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From Marc Slemko <m...@hyperreal.com>
Subject cvs commit: apache/htdocs/manual/misc FAQ.html
Date Fri, 11 Apr 1997 03:43:45 GMT
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
  ===================================================================
  RCS file: /export/home/cvs/apache/htdocs/manual/misc/FAQ.html,v
  retrieving revision 1.17
  retrieving revision 1.18
  diff -C3 -r1.17 -r1.18
  *** FAQ.html	1997/04/11 03:36:58	1.17
  --- FAQ.html	1997/04/11 03:43:43	1.18
  ***************
  *** 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>
    <!-- Stuff to Add:						    -->
  --- 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>
    <!-- Stuff to Add:						    -->
  ***************
  *** 522,528 ****
      <HR>
     </LI>
     <LI><A
  !       NAME="multiviews"
         ><STRONG>Why can't I run more than &lt;<EM>n</EM>&gt;
          virtual hosts?</STRONG></A>
      <P>
  --- 522,528 ----
      <HR>
     </LI>
     <LI><A
  !       NAME="fdlim"
         ><STRONG>Why can't I run more than &lt;<EM>n</EM>&gt;
          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 &lt;<EM>n</EM>&gt; 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>&quot;Don't do that&quot; - 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 &lt;<EM>n</EM>&gt; 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>&quot;Don't do that&quot; - try to run with fewer virtual hosts
       </LI>
  
  
  

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