to refer to the proper host. The static
content will be served up by lots of small HTTPD processes (configured
I<not> to use mod_perl), and the relatively few mod_perl requests
can be handled by the smaller number of large HTTPD processes on the
other machine.
The drawback is that you must maintain two machines, and this can get
expensive. For extremely large projects, this is the best way to go.
=head2 TWO IP ADDRESSES
Similar to above, but one HTTPD runs bound to one IP address, while
the other runs bound to another IP address. The only difference is
that one machine runs both servers. Total memory usage is reduced
because the majority of files are served by the smaller HTTPD
processes, so there are fewer large mod_perl HTTPD processes sitting
around.
This is accomplished using the F<httpd.conf> directive C<BindAddress>
to make each HTTPD respond only to one IP address on this host. One
will have mod_perl enabled, and the other will not.
=head2 TWO PORT NUMBERS
If you cannot get two IP addresses, you can also split the HTTPD
processes as above by putting one on the standard port 80, and the
other on some other port, such as 8042. The only configuration
changes will be the C<Port> and log file directives in the httpd.conf
file (and also one of them does not have any mod_perl directives).
The major flaw with this scheme is that some firewalls will not allow
access to the server running on the alternate port, so some people
will not be able to access all of your pages.
If you use this approach or the one above with dual IP addresses, you
probably do not want to have the *.perl and *.rperl sections from the
sample configuration above, as this would require that your primary
HTTPD server be mod_perl enabled as well.
Thanks to Gerd Knops for this idea.
=head2 USING ProxyPass WITH TWO SERVERS
To overcome the limitation of the alternate port above, you can use
dual Apache HTTPD servers with just slight difference in
configuration. Essentially, you set up two servers just as you would
with the two port on same IP address method above. However, in your
primary HTTPD configuration you add a line like this:
ProxyPass /programs http://localhost:8042/programs
Where your mod_perl enabled HTTPD is running on port 8042, and has
only the directory F<programs> within its DocumentRoot. This assumes
that you have included the mod_proxy module in your server when it was
built.
Now, when you access http://www.domain.com/programs/printenv it will
internally be passed through to your HTTPD running on port 8042 as the
URL http://localhost:8042/programs/printenv and the result relayed
back transparently. To the client, it all seems as if it is just one
server running. This can also be used on the dual-host version to
hide the second server from view if desired.
=begin html
<P>
A complete configuration example of this technique is provided by
two HTTPD configuration files.
<A HREF="httpd.conf.txt">httpd.conf</A> is for the main server for all
regular pages, and <A HREF="httpd%2bperl.conf.txt">httpd+perl.conf</A> is
for the mod_perl programs accessed in the <CODE>/programs</CODE> URL.
</P>
The directory structure assumes that F</var/www/documents> is the
C<DocumentRoot> directory, and the the mod_perl programs are in
F</var/www/programs> and F</var/www/rprograms>. I start them as
follows:
daemon httpd
daemon httpd -f conf/httpd+perl.conf
=end html
Thanks to Bowen Dwelle for this idea.
=head2 SQUID ACCELERATOR
Another approach to reducing the number of large HTTPD processes on
one machine is to use an accelerator such as Squid (which can be found
at http://squid.nlanr.net/Squid/ on the web) between the clients and
your large mod_perl HTTPD processes. The idea here is that squid will
handle the static objects from its cache while the HTTPD processes
will handle mostly just the mod_perl requests once the cache is
primed. This reduces the number of HTTPD processes and thus reduces
the amount of memory used.
To set this up, just install the current version of Squid (at this
writing, this is version 1.1.22) and use the RunAccel script to start
it. You will need to reconfigure your HTTPD to use an alternate port,
such as 8042, rather than its default port 80. To do this, you can
either change the F<httpd.conf> line C<Port> or add a C<Listen>
directive to match the port specified in the F<squid.conf> file.
Your URLs do not need to change. The benefit of using the C<Listen>
directive is that redirected URLs will still use the default port 80
rather than your alternate port, which might reveal your real server
location to the outside world and bypass the accelerator.
In the F<squid.conf> file, you will probably want to add C<programs>
and C<perl> to the C<cache_stoplist> parameter so that these are
always passed through to the HTTPD server under the assumption that
they always produce different results.
This is very similar to the two port, ProxyPass version above, but the
Squid cache may be more flexible to fine tune for dynamic documents
that do not change on every view. The Squid proxy server also seems
to be more stable and robust than the Apache 1.2.4 proxy module.
