httpd-cvs mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From sl...@apache.org
Subject cvs commit: httpd-2.0/docs/manual stopping.xml stopping.html.en
Date Thu, 15 Aug 2002 23:16:45 GMT
slive       2002/08/15 16:16:44

  Modified:    docs/manual stopping.html.en
  Added:       docs/manual stopping.xml
  Log:
  New XML along with a few small content changes to bring us up to
  the current era.
  
  Revision  Changes    Path
  1.26      +69 -109   httpd-2.0/docs/manual/stopping.html.en
  
  Index: stopping.html.en
  ===================================================================
  RCS file: /home/cvs/httpd-2.0/docs/manual/stopping.html.en,v
  retrieving revision 1.25
  retrieving revision 1.26
  diff -u -d -b -u -r1.25 -r1.26
  --- stopping.html.en	25 Jul 2002 21:46:38 -0000	1.25
  +++ stopping.html.en	15 Aug 2002 23:16:44 -0000	1.26
  @@ -1,74 +1,51 @@
  -<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
  -    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
  -
  -<html xmlns="http://www.w3.org/1999/xhtml">
  -  <head>
  -    <meta name="generator" content="HTML Tidy, see www.w3.org" />
  -
  -    <title>Stopping and Restarting the Server</title>
  -  </head>
  -  <!-- Background white, links blue (unvisited), navy (visited), red (active) -->
  -
  -  <body bgcolor="#FFFFFF" text="#000000" link="#0000FF"
  -  vlink="#000080" alink="#FF0000">
  -    <!--#include virtual="header.html" -->
  -
  -    <h1 align="center">Stopping and Restarting the Server</h1>
  -
  +<html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><!--
  +        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  +              This file is generated from xml source: DO NOT EDIT
  +        XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
  +      --><title>Stopping and Restarting - Apache HTTP Server</title><link
href="./style/manual.css" type="text/css" rel="stylesheet"></head><body><blockquote><div
align="center"><img src="./images/sub.gif" alt="[APACHE DOCUMENTATION]"><h3>Apache
HTTP Server Version 2.0</h3></div><h1 align="center">Stopping and Restarting</h1>
       <p>This document covers stopping and restarting Apache on
  -    Unix-like systems. Windows users should see <a
  -    href="platform/windows.html#signal">Signalling Apache when
  +    Unix-like systems. Windows users should see <a href="platform/windows.html#signal">Signalling
Apache when
       running</a>.</p>
  +<ul><li><a href="#introduction">Introduction</a></li><li><a
href="#term">Stop Now</a></li><li><a href="#graceful">Graceful
Restart</a></li><li><a href="#hup">Restart Now</a></li><li><a
href="#race">Appendix: signals and race conditions</a></li></ul><hr><h2><a
name="introduction">Introduction</a></h2>
   
  -    <p>You will notice many <code>httpd</code> executables running
  -    on your system, but you should not send signals to any of them
  -    except the parent, whose pid is in the <a
  -    href="mod/mpm_common.html#pidfile">PidFile</a>. That is to say you
  -    shouldn't ever need to send signals to any process except the
  -    parent. There are three signals that you can send the parent:
  -    <code>TERM</code>, <code>HUP</code>, and <code>USR1</code>,
  -    which will be described in a moment.</p>
  +    <p>You will notice many <code>httpd</code> executables running on
  +    your system, but you should not send signals to any of them except
  +    the parent, whose pid is in the <a href="./mod/mpm_common.html#pidfile" class="directive"><code
class="directive">PidFile</code></a>. That is to say you shouldn't ever
  +    need to send signals to any process except the parent. There are
  +    three signals that you can send the parent: <code>TERM</code>,
  +    <code>HUP</code>, and <code>USR1</code>, which will be described
  +    in a moment.</p>
   
       <p>To send a signal to the parent you should issue a command
       such as:</p>
   
  -    <blockquote>
  -<pre>
  -    kill -TERM `cat /usr/local/apache/logs/httpd.pid`
  -</pre>
  -    </blockquote>
  -    You can read about its progress by issuing: 
  +<blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>kill
-TERM `cat /usr/local/apache/logs/httpd.pid`</code></td></tr></table></blockquote>
   
  -    <blockquote>
  -<pre>
  -    tail -f /usr/local/apache/logs/error_log
  -</pre>
  -    </blockquote>
  -    Modify those examples to match your <a
  -    href="mod/core.html#serverroot">ServerRoot</a> and <a
  -    href="mod/mpm_common.html#pidfile">PidFile</a> settings. 
  +    <p>You can read about its progress by issuing:</p>
   
