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<html lang="en"><head><META http-equiv="Content-Type" content="text/html; charset=UTF-8"><link href="../images/docs-stylesheet.css" rel="stylesheet" type="text/css"><title>Apache Tomcat 8 Configuration Reference (8.5.78) - The Cluster Receiver object</title><meta name="author" content="Filip Hanik"></head><body><div id="wrapper"><header><div id="header"><div><div><div class="logo noPrint"><a href="https://tomcat.apache.org/"><img alt="Tomcat Home" src="../images/tomcat.png"></a></div><div style="height: 1px;"></div><div class="asfLogo noPrint"><a href="https://www.apache.org/" target="_blank"><img src="../images/asf-logo.svg" alt="The Apache Software Foundation" style="width: 266px; height: 83px;"></a></div><h1>Apache Tomcat 8 Configuration Reference</h1><div class="versionInfo">
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Version 8.5.78,
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<time datetime="2022-03-31">Mar 31 2022</time></div><div style="height: 1px;"></div><div style="clear: left;"></div></div></div></div></header><div id="middle"><div><div id="mainLeft" class="noprint"><div><nav><div><h2>Links</h2><ul><li><a href="../index.html">Docs Home</a></li><li><a href="index.html">Config Ref. Home</a></li><li><a href="https://wiki.apache.org/tomcat/FAQ">FAQ</a></li><li><a href="#comments_section">User Comments</a></li></ul></div><div><h2>Top Level Elements</h2><ul><li><a href="server.html">Server</a></li><li><a href="service.html">Service</a></li></ul></div><div><h2>Executors</h2><ul><li><a href="executor.html">Executor</a></li></ul></div><div><h2>Connectors</h2><ul><li><a href="http.html">HTTP/1.1</a></li><li><a href="http2.html">HTTP/2</a></li><li><a href="ajp.html">AJP</a></li></ul></div><div><h2>Containers</h2><ul><li><a href="context.html">Context</a></li><li><a href="engine.html">Engine</a></li><li><a href="host.html">Host</a></li><li><a href="cluster.html">Cluster</a></li></ul></div><div><h2>Nested Components</h2><ul><li><a href="cookie-processor.html">CookieProcessor</a></li><li><a href="credentialhandler.html">CredentialHandler</a></li><li><a href="globalresources.html">Global Resources</a></li><li><a href="jar-scanner.html">JarScanner</a></li><li><a href="jar-scan-filter.html">JarScanFilter</a></li><li><a href="listeners.html">Listeners</a></li><li><a href="loader.html">Loader</a></li><li><a href="manager.html">Manager</a></li><li><a href="realm.html">Realm</a></li><li><a href="resources.html">Resources</a></li><li><a href="sessionidgenerator.html">SessionIdGenerator</a></li><li><a href="valve.html">Valve</a></li></ul></div><div><h2>Cluster Elements</h2><ul><li><a href="cluster.html">Cluster</a></li><li><a href="cluster-manager.html">Manager</a></li><li><a href="cluster-channel.html">Channel</a></li><li><a href="cluster-membership.html">Channel/Membership</a></li><li><a href="cluster-sender.html">Channel/Sender</a></li><li><a href="cluster-receiver.html">Channel/Receiver</a></li><li><a href="cluster-interceptor.html">Channel/Interceptor</a></li><li><a href="cluster-valve.html">Valve</a></li><li><a href="cluster-deployer.html">Deployer</a></li><li><a href="cluster-listener.html">ClusterListener</a></li></ul></div><div><h2>web.xml</h2><ul><li><a href="filter.html">Filter</a></li></ul></div><div><h2>Other</h2><ul><li><a href="systemprops.html">System properties</a></li><li><a href="jaspic.html">JASPIC</a></li></ul></div></nav></div></div><div id="mainRight"><div id="content"><h2>The Cluster Receiver object</h2><h3 id="Table_of_Contents">Table of Contents</h3><div class="text">
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<ul><li><a href="#Introduction">Introduction</a></li><li><a href="#Blocking_vs_Non-Blocking_Receiver">Blocking vs Non-Blocking Receiver</a></li><li><a href="#Attributes">Attributes</a><ol><li><a href="#Common_Attributes">Common Attributes</a></li><li><a href="#NioReceiver">NioReceiver</a></li><li><a href="#BioReceiver">BioReceiver</a></li></ol></li></ul>
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</div><h3 id="Introduction">Introduction</h3><div class="text">
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<p>
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The receiver component is responsible for receiving cluster messages.