One drawback to using this accelerator is that the logfiles will
always report access from IP address 127.0.0.1, which is the local
host loopback address. Also, any access permissions or other user
tracking that requires the remote IP address will always see the local
address. The following code uses a feature of recent mod_perl
versions (tested with mod_perl 1.16 and Apache 1.3.3) to trick Apache
into logging the real client address and giving that information to
mod_perl programs for their purposes.
First, in your F<startup.perl> file add the following code:
use Apache::Constants qw(OK);
sub My::SquidRemoteAddr ($) {
my $r = shift;
if (my ($ip) = $r->header_in('X-Forwarded-For') =~ /([^,\s]+)$/) {
$r->connection->remote_ip($ip);
}
return OK;
}
Next, add this to your F<httpd.conf> file:
PerlPostReadRequestHandler My::SquidRemoteAddr
This will cause every request to have its C<remote_ip> address
overridden by the value set in the C<X-Forwarded-For> header added by
Squid. Note that if you have multiple proxies between the client and
the server, you want the IP address of the last machine before your
accelerator. This will be the right-most address in the
X-Forwarded-For header (assuming the other proxies append their
addresses to this same header, like Squid does.)
If you use apache with mod_proxy at your frontend, you can use Ask
Bjørn Hansen's mod_proxy_add_forward module from
ftp://ftp.netcetera.dk/pub/apache/ to make it insert the
C<X-Forwarded-For> header.
=head1 SUMMARY
To gain maximal performance of mod_perl on a busy site, one must
reduce the amount of resources used by the HTTPD to fit within what
the machine has available. The best way to do this is to reduce
memory usage. If your mod_perl requests are fewer than your static
page requests, then splitting the servers into mod_perl and
non-mod_perl versions further allows you to tune the amount of
resources used by each type of request. Using the C<ProxyPass>
directive allows these multiple servers to appear as one to the
users. Using the Squid accelerator also achieves this effect, but
Squid takes care of deciding when to acccess the large server
automatically.
If all of your requests require processing by mod_perl, then the only
thing you can really do is throw a I<lot> of memory on your machine
and try to tweak the perl code to be as small and lean as possible,
and to share the virtual memory pages by pre-loading the code.
=head1 AUTHOR
This document is written by Vivek Khera. If you need to contact me,
just send email to the mod_perl mailing list.
This document is copyright (c) 1997-1998 by Vivek Khera.
If you have contributions for this document, please post them to the
mailing list. Perl POD format is best, but plain text will do, too.
If you need assistance, contact the mod_perl mailing list at
modperl@apache.org first (send 'subscribe' to [EMAIL PROTECTED]
to subscribe). There are lots of people there that can help. Also,
check the web pages http://perl.apache.org/ and http://www.apache.org/
for explanations of the configuration options.
$Revision: 1.1 $
$Date: 2002/01/05 19:20:01 $
1.1 modperl-docs/src/docs/1.0/faqs/perl_myth.pod
Index: perl_myth.pod
===================================================================
=head1 Popular Perl Complaints and Myths
=head2 Abbreviations
=over 4
=item *
M = Misconception or Myth
=item *
R = Response
=back
=head2 Interpreted vs. Compiled
=over 4
=item M:
Each dynamic perl page hit needs to load the Perl interpreter and
compile the script, then run it each time a dynamic web page is hit.
This dramatically decreases performance as well as makes Perl an
unscalable model since so much overhead is required to search each
page.
=item R:
This myth was true years ago before the advent of mod_perl. mod_perl
loads the interpreter once into memory and never needs to load it
again. Each perl program is only compiled once. The compiled version
is then kept into memory and used each time the program is run. In
this way there is no extra overhead when hitting a mod_perl page.
=back
=head3 Interpreted vs. Compiled (More Gory Details)
=over 4
=item R:
Compiled code always has the potential to be faster than interpreted
code. Ultimately, all interpreted code needs to eventually be converted
to native instructions at some point, and this is invariably has to be
done by a compiled application.
That said, an interpreted language CAN be faster than a comprable
native application in certain situations, given certain, common
programming practices. For example, the allocation and de-allocation of
memory can be a relatively expensive process in a tightly scoped
compiled language, wheras interpreted languages typically use garbage
collectors which don't need to do expensive deallocation in a tight
loop, instead waiting until additional memory is absolutely necessary,
or for a less computationally intensive period. Of course, using a
garbage collector in C would eliminate this edge in this situation, but
where using garbage collectors in C is uncommon, Perl and most other
interpreted languages have built-in garbage collectors.