  -    <p>A shell script called <a
  -    href="programs/apachectl.html">apachectl</a> is provided which
  -    automates the processing of signalling Apache. For details
  -    about this script, see the documentation on <a
  -    href="invoking.html">starting Apache</a>.</p>
  +<blockquote><table cellpadding="10"><tr><td bgcolor="#eeeeee"><code>tail
-f /usr/local/apache/logs/error_log</code></td></tr></table></blockquote>
   
  -    <h3>Stop Now</h3>
  +    <p>Modify those examples to match your <a href="./mod/core.html#serverroot"
class="directive"><code class="directive">ServerRoot</code></a> and <a
href="./mod/mpm_common.html#pidfile" class="directive"><code class="directive">PidFile</code></a>
settings.</p>
   
  -    <p><strong>Signal:</strong> TERM<br />
  -     <code>apachectl stop</code></p>
  +    <p>A shell script called <a href="programs/apachectl.html">apachectl</a>
is provided which
  +    automates the processing of signalling Apache. For details
  +    about this script, see the documentation on <a href="invoking.html">starting
Apache</a>.</p>
  +<h2><a name="term">Stop Now</a></h2>
  +
  +<dl><dt>Signal: TERM</dt>
  +<dd><code>apachectl stop</code></dd>
  +</dl>
   
       <p>Sending the <code>TERM</code> signal to the parent causes it
       to immediately attempt to kill off all of its children. It may
       take it several seconds to complete killing off its children.
       Then the parent itself exits. Any requests in progress are
       terminated, and no further requests are served.</p>
  +<h2><a name="graceful">Graceful Restart</a></h2>
   
  -    <h3>Graceful Restart</h3>
  -
  -    <p><strong>Signal:</strong> USR1<br />
  -     <code>apachectl graceful</code></p>
  +<dl><dt>Signal: USR1</dt>
  +<dd><code>apachectl graceful</code></dd>
  +</dl>
   
       <p>The <code>USR1</code> signal causes the parent process to
       <em>advise</em> the children to exit after their current
  @@ -78,26 +55,24 @@
       replaces it with a child from the new <em>generation</em> of
       the configuration, which begins serving new requests
       immediately.</p>
  -    <i>On certain platforms that do not allow USR1 to be used for a
  +
  +    <blockquote><table><tr><td bgcolor="#e0e5f5">On certain platforms
that do not allow USR1 to be used for a
       graceful restart, an alternative signal may be used (such as
  -    WINCH). apachectl graceful will send the right signal for your
  -    platform.</i> 
  +    WINCH). The command <code>apachectl graceful</code> will send the
  +    right signal for your platform.</td></tr></table></blockquote>
   
  -    <p>This code is designed to always respect the <a
  -    href="mod/mpm_common.html#maxclients">MaxClients</a>, <a
  -    href="mod/prefork.html#minspareservers">MinSpareServers</a>,
  -    and <a
  -    href="mod/prefork.html#maxspareservers">MaxSpareServers</a>
  -    settings. Furthermore, it respects <a
  -    href="mod/mpm_common.html#startservers">StartServers</a> in the
  -    following manner: if after one second at least StartServers new
  -    children have not been created, then create enough to pick up
  -    the slack. This is to say that the code tries to maintain both
  -    the number of children appropriate for the current load on the
  -    server, and respect your wishes with the StartServers
  -    parameter.</p>
  +    <p>This code is designed to always respect the process control
  +    directive of the MPMs, so the number of processes and threads
  +    available to serve clients will be maintained at the appropriate
  +    values throughout the restart process.  Furthermore, it respects
  +    <a href="./mod/mpm_common.html#startservers" class="directive"><code class="directive">StartServers</code></a>
in the
  +    following manner: if after one second at least <a href="./mod/mpm_common.html#startservers"
class="directive"><code class="directive">StartServers</code></a> new
children have not
  +    been created, then create enough to pick up the slack. Hence the
  +    code tries to maintain both the number of children appropriate for
  +    the current load on the server, and respect your wishes with the
  +    StartServers parameter.</p>
   
  -    <p>Users of the <a href="mod/mod_status.html">status module</a>
  +    <p>Users of the <code><a href="./mod/mod_status.html">mod_status</a></code>
       will notice that the server statistics are <strong>not</strong>
       set to zero when a <code>USR1</code> is sent. The code was
       written to both minimize the time in which the server is unable
  @@ -120,7 +95,7 @@
       low bandwidth links then you could wait 15 minutes before doing
       anything with the old log.</p>
   
