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<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Apache Tomcat 7 Configuration Reference (7.0.108) - The Cluster object</title><meta name="author" content="Filip Hanik"><style type="text/css" media="print">
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</style></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="https://tomcat.apache.org/"><img src="../images/tomcat.gif" align="right" alt="
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The Apache Tomcat Servlet/JSP Container
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" border="0"></a></td><td><h1><font face="arial,helvetica,sanserif">Apache Tomcat 7</font></h1><font face="arial,helvetica,sanserif">Version 7.0.108, Jan 28 2021</font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="../images/asf-logo.svg" align="right" alt="Apache Logo" border="0" style="width: 266px;height: 83px;"></a></td></tr></table><table border="0" width="100%" cellspacing="4"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><tr><!--LEFT SIDE NAVIGATION--><td width="20%" valign="top" nowrap class="noPrint"><p><strong>Links</strong></p><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><p><strong>Top Level Elements</strong></p><ul><li><a href="server.html">Server</a></li><li><a href="service.html">Service</a></li></ul><p><strong>Executors</strong></p><ul><li><a href="executor.html">Executor</a></li></ul><p><strong>Connectors</strong></p><ul><li><a href="http.html">HTTP</a></li><li><a href="ajp.html">AJP</a></li></ul><p><strong>Containers</strong></p><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><p><strong>Nested Components</strong></p><ul><li><a href="globalresources.html">Global Resources</a></li><li><a href="jar-scanner.html">JarScanner</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><p><strong>Cluster Elements</strong></p><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><p><strong>web.xml</strong></p><ul><li><a href="filter.html">Filter</a></li></ul><p><strong>Other</strong></p><ul><li><a href="systemprops.html">System properties</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left" id="mainBody"><h1>The Cluster object</h1><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Table of Contents"><!--()--></a><a name="Table_of_Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote>
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<ul><li><a href="#Introduction">Introduction</a></li><li><a href="#Security">Security</a></li><li><a href="#Engine_vs_Host_placement">Engine vs Host placement</a></li><li><a href="#Context_Attribute_Replication">Context Attribute Replication</a></li><li><a href="#Nested_Components">Nested Components</a></li><li><a href="#Deprecated_configuration_options">Deprecated configuration options</a></li><li><a href="#Attributes">Attributes</a><ol><li><a href="#SimpleTcpCluster_Attributes">SimpleTcpCluster Attributes</a></li></ol></li></ul>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote>
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<p>
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The tomcat cluster implementation provides session replication, context attribute replication and
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cluster wide WAR file deployment.
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While the <code>Cluster</code> configuration is fairly complex, the default configuration will work
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for most people out of the box. </p><p>
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The Tomcat Cluster implementation is very extensible, and hence we have exposed a myriad of options,
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making the configuration seem like a lot, but don't lose faith, instead you have a tremendous control
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over what is going on.</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Security"><strong>Security</strong></a></font></td></tr><tr><td><blockquote>
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<p>The cluster implementation is written on the basis that a secure, trusted
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network is used for all of the cluster related network traffic. It is not safe
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to run a cluster on a insecure, untrusted network.</p>
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<p>There are many options for providing a secure, trusted network for use by a
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Tomcat cluster. These include:</p>
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<ul>
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<li><a href="cluster-interceptor.html#org.apache.catalina.tribes.group.interceptors.EncryptInterceptor_Attributes">EncryptInterceptor</a></li>
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<li>private LAN</li>
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<li>a Virtual Private Network (VPN)</li>
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<li>IPSEC</li>
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</ul>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Engine vs Host placement"><!--()--></a><a name="Engine_vs_Host_placement"><strong>Engine vs Host placement</strong></a></font></td></tr><tr><td><blockquote>
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<p>
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You can place the <code><Cluster></code> element inside either the <code><Engine></code>
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container or the <code><Host></code> container.<br>
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Placing it in the engine, means that you will support clustering in all virtual hosts of Tomcat,
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and share the messaging component. When you place the <code><Cluster></code> inside the <code><Engine></code>
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element, the cluster will append the host name of each session manager to the managers name so that two contexts with
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the same name but sitting inside two different hosts will be distinguishable.
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</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Context Attribute Replication"><!--()--></a><a name="Context_Attribute_Replication"><strong>Context Attribute Replication</strong></a></font></td></tr><tr><td><blockquote>
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<p>To configure context attribute replication, simply do this by swapping out the context implementation
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used for your application context.</p>
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<div class="codeBox"><pre><code><Context className="org.apache.catalina.ha.context.ReplicatedContext"/></code></pre></div>
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<p>
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This context extends the Tomcat <code><a href="context.html">StandardContext</a></code>
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so all the options from the <a href="context.html">base implementation</a> are valid.
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</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Nested Components"><!--()--></a><a name="Nested_Components"><strong>Nested Components</strong></a></font></td></tr><tr><td><blockquote>
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<p><b><a href="cluster-manager.html">Manager</a>:</b> <br>
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The session manager element identifies what kind of session manager is used in this cluster implementation.
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This manager configuration is identical to the one you would use in a regular <code><a href="context.html#Nested_Components"><Context></a></code> configuration.
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<br>The default value is the <code>org.apache.catalina.ha.session.DeltaManager</code> that is closely coupled with
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the <code>SimpleTcpCluster</code> implementation. Other managers like the <code>org.apache.catalina.ha.session.BackupManager</code>
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are/could be loosely coupled and don't rely on the <code>SimpleTcpCluster</code> for its data replication.