It is also important to point out that few people use the full
potential of their modern CPU with a single application. Modern CPUs are
not only more than fast enough to run interpreted code, many processors
include instruction sets designed to increase the performance of
interpreted code.
=back
=head2 Perl is overly memory intensive making it unscalable
=over 4
=item M:
Each child process needs the Perl interpreter and all code in memory.
Even with mod_perl httpd processes tend to be overly large, slowing
performance, and requiring much more hardware.
=item R:
In mod_perl the interpreter is loaded into the parent process and
shared between the children. Also, when scripts are loaded into the
parent and the parent forks a child httpd process, that child shares
those scripts with the parent. So while the child may take 6MB of
memory, 5MB of that might be shared meaning it only really uses 1MB
per child. Even 5 MB of memory per child is not uncommon for most web
applications on other languages.
Also, most modern operating systems support the concept of shared
libraries. Perl
can be compiled as a shared library, enabling the bulk of the perl
interpreter to be shared between processes. Some executable formats on
some platforms (I believe ELF is one such format) are able to share
entire executable TEXT segments between unrelated processes.
=back
=head3 More Tuning Advice:
=over 4
=item *
B<Vivek Khera's mod_perl performance tuning guide>(
http://perl.apache.org/tuning/ )
=item *
B<Stas Bekman's Performance Guide>(
http://perl.apache.org/guide/performance.html )
=back
=head2 Not enough support, or tools to develop with Perl. (Myth)
=over 4
=item R:
Of all web applications and languages, Perl arguable has the most
support and tools. B<CPAN> is a central repository of Perl modules
which are freely downloadable and usually well supported. There are
literally thousands of modules which make building web apps in Perl
much easier. There are also countless mailing lists of extremely
responsive Perl experts who usually respond to questions within an
hour. There are also a number of Perl development environments to
make building Perl Web applications easier. Just to name a few, there
is C<Apache::ASP>, C<Mason>, C<embPerl>, C<ePerl>, etc...
=back
=head2 If Perl scales so well, how come no large sites use it? (myth)
=over 4
=item R:
Actually, many large sites DO use Perl for the bulk of their web
applications. Here are some, just as an example: B<e-Toys>,
B<CitySearch>, B<Internet Movie Database>( http://imdb.com ), B<Value
Click> ( http://valueclick.com ), B<Paramount Digital Entertainment>,
B<CMP> ( http://cmpnet.com ), B<HotBot Mail>/B<HotBot Homepages>, and
B<DejaNews> to name a few. Even B<Microsoft> has taken interest in
Perl, ( http://www.activestate.com/press/releases/Microsoft.htm ).
=back
=head2 Perl even with mod_perl, is always slower then C.
=over 4
=item R:
The Perl engine is written in C. There is no point arguing that Perl
is faster than C because anything written in Perl could obviously be
re-written in C. The same holds true for arguing that C is faster than
assembly.
There are two issues to consider here. First of all, many times a web
application written in Perl B<CAN be faster> than C thanks to the low
level optimizations in the Perl compiler. In other words, its easier
to write poorly written C then well written Perl. Secondly its
important to weigh all factors when choosing a language to build a web
application in. Time to market is often one of the highest priorities
in creating a web application. Development in Perl can often be twice
as fast as in C. This is mostly due to the differences in the
language themselves as well as the wealth of free examples and modules
which speed development significantly. Perl's speedy development time
can be a huge competitive advantage.
=back
=head2 Java does away with the need for Perl.
=over 4
=item M:
Perl had its place in the past, but now there's Java and Java will
kill Perl.
=item R:
Java and Perl are actually more complimentary languages then
competitive. Its widely accepted that server side Java solutions such
as C<JServ>, C<JSP> and C<JRUN>, are far slower then mod_perl
solutions (see next myth). Even so, Java is often used as the front
end for server side Perl applications. Unlike Perl, with Java you can
create advanced client side applications. Combined with the strength
of server side Perl these client side Java applications can be made
very powerful.