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As you might notice through the configuration, is that the receiving of messages
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and sending of messages are two different components, this is different from many other
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frameworks, but there is a good reason for it, to decouple the logic for how messages are sent from
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how messages are received.<br>
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The receiver is very much like the Tomcat Connector, its the base of the thread pool
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for incoming cluster messages. The receiver is straight forward, but all the socket settings
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for incoming traffic are managed here.
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</p>
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</div><h3 id="Blocking_vs_Non-Blocking_Receiver">Blocking vs Non-Blocking Receiver</h3><div class="text">
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<p>
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The receiver supports both a non blocking, <code>org.apache.catalina.tribes.transport.nio.NioReceiver</code>, and a
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blocking, <code>org.apache.catalina.tribes.transport.bio.BioReceiver</code>. It is preferred to use the non blocking receiver
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to be able to grow your cluster without running into thread starvation.<br>
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Using the non blocking receiver allows you to with a very limited thread count to serve a large number of messages.
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Usually the rule is to use 1 thread per node in the cluster for small clusters, and then depending on your message frequency
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and your hardware, you'll find an optimal number of threads peak out at a certain number.
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</p>
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</div><h3 id="Attributes">Attributes</h3><div class="text">
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<div class="subsection"><h4 id="Common_Attributes">Common Attributes</h4><div class="text">
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<table class="defaultTable"><tr><th style="width: 15%;">
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Attribute
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</th><th style="width: 85%;">
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Description
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</th></tr><tr><td><strong><code class="attributeName">className</code></strong></td><td>
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The implementation of the receiver component. Two implementations available,
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<code>org.apache.catalina.tribes.transport.nio.NioReceiver</code> and
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<code>org.apache.catalina.tribes.transport.bio.BioReceiver</code>.<br>
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The <code>org.apache.catalina.tribes.transport.nio.NioReceiver</code> is the
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preferred implementation
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</td></tr><tr><td><code class="attributeName">address</code></td><td>
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The address (network interface) to listen for incoming traffic.
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Same as the bind address. The default value is <code>auto</code> and translates to
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<code>java.net.InetAddress.getLocalHost().getHostAddress()</code>.
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</td></tr><tr><td><code class="attributeName">direct</code></td><td>
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Possible values are <code>true</code> or <code>false</code>.
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Set to true if you want the receiver to use direct bytebuffers when reading data
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from the sockets.
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</td></tr><tr><td><code class="attributeName">port</code></td><td>
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The listen port for incoming data. The default value is <code>4000</code>.
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To avoid port conflicts the receiver will automatically bind to a free port within the range of
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<code> port <= bindPort < port+autoBind</code>
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So for example, if port is 4000, and autoBind is set to 10, then the receiver will open up
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a server socket on the first available port in the range 4000-4009.
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</td></tr><tr><td><code class="attributeName">autoBind</code></td><td>
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Default value is <code>100</code>.
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Use this value if you wish to automatically avoid port conflicts the cluster receiver will try to open a
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server socket on the <code>port</code> attribute port, and then work up <code>autoBind</code> number of times.
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</td></tr><tr><td><code class="attributeName">securePort</code></td><td>
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The secure listen port. This port is SSL enabled. If this attribute is omitted no SSL port is opened up.
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There default value is unset, meaning there is no SSL socket available.
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</td></tr><tr><td><code class="attributeName">udpPort</code></td><td>
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The UDP listen port. If this attribute is omitted no UDP port is opened up.
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There default value is unset, meaning there is no UDP listener available.
