marc 97/04/10 20:43:44
Modified: htdocs/manual/misc FAQ.html
Log:
Expand the section on fd limits a bit.
Revision Changes Path
1.18 +24 -10 apache/htdocs/manual/misc/FAQ.html
Index: FAQ.html
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RCS file: /export/home/cvs/apache/htdocs/manual/misc/FAQ.html,v
retrieving revision 1.17
retrieving revision 1.18
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*** FAQ.html 1997/04/11 03:36:58 1.17
--- FAQ.html 1997/04/11 03:43:43 1.18
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*** 8,14 ****
<!--#include virtual="header.html" -->
<H1>Apache Server Frequently Asked Questions</H1>
<P>
! $Revision: 1.17 $ ($Date: 1997/04/11 03:36:58 $)
</P>
<H2>The Questions</H2>
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--- 8,14 ----
<!--#include virtual="header.html" -->
<H1>Apache Server Frequently Asked Questions</H1>
<P>
! $Revision: 1.18 $ ($Date: 1997/04/11 03:43:43 $)
</P>
<H2>The Questions</H2>
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***************
*** 522,528 ****
<HR>
</LI>
<LI><A
! NAME="multiviews"
><STRONG>Why can't I run more than <<EM>n</EM>>
virtual hosts?</STRONG></A>
<P>
--- 522,528 ----
<HR>
</LI>
<LI><A
! NAME="fdlim"
><STRONG>Why can't I run more than <<EM>n</EM>>
virtual hosts?</STRONG></A>
<P>
***************
*** 530,559 ****
resource limitations. One of these is the <EM>per</EM>-process limit
on <STRONG>file descriptors</STRONG>, and that's almost always the
cause of problems seen when adding virtual hosts. In this
! case, it is not actually Apache that's encountering the problem, but
! typically some library routine (such as <SAMP>gethostbyname()</SAMP>)
which needs file descriptors and doesn't complain intelligibly when it
can't get them.
</P>
<P>
! Each virtual host requires several file descriptors for housekeeping
! functions, in addition to those actually used to serve files to
! clients.
</P>
<P>
Typical values for <<EM>n</EM>> that we've seen are in
the neighbourhoods of 128 or 250. When the server bumps into the file
descriptor limit, it may dump core with a SIGSEGV, or it might just
hang, or it may limp along and you'll see (possibly meaningful) errors
! in the error log.
</P>
<P>
As to what you can do about this:
</P>
<OL>
<LI>Increase the number of file descriptors available to the server
! (see your system's documentation on the <SAMP>limit</SAMP> or
! <SAMP>ulimit</SAMP> commands)
</LI>
<LI>"Don't do that" - try to run with fewer virtual hosts
</LI>
--- 530,573 ----
resource limitations. One of these is the <EM>per</EM>-process limit
on <STRONG>file descriptors</STRONG>, and that's almost always the
cause of problems seen when adding virtual hosts. In this
! case, it is often not actually Apache that's encountering the problem,
but
! some library routine (such as <SAMP>gethostbyname()</SAMP>)
which needs file descriptors and doesn't complain intelligibly when it
can't get them.
</P>
<P>
! Each log file requires a file descriptor, which means that if you are
! using seperate access and error logs for each virtual host each
! virtual host needs two file descriptors. Each
! <A HREF="../mod/core.html#listen"> Listen</A> directive also needs
! a file descriptor.
</P>
<P>
Typical values for <<EM>n</EM>> that we've seen are in
the neighbourhoods of 128 or 250. When the server bumps into the file
descriptor limit, it may dump core with a SIGSEGV, or it might just
hang, or it may limp along and you'll see (possibly meaningful) errors
! in the error log. One common problem that occurs when you run into
! a file descriptor limit is that CGI scripts stop being executed
! properly at times.
</P>
<P>
As to what you can do about this:
</P>
<OL>
+ <LI>Reduce the number of <A HREF="../mod/core.html#listen">Listen</A>
+ directives. If there are no other servers running on the machine
+ and all of them are running on the same port, you normally don't
+ need any Listen directives at all.
+ <LI>Reduce the number of log files. You can use
+ <A HREF="../mod/mod_log_config.html">log_mod_config</A> to log
+ all requests to a single log file while including the name
+ of the virtual host in the log file.
<LI>Increase the number of file descriptors available to the server
! (see your system's documentation on the <SAMP>limit</SAMP> or
! <SAMP>ulimit</SAMP> commands). For some systems, information on
! how to do this is available in the <A HREF="perf.html">performance
! hints</A> page.
</LI>
<LI>"Don't do that" - try to run with fewer virtual hosts
</LI>