=back
=head2 Perl can't create advanced client side applications
=over 4
=item R:
True. There are some client side Perl solutions like PerlScript in
MSIE 5.0, but all client side Perl requires the user to have the Perl
interpreter on their local machine. Most users do not have a Perl
interpreter on their local machine. Most Perl programmers who need to
create an advanced client side application use Java as their client
side programming language and Perl as the server side solution.
=back
=head2 ASP makes Perl obsolete as a web programming language.
=over 4
=item M:
With Perl you have to write individual programs for each set of pages.
With ASP you can write simple code directly within HTML pages. ASP is
the Perl killer.
=item R:
There are many solutions which allow you to embed Perl in web pages
just like ASP. In fact, you can actually use Perl IN ASP pages with
PerlScript. Other solutions include: C<Mason>, C<Apache::ASP>,
C<ePerl>, C<embPerl> and C<XPP>. Also, Microsoft and ActiveState have
worked very hard to make Perl run equally well on NT as Unix. You can
even create COM modules in Perl that can be used from within ASP
pages. Some other advantages Perl has over ASP: mod_perl is usually
much faster then ASP, Perl has much more example code and full
programs which are freely downloadable, and Perl is cross platform,
able to run on Solaris, Linux, SCO, Digital Unix, Unix V, AIX, OS2,
VMS MacOS, Win95-98 and NT to name a few.
Also, Benchmarks show that embedded Perl solutions outperform ASP/VB on IIS
by several orders of magnitude. Perl is a much easier language for some
to learn, especially those with a background in C or C++.
=back
=head1 CREDITS
Thanks to the mod_perl list for all of the good information and
criticism. I'd especially like to thank,
=over 4
=item *
Stas Bekman E<lt>[EMAIL PROTECTED]<gt>
=item *
Thornton Prime E<lt>[EMAIL PROTECTED]<gt>
=item *
Chip Turner E<lt>[EMAIL PROTECTED]<gt>
=item *
Clinton E<lt>[EMAIL PROTECTED]<gt>
=item *
Joshua Chamas E<lt>[EMAIL PROTECTED]<gt>
=item *
John Edstrom E<lt>[EMAIL PROTECTED]<gt>
=item *
Rasmus Lerdorf E<lt>[EMAIL PROTECTED]<gt>
=item *
Nedim Cholich E<lt>[EMAIL PROTECTED]<gt>
=item *
Mike Perry E<lt> http://www.icorp.net/icorp/feedback.htm E<gt>
=item *
Finally, I'd like to thank Robert Santos E<lt>[EMAIL PROTECTED]<gt>,
CyberNation's lead Business Development guy for inspiring this
document.
=back
=head1 AUTHOR
Adam Pisoni
=head2 Contact info
email: [EMAIL PROTECTED]
WWW: http://sm.pm.org/
WWW: http://www.cnation.com
=head1 VERSION
Ver 1.04
Tue Aug 5 9:45:00 PST 1999
=cut
1.1 modperl-docs/src/docs/1.0/win32/config.cfg
Index: config.cfg
===================================================================
use vars qw(@c);
@c = (
id => 'win32',
title => "mod_perl on Win32",
abstract => 'Various documents assisting mod_perl users on Win32
platforms',
chapters => [
qw(
win32_binaries.pod
win32_compile.pod
win32_multithread.pod
),
],
);
1.1 modperl-docs/src/docs/1.0/win32/win32_binaries.pod
Index: win32_binaries.pod
===================================================================
=head1 NAME
win32_binaries - obtaining Apache mod_perl-1.xx binaries for Win32
=head1 DESCRIPTION
This document discusses the two major types of binary packages
available for Win32 mod_perl - all-in-one Perl/Apache/mod_perl
binaries, and mod_perl ppm (Perl Package Manager) packages.
=head1 ALL-IN-ONE PACKAGES
There are at least two binary packages for Win32 that contain the
necessary Perl and Apache binaries:
http://www.indigostar.com/
ftp://theoryx5.uwinnipeg.ca/pub/other/perl-win32-bin-x.x.exe
As well as including a number of non-core modules, both of these
packages contain mod_perl. See the documentation on the web sites and
that included with the packages for installation instructions. Both of
these also include an ActiveState-compatible C<ppm> (Perl Package
Manager) utility for adding and upgrading modules.