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</td></tr><tr><td><code class="attributeName">selectorTimeout</code></td><td>
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The value in milliseconds for the polling timeout in the <code>NioReceiver</code>. On older versions of the JDK
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there have been bugs, that should all now be cleared out where the selector never woke up.
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The default value is a very high <code>5000</code> milliseconds.
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</td></tr><tr><td><code class="attributeName">maxThreads</code></td><td>
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The maximum number of threads in the receiver thread pool. The default value is <code>15</code>
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Adjust this value relative to the number of nodes in the cluster, the number of messages being exchanged and
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the hardware you are running on. A higher value doesn't mean more efficiency, tune this value according to your
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own test results.
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</td></tr><tr><td><code class="attributeName">minThreads</code></td><td>
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Minimum number of threads to be created when the receiver is started up. Default value is <code>6</code>
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</td></tr><tr><td><code class="attributeName">maxIdleTime</code></td><td>
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Maximum number of milliseconds of until Idle thread terminates. Default value is <code>60000</code> milliseconds.
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</td></tr><tr><td><code class="attributeName">ooBInline</code></td><td>
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Boolean value for the socket OOBINLINE option. Possible values are <code>true</code> or <code>false</code>.
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</td></tr><tr><td><code class="attributeName">rxBufSize</code></td><td>
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The receiver buffer size on the receiving sockets. Value is in bytes, the default value is <code>43800</code> bytes.
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</td></tr><tr><td><code class="attributeName">txBufSize</code></td><td>
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The sending buffer size on the receiving sockets. Value is in bytes, the default value is <code>25188</code> bytes.
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</td></tr><tr><td><code class="attributeName">udpRxBufSize</code></td><td>
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The receive buffer size on the datagram socket.
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Default value is <code>25188</code> bytes.
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</td></tr><tr><td><code class="attributeName">udpTxBufSize</code></td><td>
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The send buffer size on the datagram socket.
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Default value is <code>43800</code> bytes.
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</td></tr><tr><td><code class="attributeName">soKeepAlive</code></td><td>
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Boolean value for the socket SO_KEEPALIVE option. Possible values are <code>true</code> or <code>false</code>.
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</td></tr><tr><td><code class="attributeName">soLingerOn</code></td><td>
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Boolean value to determine whether to use the SO_LINGER socket option.
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Possible values are <code>true</code> or <code>false</code>. Default value is <code>true</code>.
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</td></tr><tr><td><code class="attributeName">soLingerTime</code></td><td>
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Sets the SO_LINGER socket option time value. The value is in seconds.
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The default value is <code>3</code> seconds.
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</td></tr><tr><td><code class="attributeName">soReuseAddress</code></td><td>
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Boolean value for the socket SO_REUSEADDR option. Possible values are <code>true</code> or <code>false</code>.
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</td></tr><tr><td><code class="attributeName">tcpNoDelay</code></td><td>
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Boolean value for the socket TCP_NODELAY option. Possible values are <code>true</code> or <code>false</code>.
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The default value is <code>true</code>
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</td></tr><tr><td><code class="attributeName">timeout</code></td><td>
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Sets the SO_TIMEOUT option on the socket. The value is in milliseconds and the default value is <code>3000</code>
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milliseconds.
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</td></tr><tr><td><code class="attributeName">useBufferPool</code></td><td>
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Boolean value whether to use a shared buffer pool of cached <code>org.apache.catalina.tribes.io.XByteBuffer</code>
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objects. If set to true, the XByteBuffer that is used to pass a message up the channel, will be recycled at the end
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of the requests. This means that interceptors in the channel must not maintain a reference to the object
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after the <code>org.apache.catalina.tribes.ChannelInterceptor#messageReceived</code> method has exited.
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</td></tr></table>
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</div></div>
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<div class="subsection"><h4 id="NioReceiver">NioReceiver</h4><div class="text">
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</div></div>
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<div class="subsection"><h4 id="BioReceiver">BioReceiver</h4><div class="text">
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</div></div>
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