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</p>
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<p><b><a href="cluster-channel.html">Channel</a>:</b> <br>
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The Channel and its sub components are all part of the IO layer
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for the cluster group, and is a module in it's own that we have nick named "Tribes"
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<br>
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Any configuring and tuning of the network layer, the messaging and the membership logic
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will be done in the channel and its nested components.
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You can always find out more about <a href="../tribes/introduction.html">Apache Tribes</a>
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</p>
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<p><b><a href="cluster-valve.html">Valve</a>:</b> <br>
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The Tomcat Cluster implementation uses <code>Tomcat <a href="valve.html">Valves</a></code> to
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track when requests enter and exit the servlet container. It uses these valves to be able to make
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intelligent decisions on when to replicate data, which is always at the end of a request.
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</p>
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<p><b><a href="cluster-deployer.html">Deployer</a>:</b> <br>
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The Deployer component is the Tomcat Farm Deployer. It allows you to deploy and undeploy applications
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cluster wide.
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</p>
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<p><b><a href="cluster-listener.html">ClusterListener</a>:</b> <br>
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ClusterListener's are used to track messages sent and received using the <code>SimpleTcpCluster</code>.
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If you wish to track messages, you can add a listener here, or you can add a valve to the channel object.
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</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Deprecated configuration options"><!--()--></a><a name="Deprecated_configuration_options"><strong>Deprecated configuration options</strong></a></font></td></tr><tr><td><blockquote>
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<p>
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<b>Deprecated settings:</b> In the previous version of Tomcat you were able to control session
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manager settings using manager.<property>=value.
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This has been discontinued, as the way it was written interferes with
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the ability to support multiple different manager classes under one cluster implementation,
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as the same properties might have the different effect on different managers.
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</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Attributes"><strong>Attributes</strong></a></font></td></tr><tr><td><blockquote>
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<table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#828DA6"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="SimpleTcpCluster Attributes"><!--()--></a><a name="SimpleTcpCluster_Attributes"><strong>SimpleTcpCluster Attributes</strong></a></font></td></tr><tr><td><blockquote>
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<table border="1" cellpadding="5"><tr><th width="15%" bgcolor="#023264"><font color="#ffffff">Attribute</font></th><th width="85%" bgcolor="#023264"><font color="#ffffff">Description</font></th></tr><tr><td align="left" valign="center"><strong><code class="attributeName">className</code></strong></td><td align="left" valign="center">
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<p>The main cluster class, currently only one is available,
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<code>org.apache.catalina.ha.tcp.SimpleTcpCluster</code>
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</p>
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</td></tr><tr><td align="left" valign="center"><strong><code class="attributeName">channelSendOptions</code></strong></td><td align="left" valign="center">
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<p>The Tribes channel send options, default is <code>8</code>.<br>
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This option is used to set the flag that all messages sent through the
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SimpleTcpCluster uses. The flag decides how the messages are sent, and is a simple logical OR.</p>
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<div class="codeBox"><pre><code>int options = Channel.SEND_OPTIONS_ASYNCHRONOUS |
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Channel.SEND_OPTIONS_SYNCHRONIZED_ACK |
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Channel.SEND_OPTIONS_USE_ACK;</code></pre></div>
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<p>Some of the values are:<br>
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<code>Channel.SEND_OPTIONS_SYNCHRONIZED_ACK = 0x0004</code><br>
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<code>Channel.SEND_OPTIONS_ASYNCHRONOUS = 0x0008</code><br>
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<code>Channel.SEND_OPTIONS_USE_ACK = 0x0002</code><br>
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So to use ACK and ASYNC messaging, the flag would be <code>10</code> (8+2)
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<br>
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Note that if you use ASYNC messaging it is possible for update messages
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for a session to be processed by the receiving nodes in a different order
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to the order in which they were sent.</p>
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</td></tr><tr><td align="left" valign="center"><code class="attributeName">channelStartOptions</code></td><td align="left" valign="center">
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<p>Sets the start and stop flags for the <Channel> object used by the cluster.
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The default is <code>Channel.DEFAULT</code> which starts all the channel services, such as
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sender, receiver, multicast sender and multicast receiver.
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The following flags are available today:</p>
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<div class="codeBox"><pre><code>Channel.DEFAULT = Channel.SND_RX_SEQ (1) |
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Channel.SND_TX_SEQ (2) |
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Channel.MBR_RX_SEQ (4) |
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Channel.MBR_TX_SEQ (8);</code></pre></div>
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<p>To start a channel without multicasting, you would want to use the value <code>Channel.SND_RX_SEQ | Channel.SND_TX_SEQ</code>
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that equals to <code>3</code>.
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</p>
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</td></tr><tr><td align="left" valign="center"><code class="attributeName">heartbeatBackgroundEnabled</code></td><td align="left" valign="center">
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<p>Flag whether invoke channel heartbeat at container background thread. Default value is false.
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Enable this flag don't forget to disable the channel heartbeat thread.
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</p>
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</td></tr><tr><td align="left" valign="center"><code class="attributeName">notifyLifecycleListenerOnFailure</code></td><td align="left" valign="center">
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<p>Flag whether notify LifecycleListeners if all ClusterListener couldn't accept channel message.
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Default value is false.
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</p>
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</td></tr></table>
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</blockquote></td></tr></table>
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</blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em>
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Copyright © 1999-2021, Apache Software Foundation
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</em></font></div></td></tr></table></body></html> |