  -    <p><strong>Note:</strong> If your configuration file has errors
  +    <blockquote><table><tr><td bgcolor="#e0e5f5">If your configuration
file has errors
       in it when you issue a restart then your parent will not
       restart, it will exit with an error. In the case of graceful
       restarts it will also leave children running when it exits.
  @@ -129,8 +104,7 @@
       attempt to restart the server -- it will not be able to bind to
       its listening ports. Before doing a restart, you can check the
       syntax of the configuration files with the <code>-t</code>
  -    command line argument (see <a
  -    href="programs/httpd.html">httpd</a>). This still will not
  +    command line argument (see <a href="programs/httpd.html">httpd</a>). This
still will not
       guarantee that the server will restart correctly. To check the
       semantics of the configuration files as well as the syntax, you
       can try starting httpd as a non-root user. If there are no
  @@ -138,12 +112,12 @@
       because it's not root (or because the currently running httpd
       already has those ports bound). If it fails for any other
       reason then it's probably a config file error and the error
  -    should be fixed before issuing the graceful restart.</p>
  -
  -    <h3>Restart Now</h3>
  +    should be fixed before issuing the graceful restart.</td></tr></table></blockquote>
  +<h2><a name="hup">Restart Now</a></h2>
   
  -    <p><strong>Signal:</strong> HUP<br />
  -     <code>apachectl restart</code></p>
  +<dl><dt>Signal: HUP</dt>
  +<dd><code>apachectl restart</code></dd>
  +</dl>
   
       <p>Sending the <code>HUP</code> signal to the parent causes it
       to kill off its children like in <code>TERM</code> but the
  @@ -151,16 +125,14 @@
       re-opens any log files. Then it spawns a new set of children
       and continues serving hits.</p>
   
  -    <p>Users of the <a href="mod/mod_status.html">status module</a>
  +    <p>Users of <code><a href="./mod/mod_status.html">mod_status</a></code>
       will notice that the server statistics are set to zero when a
       <code>HUP</code> is sent.</p>
   
  -    <p><strong>Note:</strong> If your configuration file has errors
  -    in it when you issue a restart then your parent will not
  -    restart, it will exit with an error. See below for a method of
  -    avoiding this.</p>
  -
  -    <h3>Appendix: signals and race conditions</h3>
  +<blockquote><table><tr><td bgcolor="#e0e5f5">If your configuration
file has errors in it when you issue a
  +restart then your parent will not restart, it will exit with an
  +error. See above for a method of avoiding this.</td></tr></table></blockquote>
  +<h2><a name="race">Appendix: signals and race conditions</a></h2>
   
       <p>Prior to Apache 1.2b9 there were several <em>race
       conditions</em> involving the restart and die signals (a simple
  @@ -171,25 +143,16 @@
       be noted that there still do exist race conditions on certain
       architectures.</p>
   
  -    <p>Architectures that use an on disk <a
  -    href="mod/mpm_common.html#scoreboardfile">ScoreBoardFile</a> have the
  -    potential to corrupt their scoreboards. This can result in the
  -    "bind: Address already in use" (after <code>HUP</code>) or
  -    "long lost child came home!" (after <code>USR1</code>). The
  -    former is a fatal error, while the latter just causes the
  -    server to lose a scoreboard slot. So it might be advisable to
  -    use graceful restarts, with an occasional hard restart. These
  -    problems are very difficult to work around, but fortunately
  -    most architectures do not require a scoreboard file. See the <a
  -    href="mod/mpm_common.html#scoreboardfile">ScoreBoardFile</a>
  -    documentation for a architecture uses it.</p>
  -
  -    <p><code>NEXT</code> and <code>MACHTEN</code> (68k only)
have
  -    small race conditions which can cause a restart/die signal to
  -    be lost, but should not cause the server to do anything
  -    otherwise problematic. 
  -    <!-- they don't have sigaction, or we're not using it -djg -->
  -    </p>
  +    <p>Architectures that use an on disk <a href="./mod/mpm_common.html#scoreboardfile"
class="directive"><code class="directive">ScoreBoardFile</code></a> have
the potential
  +    to corrupt their scoreboards. This can result in the "bind:
  +    Address already in use" (after <code>HUP</code>) or "long lost
  +    child came home!" (after <code>USR1</code>). The former is a fatal
  +    error, while the latter just causes the server to lose a
  +    scoreboard slot. So it might be advisable to use graceful
  +    restarts, with an occasional hard restart. These problems are very
  +    difficult to work around, but fortunately most architectures do
  +    not require a scoreboard file. See the <a href="./mod/mpm_common.html#scoreboardfile"
class="directive"><code class="directive">ScoreBoardFile</code></a> documentation
for a
  +    architecture uses it.</p>
   
