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| Version: 9.3.28.v20191105</span></td><td style="width: 50%"></td></tr></table><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Limiting Load</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="high-load.html"><i class="fa fa-chevron-left" aria-hidden="true"></i> Previous</a> </td><th width="60%" align="center">Chapter 20. Optimizing Jetty<br><a accesskey="p" href="index.html"><i class="fa fa-home" aria-hidden="true"></i> Home</a></th><td width="20%" align="right"> <a accesskey="n" href="jetty-dev-guide.html">Next <i class="fa fa-chevron-right" aria-hidden="true"></i></a></td></tr></table><hr></div><div xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times" class="jetty-callout"><h5 class="callout"><a href="http://www.webtide.com/">Contact the core Jetty developers at |
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| </p></div><div class="section"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="limit-load"></a>Limiting Load</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="section"><a href="limit-load.html#_low_resources_monitor">Low Resources Monitor</a></span></dt></dl></div><p>To achieve optimal fair handling for all users of a server, it can be necessary to limit the resources that each user/connection can utilize so as to maximize throughput for the server or to ensure that the entire server runs within the limitations of it’s runtime.</p><div class="section"><div class="titlepage"><div><div><h3 class="title"><a name="_low_resources_monitor"></a>Low Resources Monitor</h3></div></div></div><p>An instance of <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/server/LowResourcesMonitor.html" target="_top">LowResourcesMonitor</a> may be added to a Jetty server to monitor for low resources situations and to take action to limit the number of idle connections on the server. |
| To configure the low resources monitor, you can enable the the <code class="literal">lowresources.mod</code> on the command line, which has the effect of including the following XML configuration:</p><pre xmlns:jfetch="java:org.eclipse.jetty.xslt.tools.JavaSourceFetchExtension" xmlns:fetch="java:org.eclipse.jetty.xslt.tools.SourceFetchExtension" xmlns:d="http://docbook.org/ns/docbook" xmlns:l="http://docbook.sourceforge.net/xmlns/l10n/1.0" xmlns:xslthl="http://xslthl.sf.net" xmlns:gcse="http://www.google.com" xmlns:date="http://exslt.org/dates-and-times"><code><?xml version="1.0"?> |
| <!DOCTYPE Configure PUBLIC "-//Jetty//Configure//EN" "http://www.eclipse.org/jetty/configure_9_3.dtd"> |
| |
| <!-- =============================================================== --> |
| <!-- Mixin the Low Resources Monitor --> |
| <!-- =============================================================== --> |
| |
| <Configure id="Server" class="org.eclipse.jetty.server.Server"> |
| <Call name="addBean"> |
| <Arg> |
| <New class="org.eclipse.jetty.server.LowResourceMonitor"> |
| <Arg name="server"><Ref refid='Server'/></Arg> |
| <Set name="period"><Property name="jetty.lowresources.period" deprecated="lowresources.period" default="1000"/></Set> |
| <Set name="lowResourcesIdleTimeout"><Property name="jetty.lowresources.idleTimeout" deprecated="lowresources.lowResourcesIdleTimeout" default="1000"/></Set> |
| <Set name="monitorThreads"><Property name="jetty.lowresources.monitorThreads" deprecated="lowresources.monitorThreads" default="true"/></Set> |
| <Set name="maxConnections"><Property name="jetty.lowresources.maxConnections" deprecated="lowresources.maxConnections" default="0"/></Set> |
| <Set name="maxMemory"><Property name="jetty.lowresources.maxMemory" deprecated="lowresources.maxMemory" default="0"/></Set> |
| <Set name="maxLowResourcesTime"><Property name="jetty.lowresources.maxLowResourcesTime" deprecated="lowresources.maxLowResourcesTime" default="5000"/></Set> |
| </New> |
| </Arg> |
| </Call> |
| </Configure></code></pre><p>The monitor is configured with a period in milliseconds at which it will scan the server looking for a low resources condition, which may be one of:</p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem">If <code class="literal">monitorThreads</code> is configured as true and a connectors Executor is an instance of <a class="link" href="http://www.eclipse.org/jetty/javadoc/9.3.28.v20191105/org/eclipse/jetty/util/thread/ThreadPool.html" target="_top">ThreadPool</a>, then its <code class="literal">isLowOnThreads()</code> method is used to detect low resources.</li><li class="listitem">If <code class="literal">maxConnections</code> is configured to a number >0 then if the total number of connections from all monitored connectors exceeds this value, then low resources state is entered.</li><li class="listitem">If the <code class="literal">maxMemory</code> field is configured to a number of bytes >0 then if the JVMs total memory minus its idle memory exceeds this value, then low resources state is entered.</li></ul></div><p>Once low resources state is detected, then the monitor will iterate over all existing connections and set their <code class="literal">IdleTimeout</code> to its configured <code class="literal">lowResourcesIdleTimeout</code> in milliseconds. |
| This allows the idle time of existing connections to be reduced so that the connection is quickly closed if no further request are received.</p><p>If the low resources state persists longer than the time in milliseconds configured for the <code class="literal">maxLowResourcesTime</code> field, the the <code class="literal">lowResourcesIdleTimeout</code> is repeatedly applied so that new connections as well as existing connections will be limited.</p></div></div><script type="text/javascript"> |
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