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Diffstat (limited to 'docs/manual/stopping.html.en')
| -rw-r--r-- | docs/manual/stopping.html.en | 84 |
1 files changed, 42 insertions, 42 deletions
diff --git a/docs/manual/stopping.html.en b/docs/manual/stopping.html.en index 673d81beb3..d5c2e0d154 100644 --- a/docs/manual/stopping.html.en +++ b/docs/manual/stopping.html.en @@ -13,34 +13,34 @@ ALINK="#FF0000" > <!--#include virtual="header.html" --> -<h1 ALIGN="CENTER">Stopping and Restarting Apache</h1> +<h1 ALIGN="CENTER">Stopping and Restarting Apache</H1> -<p>You will notice many <code>httpd</code> executables running on your system, +<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/core.html#pidfile">PidFile</a>. That is to +pid is in the <A HREF="mod/core.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 +<CODE>TERM</CODE>, <CODE>HUP</CODE>, and <CODE>USR1</CODE>, which will be described in a moment. -<p>To send a signal to the parent you should issue a command such as: -<blockquote><pre> +<P>To send a signal to the parent you should issue a command such as: +<BLOCKQUOTE><PRE> kill -TERM `cat /usr/local/apache/logs/httpd.pid` -</pre></blockquote> +</PRE></BLOCKQUOTE> You can read about its progress by issuing: -<blockquote><pre> +<BLOCKQUOTE><PRE> tail -f /usr/local/apache/logs/error_log -</pre></blockquote> +</PRE></BLOCKQUOTE> Modify those examples to match your -<a href="mod/core.html#serverroot">ServerRoot</a> and -<a href="mod/core.html#pidfile">PidFile</a> settings. +<A HREF="mod/core.html#serverroot">ServerRoot</A> and +<A HREF="mod/core.html#pidfile">PidFile</A> settings. <h3>TERM Signal: stop now</h3> -<p>Sending the <code>TERM</code> signal to the parent causes it to +<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 @@ -48,67 +48,67 @@ further requests are served. <h3>HUP Signal: restart now</h3> -<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 +<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>Users of the -<a href="mod/mod_status.html">status module</a> +<P>Users of the +<A HREF="mod/mod_status.html">status module</A> will notice that the server statistics are -set to zero when a <code>HUP</code> is sent. +set to zero when a <CODE>HUP</CODE> is sent. -<p><b>Note:</b> If your configuration file has errors in it when you issue a +<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. <h3>USR1 Signal: graceful restart</h3> -<p><b>Note:</b> prior to release 1.2b9 this code is quite unstable and +<P><STRONG>Note:</STRONG> prior to release 1.2b9 this code is quite unstable and shouldn't be used at all. -<p>The <code>USR1</code> signal causes the parent process to <i>advise</i> +<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 <i>generation</i> of the +replaces it with a child from the new <EM>generation</EM> of the configuration, which begins serving new requests immediately. -<p>This code is designed to always respect the -<a href="mod/core.html#maxclients">MaxClients</a>, -<a href="mod/core.html#minspareservers">MinSpareServers</a>, -and <a href="mod/core.html#maxspareservers">MaxSpareServers</a> settings. -Furthermore, it respects <a href="mod/core.html#startservers">StartServers</a> +<P>This code is designed to always respect the +<A HREF="mod/core.html#maxclients">MaxClients</A>, +<A HREF="mod/core.html#minspareservers">MinSpareServers</A>, +and <A HREF="mod/core.html#maxspareservers">MaxSpareServers</A> settings. +Furthermore, it respects <A HREF="mod/core.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>Users of the -<a href="mod/mod_status.html">status module</a> +<P>Users of the +<A HREF="mod/mod_status.html">status module</A> will notice that the server statistics -are <b>not</b> set to zero when a <code>USR1</code> is sent. The code +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 <i>scoreboard</i> used to keep track +to do this it has to keep the <EM>scoreboard</EM> used to keep track of all children across generations. -<p>The status module will also use a <code>G</code> to indicate those +<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>At present there is no way for a log rotation script using -<code>USR1</code> to know for certain that all children writing the +<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 +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><b>Note:</b> If your configuration file has errors in it when you issue a +<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. In the case of graceful restarts it will also leave children running when it exits. (These are @@ -124,7 +124,7 @@ error and the error should be fixed before issuing the graceful restart. <h3>Appendix: signals and race conditions</h3> -<p>Prior to Apache 1.2b9 there were several <i>race conditions</i> +<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 @@ -132,11 +132,11 @@ 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>Architectures that use an on disk -<a href="mod/core.html#scoreboardfile">ScoreBoardFile</a> +<P>Architectures that use an on disk +<A HREF="mod/core.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 +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 @@ -144,13 +144,13 @@ around, but fortunately most architectures do not require a scoreboard file. See the ScoreBoardFile documentation for a method to determine if your architecture uses it. -<p><code>NEXT</code> and <code>MACHTEN</code> (68k only) have small race +<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>All architectures have a small race condition in each child involving +<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 |