       <p>All architectures have a small race condition in each child
       involving the second and subsequent requests on a persistent
  @@ -202,7 +165,4 @@
       -- in a test case the server was restarted twenty times per
       second and clients successfully browsed the site without
       getting broken images or empty documents. </p>
  -    <!--#include virtual="footer.html" -->
  -  </body>
  -</html>
  -
  +<hr></blockquote><h3 align="center">Apache HTTP Server Version 2.0</h3><a
href="./"><img src="./images/index.gif" alt="Index"></a><a href="./"><img
src="./images/home.gif" alt="Home"></a></body></html>
  \ No newline at end of file
  
  
  
  1.1                  httpd-2.0/docs/manual/stopping.xml
  
  Index: stopping.xml
  ===================================================================
  <?xml version='1.0' encoding='UTF-8' ?>
  <!DOCTYPE manualpage SYSTEM "./style/manualpage.dtd">
  <?xml-stylesheet type="text/xsl" href="./style/manual.en.xsl"?>
  <manualpage>
  <relativepath href="."/>
  
    <title>Stopping and Restarting</title>
  
  <summary>
      <p>This document covers stopping and restarting Apache on
      Unix-like systems. Windows users should see <a
      href="platform/windows.html#signal">Signalling Apache when
      running</a>.</p>
  </summary>
  
  <section id="introduction"><title>Introduction</title>
  
      <p>You will notice many <code>httpd</code> executables running on
      your system, but you should not send signals to any of them except
      the parent, whose pid is in the <directive
      module="mpm_common">PidFile</directive>. That is to say you shouldn't ever
      need to send signals to any process except the parent. There are
      three signals that you can send the parent: <code>TERM</code>,
      <code>HUP</code>, and <code>USR1</code>, which will be described
      in a moment.</p>
  
      <p>To send a signal to the parent you should issue a command
      such as:</p>
  
  <example>kill -TERM `cat /usr/local/apache/logs/httpd.pid`</example>
  
      <p>You can read about its progress by issuing:</p>
  
  <example>tail -f /usr/local/apache/logs/error_log</example>
  
      <p>Modify those examples to match your <directive
      module="core">ServerRoot</directive> and <directive
      module="mpm_common">PidFile</directive> settings.</p>
  
      <p>A shell script called <a
      href="programs/apachectl.html">apachectl</a> is provided which
      automates the processing of signalling Apache. For details
      about this script, see the documentation on <a
      href="invoking.html">starting Apache</a>.</p>
  </section>
  
  <section id="term"><title>Stop Now</title>
  
  <dl><dt>Signal: TERM</dt>
  <dd><code>apachectl stop</code></dd>
  </dl>
  
      <p>Sending the <code>TERM</code> signal to the parent causes it
      to immediately attempt to kill off all of its children. It may
      take it several seconds to complete killing off its children.
      Then the parent itself exits. Any requests in progress are
      terminated, and no further requests are served.</p>
  </section>
  
  <section id="graceful"><title>Graceful Restart</title>
  
  <dl><dt>Signal: USR1</dt>
  <dd><code>apachectl graceful</code></dd>
  </dl>
  
      <p>The <code>USR1</code> signal causes the parent process to
      <em>advise</em> the children to exit after their current
      request (or to exit immediately if they're not serving
      anything). The parent re-reads its configuration files and
      re-opens its log files. As each child dies off the parent
      replaces it with a child from the new <em>generation</em> of
      the configuration, which begins serving new requests
      immediately.</p>
  
      <note>On certain platforms that do not allow USR1 to be used for a
      graceful restart, an alternative signal may be used (such as
      WINCH). The command <code>apachectl graceful</code> will send the
      right signal for your platform.</note>
  
      <p>This code is designed to always respect the process control
      directive of the MPMs, so the number of processes and threads
      available to serve clients will be maintained at the appropriate
      values throughout the restart process.  Furthermore, it respects
      <directive module="mpm_common">StartServers</directive> in the
      following manner: if after one second at least <directive
      module="mpm_common">StartServers</directive> new children have not
      been created, then create enough to pick up the slack. Hence the
      code tries to maintain both the number of children appropriate for
      the current load on the server, and respect your wishes with the
      StartServers parameter.</p>
  