=head1 PPM Packages
For users of ActivePerl, available from
http://www.activestate.com/
there are also C<PPM> mod_perl packages available. For this, if you
don't already have it, get and install the latest Win32 Apache binary
from
http://httpd.apache.org/
Both ActivePerl and Apache binaries are available as C<MSI> files for
use by the Microsoft Installer - as discussed on the ActiveState site,
users of Windows 95 and 98 may need to obtain this. In installing
these packages, you may find it convenient when transcribing any
Unix-oriented documentation to choose installation directories that do
not have spaces in their names (eg, F<C:\Perl> and F<C:\Apache>).
After installing Perl and Apache, you can then install mod_perl via
the PPM utility. ActiveState does not maintain mod_perl in the ppm
repository, so you must get it from a different location other than
ActiveState's site. One way is simply as (broken over two lines for
readability)
C:\> ppm install
http://theoryx5.uwinnipeg.ca/ppmpackages/mod_perl.ppd
Another way, which will be useful if you plan on installing additional
Apache modules, is to set the repository within the C<ppm> shell
utility as (the C<set repository ...> command has been broken over two
lines for readability):
C:\> ppm
PPM> set repository theoryx5
http://theoryx5.uwinnipeg.ca/cgi-bin/ppmserver?urn:/PPMServer
PPM> install mod_perl
PPM> set save
PPM> quit
C:\>
The C<set save> command saves the C<theoryx5> repository to your PPM
configuration file, so that future PPM sessions will search this
repository, as well as ActiveState's, for requested packages.
The mod_perl PPM package also includes the necessary Apache DLL
C<mod_perl.so>; a post-installation script should be run which will
offer to copy this file to your Apache modules directory (eg,
F<C:\Apache\modules>).
Note that the mod_perl package available from this site will always
use the latest mod_perl sources compiled against the latest official
Apache release; depending on changes made in Apache, you may or may
not be able to use an earlier Apache binary. However, in the Apache
Win32 world it is particularly a good idea to use the latest version,
for bug and security fixes.
=head1 CONFIGURATION
Add this line to F<C:\Apache\conf\httpd.conf>:
LoadModule perl_module modules/mod_perl.so
Be sure that the path to your Perl binary (eg, F<C:\Perl\bin>) is in
your C<PATH> environment variable.
=head2 Registry scripts
Using C<Apache::Registry> to speed up cgi scripts may be done as
follows. Create a directory, for example, F<C:\Apache\mod_perl>, which
will hold your scripts. Insert then in F<C:\Apache\conf\httpd.conf>
the following directives:
Alias /mod_perl/ "/Apache/mod_perl/"
<Location /mod_perl>
SetHandler perl-script
PerlHandler Apache::Registry
Options +ExecCGI
PerlSendHeader On
</Location>
whereby the script would be called as
http://localhost/mod_perl/name_of_script
=head2 Hello World
As you will discover, there is much to mod_perl beyond simple speed-up
of cgi scripts. Here is a simple I<Hello, World> example that
illustrates the use of mod_perl as a content handler. Create a file
F<Hello.pm> as follows:
package Apache::Hello;
use strict;
use Apache::Constants qw(OK);
sub handler {
my $r = shift;
$r->send_http_header;
$r->print("<html><body>Hello World!</body></html>\n");
return OK;
}
1;
and save it in, for example, the F<C:\Perl\site\lib\Apache\>
directory. Next put the following directives in
F<C:\Apache\conf\httpd.conf>:
PerlModule Apache::Hello
<Location /hello>
SetHandler perl-script
PerlHandler Apache::Hello
</Location>
With this, calls to
http://localhost/hello
will use C<Apache::Hello> to deliver the content.
=head1 APACHE MODULES
The C<theorxy5> repository containing the mod_perl ppm package also
contains a number of other Apache modules, such as C<Apache::ASP>,
C<HTML::Embperl>, and C<HTML::Mason>. However, there may be ones you
find that are not available through a repository; in such cases, you
might try sending a message to the maintainer of the repository asking
if a particular package could be included, or you could use the
C<CPAN.pm> module to fetch, build, and install the module - see
C<perldoc CPAN> for details.
=head1 SEE ALSO
L<mod_perl>, L<Apache>, http://perl.apache.org/, especially the guide,
http://take23.org/, http://httpd.apache.org/, and
http://www.activestate.com/.
=cut
1.1 modperl-docs/src/docs/1.0/win32/win32_compile.pod
Index: win32_compile.pod
===================================================================
=head1 NAME
win32_compile - Apache mod_perl-1.xx installation instructions for Win32
=head1 DESCRIPTION
This document discusses how to build, test, configure and
install mod_perl under Win32.
