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| author |   hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
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| committer | hongbotian <hongbo.tianhongbo@huawei.com> | 2015-11-30 01:45:08 -0500 |
| commit | e8ec7aa8e38a93f5b034ac74cebce5de23710317 (patch) | |
| tree | aa031937bf856c1f8d6ad7877b8d2cb0224da5ef /rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en | |
| parent | cc40af334e619bb549038238507407866f774f8f (diff) | |
upload http
JIRA: BOTTLENECK-10
Change-Id: I7598427ff904df438ce77c2819ee48ac75ffa8da
Signed-off-by: hongbotian <hongbo.tianhongbo@huawei.com>
Diffstat (limited to 'rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en')
| -rw-r--r-- | rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en | 235 |
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diff --git a/rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en b/rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en new file mode 100644 index 00000000..3fb04a00 --- /dev/null +++ b/rubbos/app/httpd-2.0.64/docs/manual/stopping.html.en @@ -0,0 +1,235 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>Stopping and Restarting - Apache HTTP Server</title> +<link href="./style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="./style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="./style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /> +<link href="./images/favicon.ico" rel="shortcut icon" /></head> +<body id="manual-page"><div id="page-header"> +<p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.0</p> +<img alt="" src="./images/feather.gif" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="./images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="./">Version 2.0</a></div><div id="page-content"><div id="preamble"><h1>Stopping and Restarting</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="./de/stopping.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | +<a href="./en/stopping.html" title="English"> en </a> | +<a href="./es/stopping.html" hreflang="es" rel="alternate" title="Español"> es </a> | +<a href="./ja/stopping.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | +<a href="./ko/stopping.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | +<a href="./ru/stopping.html" hreflang="ru" rel="alternate" title="Russian"> ru </a> | +<a href="./tr/stopping.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> +</div> + + <p>This document covers stopping and restarting Apache on + Unix-like systems. Windows NT, 2000 and XP users should see + <a href="platform/windows.html#winsvc">Running Apache as a + Service</a> and Windows 9x and ME users should see <a href="platform/windows.html#wincons">Running Apache as a + Console Application</a> for information on how to control + Apache on those platforms.</p> +</div> +<div id="quickview"><ul id="toc"><li><img alt="" src="./images/down.gif" /> <a href="#introduction">Introduction</a></li> +<li><img alt="" src="./images/down.gif" /> <a href="#term">Stop Now</a></li> +<li><img alt="" src="./images/down.gif" /> <a href="#graceful">Graceful Restart</a></li> +<li><img alt="" src="./images/down.gif" /> <a href="#hup">Restart Now</a></li> +<li><img alt="" src="./images/down.gif" /> <a href="#race">Appendix: signals and race conditions</a></li> +</ul><h3>See also</h3><ul class="seealso"><li><code class="program"><a href="./programs/httpd.html">httpd</a></code></li><li><code class="program"><a href="./programs/apachectl.html">apachectl</a></code></li><li><a href="invoking.html">Starting</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> +<div class="section"> +<h2><a name="introduction" id="introduction">Introduction</a></h2> + + <p>In order to stop or restart Apache, you must send a signal to + the running <code class="program"><a href="./programs/httpd.html">httpd</a></code> processes. There are two ways to + send the signals. First, you can use the unix <code>kill</code> + command to directly send signals to the processes. You will + notice many <code class="program"><a href="./programs/httpd.html">httpd</a></code> executables running on your system, + but you should not send signals to any of them except the parent, + whose pid is in the <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code>. 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><a href="#term">TERM</a></code>, + <code><a href="#hup">HUP</a></code>, and + <code><a href="#graceful">USR1</a></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> + +<div class="example"><p><code>kill -TERM `cat /usr/local/apache2/logs/httpd.pid`</code></p></div> + + <p>The second method of signaling the <code class="program"><a href="./programs/httpd.html">httpd</a></code> processes + is to use the <code>-k</code> command line options: <code>stop</code>, + <code>restart</code>, and <code>graceful</code>, + as described below. These are arguments to the <code class="program"><a href="./programs/httpd.html">httpd</a></code> binary, but we recommend that + you send them using the <code class="program"><a href="./programs/apachectl.html">apachectl</a></code> control script, which + will pass them through to <code class="program"><a href="./programs/httpd.html">httpd</a></code>.