      <p>Users of the <module>mod_status</module>
      will notice that the server statistics are <strong>not</strong>
      set to zero when a <code>USR1</code> is sent. The code was
      written to both minimize the time in which the server is unable
      to serve new requests (they will be queued up by the operating
      system, so they're not lost in any event) and to respect your
      tuning parameters. In order to do this it has to keep the
      <em>scoreboard</em> used to keep track of all children across
      generations.</p>
  
      <p>The status module will also use a <code>G</code> to indicate
      those children which are still serving requests started before
      the graceful restart was given.</p>
  
      <p>At present there is no way for a log rotation script using
      <code>USR1</code> to know for certain that all children writing
      the pre-restart log have finished. We suggest that you use a
      suitable delay after sending the <code>USR1</code> signal
      before you do anything with the old log. For example if most of
      your hits take less than 10 minutes to complete for users on
      low bandwidth links then you could wait 15 minutes before doing
      anything with the old log.</p>
  
      <note>If your configuration file has errors
      in it when you issue a restart then your parent will not
      restart, it will exit with an error. In the case of graceful
      restarts it will also leave children running when it exits.
      (These are the children which are "gracefully exiting" by
      handling their last request.) This will cause problems if you
      attempt to restart the server -- it will not be able to bind to
      its listening ports. Before doing a restart, you can check the
      syntax of the configuration files with the <code>-t</code>
      command line argument (see <a
      href="programs/httpd.html">httpd</a>). This still will not
      guarantee that the server will restart correctly. To check the
      semantics of the configuration files as well as the syntax, you
      can try starting httpd as a non-root user. If there are no
      errors it will attempt to open its sockets and logs and fail
      because it's not root (or because the currently running httpd
      already has those ports bound). If it fails for any other
      reason then it's probably a config file error and the error
      should be fixed before issuing the graceful restart.</note>
  </section>
  
  <section id="hup"><title>Restart Now</title>
  
  <dl><dt>Signal: HUP</dt>
  <dd><code>apachectl restart</code></dd>
  </dl>
  
      <p>Sending the <code>HUP</code> signal to the parent causes it
      to kill off its children like in <code>TERM</code> but the
      parent doesn't exit. It re-reads its configuration files, and
      re-opens any log files. Then it spawns a new set of children
      and continues serving hits.</p>
  
      <p>Users of <module>mod_status</module>
      will notice that the server statistics are set to zero when a
      <code>HUP</code> is sent.</p>
  
  <note>If your configuration file has errors in it when you issue a
  restart then your parent will not restart, it will exit with an
  error. See above for a method of avoiding this.</note>
  </section>
  
  <section id="race"><title>Appendix: signals and race conditions</title>
  
      <p>Prior to Apache 1.2b9 there were several <em>race
      conditions</em> involving the restart and die signals (a simple
      description of race condition is: a time-sensitive problem, as
      in if something happens at just the wrong time it won't behave
      as expected). For those architectures that have the "right"
      feature set we have eliminated as many as we can. But it should
      be noted that there still do exist race conditions on certain
      architectures.</p>
  
      <p>Architectures that use an on disk <directive
      module="mpm_common">ScoreBoardFile</directive> have the potential
      to corrupt their scoreboards. This can result in the "bind:
      Address already in use" (after <code>HUP</code>) or "long lost
      child came home!" (after <code>USR1</code>). The former is a fatal
      error, while the latter just causes the server to lose a
      scoreboard slot. So it might be advisable to use graceful
      restarts, with an occasional hard restart. These problems are very
      difficult to work around, but fortunately most architectures do
      not require a scoreboard file. See the <directive
      module="mpm_common">ScoreBoardFile</directive> documentation for a
      architecture uses it.</p>
  
      <p>All architectures have a small race condition in each child
      involving the second and subsequent requests on a persistent
      HTTP connection (KeepAlive). It may exit after reading the
      request line but before reading any of the request headers.
      There is a fix that was discovered too late to make 1.2. In
      theory this isn't an issue because the KeepAlive client has to
      expect these events because of network latencies and server
      timeouts. In practice it doesn't seem to affect anything either
      -- in a test case the server was restarted twenty times per
      second and clients successfully browsed the site without
      getting broken images or empty documents. </p>
  </section>
  
  </manualpage>
  
  

Mime
View raw message