=head1 PREREQUISITES
=over 3
patience - mod_perl is considered alpha under Win32.
MSVC++ 5.0+, Apache version 1.3-dev or higher and Perl 5.004_02 or higher.
As of version 1.24_01, mod_perl will build on Win32 ActivePerls
based on Perl-5.6.x (builds 6xx). For binary compatibility you
should use the same compiler in building mod_perl that was used
to compile your Perl binary; for ActivePerl, this means using VC++ 6.
=back
=head1 BUILDING
Obtain the mod_perl sources from CPAN:
http://www.cpan.org/authors/id/D/DO/DOUGM/mod_perl-1.xx.tar.gz
When unpacked, using Winzip or similar tools, a subdirectory
F<mod_perl-1.xx> will be created.
There are two ways to build mod_perl - with MS Developer Studio,
and through command-line arguments to 'perl Makefile.PL'. In both
cases Apache should previously have been built and installed - if
you are using a binary build of Apache, make sure that you obtain
a binary build that includes the Apache libraries and header files.
=head2 Building with MS Developer Studio
=over 3
=item Setup the Perl side
Run, from a DOS window in the top-level directory of the
mod_perl sources,
perl Makefile.PL
nmake
This will set up the Perl side of mod_perl for the library build.
=item Build mod_perl.so
Using MS developer studio,
select "File -> Open Workspace ...",
select "Files of type [Projects (*.dsp)]"
open mod_perl-x.xx/src/modules/win32/mod_perl.dsp
=item Settings
select "Tools -> Options -> [Directories]"
select "Show directories for: [Include files]", and add
C:\Apache\include
. (should expand to C:\...\mod_perl-x.xx\src\modules\perl)
C:\Perl\lib\Core
select "Project -> Add to Project -> Files", adding:
perl.lib (or perl56.lib) (e.g. C:\perl\lib\Core\perl.lib)
ApacheCore.lib (e.g. C:\Apache\ApacheCore.lib)
select "Build -> Set Active Configuration -> [mod_perl - Win32 Release]"
select "Build -> Build mod_perl.so"
You may see some harmless warnings, which can be reduced (along with
the size of the DLL), by setting:
"Project -> Settings -> [C/C++] -> Category: [Code Generation] ->
Use runtime library: [Multithreaded DLL]
=item Testing
Once mod_perl.so is built you may test mod_perl with:
nmake test
after which, assuming the tests are OK,
nmake install
will install the Perl side of mod_perl. The mod_perl.so file
built under F<mod_perl-1.xx/src/modules/win32/Release> should
be copied to your Apache modules directory (eg, F<C:\Apache\modules>).
=back
=head2 Building with arguments to C<perl Makefile.PL>
Generating the Makefile as, for example,
perl Makefile.PL APACHE_SRC=\Apache INSTALL_DLL=\Apache\modules
will build mod_perl (including mod_perl.so) entirely from
the command line. The arguments accepted include
=over 3
=item APACHE_SRC
This can be one of two values: either the path to the Apache build
directory (eg, F<..\apache_1.3.xx>), or to the installed Apache location
(eg, F<\Apache>). This is used to set the locations of ApacheCore.lib
and the Apache header files.
=item INSTALL_DLL
This gives the location of where to install mod_perl.so
(eg, F<\Apache\modules>). No default is assumed - if this argument
is not given, mod_perl.so must be copied manually.
=item DEBUG
If true (DEBUG=1), a Debug version will be built (this assumes
that a Debug Apache has been built). If false, or not given,
a Release version will be built.
=item EAPI
If true (EAPI=1), EAPI (Extended API) will be defined when
compiling. This is useful when building mod_perl against mod_ssl
patched Apache sources. If false, or not given, EAPI will
not be defined.
=back
After this, running
nmake
nmake test
nmake install
will complete the installation.
This latter method of building mod_perl will also install the
Apache and mod_perl header files, which can then be accessed
through the Apache::src module.
=head1 CONFIGURATION
Add this line to F<C:\Apache\conf\httpd.conf>:
LoadModule perl_module modules/mod_perl.so
Be sure that the path to your Perl binary (eg, F<C:\Perl\bin>)
is in your C<PATH> environment variable.
=head1 SEE ALSO
L<mod_perl>, L<Apache>, http://perl.apache.org/, especially
the guide, and http://take23.org/.
