Not much, just a few problems solved. Comments are welcome.
NAME
ModPerl2::Tools - a few hopefully useful tools
SYNOPSIS
use ModPerl2::Tools;
ModPerl2::Tools::spawn +{keep_fd=>[3,4,7], survive=>1}, sub {...};
ModPerl2::Tools::spawn +{keep_fd=>[3,4,7], survive=>1}, qw/bash -c .../;
ModPerl2::Tools::safe_die $status;
$r->safe_die($status);
$f->safe_die($status);
$content=ModPerl2::Tools::fetch_url $url;
$content=$r->fetch_url($url);
INSTALLATION
perl Makefile.PL
make
make test
make install
DESCRIPTION
This module is a collection of functions and methods that I found useful
when working with "mod_perl". I work mostly under Linux. So, I don't
expect all of these functions to work on other operating systems.
Forking off long running processes
Sometimes one needs to spawn off a long running process as the result of
a request. Under modperl this is not as simple as calling "fork" because
that way all open file descriptors would be inherited by the child and,
more subtle, the long running process would be killed when the
administrator shuts down the web server. The former is usually
considered a security issue, the latter a design decision.
There is already $r->spawn_proc_prog that serves a similar purpose as
the "spawn" function. However, "spawn_proc_prog" is not usable for long
running processes because it kills the children after a certain timeout.
Solution
$pid=ModPerl2::Tools::spawn \%options, $subroutine, @parameters;
or
$pid=ModPerl2::Tools::spawn \%options, @command_line;
"spawn" expects as the first parameter an options hash reference. The
second parameter may be a code reference or a string.
In case of a code ref no other program is executed but the subroutine is
called instead. The remaining parameters are passed to this function.
Note, the perl environment under modperl differs in certain ways from a
normal perl environment. For example %ENV is not bound to the C-level
"environ". These modifications are not undone by this module. So, it's
generally better to execute another perl interpreter instead of using
the $subroutine feature.
The options parameter accepts these options:
keep_fd => \...@fds
here an array of file descriptor numbers (not file handles) is
expected. All other file descriptors except for the listed and file
descriptor 2 (STDERR) are closed before calling $subroutine or
executing @command_line.
survive => $boolean
if passed "false" the created process will be killed when Apache
shuts down. if true it will survive an Apache restart.
The return code on success is the PID of the process. On failure "undef"
or an empty string is returned.
The created process is not related as a child process to the current
apache child.
Serving "ErrorDocument"s
Triggering "ErrorDocument"s from a registry script or even more from an
output filter is not simple. The normal way as a handler is
return Apache2::Const::STATUS;
This does not work for registry scripts. An output filter even if it
returns a status can trigger only a "SERVER_ERROR".
The main interface to enter standard error processing in Apache is
"ap_die()" at C-level. Its Perl interface is hidden in Apache2::HookRun.
There is one case when an error message cannot be sent to the user. This
happens if the HTTP headers are already on the wire. Then it is too
late.
The various flavors of "safe_die()" take this into account.
ModPerl2::Tools::safe_die $status
This function is designed to be called from registry scripts. It
uses Apache2::RequestUtil->request to fetch the current request
object. So,
PerlOption +GlobalRequest
must be enabled.
Usage example:
ModPerl2::Tools::safe_die 401;
exit 0;
$r->safe_die($status)
$f->safe_die($status)
These 2 methods are to be used if a request object or a filter
object are available.
Usage from within a filter:
package My::Filter;
use strict;
use warnings;
use ModPerl2::Tools;
use base 'Apache2::Filter';
sub handler : FilterRequestHandler {
my ($f, $bb)=...@_;
return $f->safe_die(410);
}
The filter flavor removes the current filter from the request's
output filter chain.
Fetching the content of another document
Sometimes a handler or a filter needs the content of another document in
the web server's realm. Apache provides subrequests for this purpose.
The 2 "fetch_url" variants use a subrequest to fetch the content of
another document. The document can even be fetched via "mod_proxy" from
another server. However, fetching a document directly as with LWP for
example is not (yet) possible.
"ModPerl2::Tools::fetch_url" needs
PerlOption +GlobalRequest
Usage:
$content=ModPerl2::Tools::fetch_url '/some/where?else=42';
$content=$r->fetch_url('/some/where?else=42');
EXPORTS
None.
SEE ALSO
<http://perl.apache.org>
AUTHOR
Torsten Förtsch, <[email protected]>
COPYRIGHT AND LICENSE
Copyright (C) 2010 by Torsten Förtsch
This library is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
Torsten Förtsch
--
Need professional modperl support? Hire me! (http://foertsch.name)
Like fantasy? http://kabatinte.net