</p> + + <p>After you have signaled <code class="program"><a href="./programs/httpd.html">httpd</a></code>, you can read about + its progress by issuing:</p> + +<div class="example"><p><code>tail -f /usr/local/apache2/logs/error_log</code></p></div> + + <p>Modify those examples to match your <code class="directive"><a href="./mod/core.html#serverroot">ServerRoot</a></code> and <code class="directive"><a href="./mod/mpm_common.html#pidfile">PidFile</a></code> settings.</p> +</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> +<div class="section"> +<h2><a name="term" id="term">Stop Now</a></h2> + +<dl><dt>Signal: TERM</dt> +<dd><code>apachectl -k stop</code></dd> +</dl> + + <p>Sending the <code>TERM</code> or <code>stop</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> +</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> +<div class="section"> +<h2><a name="graceful" id="graceful">Graceful Restart</a></h2> + +<dl><dt>Signal: USR1</dt> +<dd><code>apachectl -k graceful</code></dd> +</dl> + + <p>The <code>USR1</code> or <code>graceful</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> + + <div class="note">On certain platforms that do not allow <code>USR1</code> to + be used for a graceful restart, an alternative signal may be used (such + as <code>WINCH</code>). The command <code>apachectl graceful</code> + will send the right signal for your platform.</div> + + <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 + <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code> in the + following manner: if after one second at least <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code> 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 + <code class="directive"><a href="./mod/mpm_common.html#startservers">StartServers</a></code> + parameter.</p> + + <p>Users of <code class="module"><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 + 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> + + <div class="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 <code class="program"><a href="./programs/httpd.html">httpd</a></code>). 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 <code class="program"><a href="./programs/httpd.html">httpd</a></code> 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 + <code class="program"><a href="./programs/httpd.html">httpd</a></code> 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.</div> +</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> +<div class="section"> +<h2><a name="hup" id="hup">Restart Now</a></h2> + +<dl><dt>Signal: HUP</dt> +<dd><code>apachectl -k restart</code></dd> +</dl> + + <p>Sending the <code>HUP</code> or <code>restart</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 <code class="module"><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> + +<div class="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.</div> +</div><div class="top"><a href="#page-header"><img alt="top" src="./images/up.gif" /></a></div> +<div class="section"> +<h2><a name="race" id="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 simply put, + a race condition is a time-sensitive problem - if something happens + at just the wrong time or things happen in the wrong order, + undesired behaviour will result. If the same thing happens at the right + time, all will be well). For those architectures that have the "right" + feature set we have eliminated as many as we can. But it should + be noted that race conditions do still exist on certain + architectures.</p> + + <p>Architectures that use an on-disk <code class="directive"><a href="./mod/mpm_common.html#scoreboardfile">ScoreBoardFile</a></code> can potentially have + their scoreboards corrupted. 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 may 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 <code class="directive"><a href="./mod/mpm_common.html#scoreboardfile">ScoreBoardFile</a></code> documentation for + architecture which 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> +</div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="./de/stopping.html" hreflang="de" rel="alternate" title="Deutsch"> de </a> | +<a href="./en/stopping.html" title="English"> en </a> | +<a href="./es/stopping.html" hreflang="es" rel="alternate" title="Español"> es </a> | +<a href="./ja/stopping.html" hreflang="ja" rel="alternate" title="Japanese"> ja </a> | +<a href="./ko/stopping.html" hreflang="ko" rel="alternate" title="Korean"> ko </a> | +<a href="./ru/stopping.html" hreflang="ru" rel="alternate" title="Russian"> ru </a> | +<a href="./tr/stopping.html" hreflang="tr" rel="alternate" title="Türkçe"> tr </a></p> +</div><div id="footer"> +<p class="apache">Copyright 2009 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="./mod/">Modules</a> | <a href="./mod/directives.html">Directives</a> | <a href="./faq/">FAQ</a> | <a href="./glossary.html">Glossary</a> | <a href="./sitemap.html">Sitemap</a></p></div> +</body></html>
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