=cut
1.1 modperl-docs/src/docs/1.0/win32/win32_multithread.pod
Index: win32_multithread.pod
===================================================================
=head1 NAME
win32_multithread - discussion of multithreading on Win32 mod_perl-1.xx
=head1 DESCRIPTION
This document discusses the multithreading limitations of
mod_perl-1.xx on Win32.
=head1 The problem
On Win32, mod_perl is effectively single threaded. What this
means is that a single instance of the interpreter is created,
and this is then protected by a server-wide lock that prevents
more than one thread from using the interpreter at any one time.
The fact that this will prevent parallel processing of requests,
including static requests, can have serious implications for
production servers that often must handle concurrent or
long-running requests.
This situation will change with Apache/mod_perl 2.0, which is
based on a multi-process/multi-thread approach using a native
Win32 threads implementation. See
http://perl.apache.org/~dougm/modperl_2.0.html for details.
At the time of writing, Apache-2.0 is in a beta stage of
development. mod_perl-2.0 is being actively developed, including the
Win32 port; if you would like a preview and/or would like to
contribute to the development process, see the documents on obtaining
mod_perl-2.0 by cvs, which can be obtained from mod_perl's home page
at http://perl.apache.org/.
=head1 Does it really matter?
How serious is this? For some people and application classes it may be a
non-problem, assuming the static material issue is handled differently.
Low traffic and single user development sites will likely be
unaffected (though the lattest are likely to experience some surprises
when moving to an environment where requests are no longer serialized
and concurrency kicks in).
If your application is CPU bound, and all requests take roughly the
same time to complete, then having more processing threads than
processors (CPUs) will actually slow things down, because of the
context switching overhead. Note that, even in this case, the current
state of mod_perl will bar owners of multiprocessor Win32 machines
from gaining any load balancing advantage from their superior hardware.
On the other hand, applications dealing with a large service times
spread - say ranging from fractions of a second to a minute and above
- stand to lose a great deal of responsiveness from being single
threaded. The reason is that short requests that happen to be queueued
after long ones will be delayed for the entire duration of the "jobs"
that precede them in the queue; with multitasking they would get a chance
to complete much earlier.
=head1 Workarounds
If you need multithreading on Win32, either because your application
has long running requests, or because you can afford multiprocessor
hardware, and assuming you cannot switch operating systems, you may
want to consider a few workarounds and/or alternatives - which do not
require waiting for 2.0.
You may be able to make Win32 multithreading a non-issue by tuning or
rearranging your application and your architecture (useful tips on
both counts can be found elsewhere in this document). You may be able
to significantly reduce your worst-case timing problems or you may
find that you can move the webserver to a more mod_perl friendly
operating system by using a multi-tier scheme.
If your application needs the full power of the Apache modules (often
the case for people running outside Apache::Registry) you may want to
consider a multi-server load balancing setup which uses mod_rewrite
(or a similar URL partitioning scheme) to spread requests to several web
servers, listening on different ports.
The mod_proxy dual server setup, discussed in the "Strategy" section,
is also a possibility, although people who have tried it have reported
problems with Win32 mod_proxy.
If you code to Apache::Registry (writing CGI compliant code) and can
characterize the time demanded by a request from its URL, you can use
a rewrite-based load balancing with a single server, by sending short
requests to mod_perl while routing longer ones to the pure CGI
environment - on the basis that startup, compilation and init times
will matter less in this case.
If none of the above works for you, then you will have to turn to some
non mod_perl alternatives: this, however, implies giving up on most of
the flexibility of the Apache modules.
For CGI compliant scripts, two possible (portable) alternatives which
are supported in an Apache/perl environment are straight CGI and
FastCGI. In theory a CGI application that runs under mod_perl should
have very few or no problems to run under straight CGI (though its
performance may be unacceptable). A FastCGI port should also be
relatively painless. However, as always, your mileage may vary.
If you do not mind replacing Apache with IIS/PWS, you may want
to experiment with ActiveState's value added PerlEx extension, which
speeds up CGI scripts much in a way similar to what FastCGI
does. PerlEx is transparently supported by CGI.pm, so users of this
package should be more or less covered. (A IIS-FastCGI accelerator is,
regrettably, no longer available.)
=head1 SEE ALSO
http://perl.apache.org and http://httpd.apache.org, especially the
discussion of Apache-2 and modperl-2.
=cut
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