171 lines
7.3 KiB
XML
171 lines
7.3 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<!DOCTYPE document [
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<!ENTITY project SYSTEM "project.xml">
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]>
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<document url="cluster-membership.html">
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&project;
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<properties>
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<author email="fhanik@apache.org">Filip Hanik</author>
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<title>The Cluster Membership object</title>
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</properties>
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<body>
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<section name="Table of Contents">
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<toc/>
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</section>
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<section name="Introduction">
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<p>
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The membership component in the Apache Tribes <a href="cluster-channel.html">Channel</a> is responsible
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for dynamic discovery of other members(nodes) in the cluster.
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</p>
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</section>
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<section name="Default Implementation">
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<p>
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The default implementation of the cluster group notification is built on top of multicast heartbeats
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sent using UDP packets to a multicast IP address.
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Cluster members are grouped together by using the same multicast address/port combination.
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Each member sends out a heartbeat with a given interval (<code>frequency</code>), and this
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heartbeat is used for dynamic discovery.
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In a similar fashion, if a heartbeat has not been received in a timeframe specified by <code>dropTime</code>
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ms. a member is considered suspect and the channel and any membership listener will be notified.
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</p>
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</section>
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<section name="Attributes">
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<subsection name="Multicast Attributes">
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<attributes>
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<attribute name="className" required="true">
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<p>
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The default value is <code>org.apache.catalina.tribes.membership.McastService</code>
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and is currently the only implementation.
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This implementation uses multicast heartbeats for member discovery.
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</p>
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</attribute>
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<attribute name="address" required="false">
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<p>
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The multicast address that the membership will broadcast its presence and listen
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for other heartbeats on. The default value is <code>228.0.0.4</code>
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Make sure your network is enabled for multicast traffic.<br/>
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The multicast address, in conjunction with the <code>port</code> is what
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creates a cluster group. To divide up your farm into several different group, or to
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split up QA from production, change the <code>port</code> or the <code>address</code>
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<br/>Previously known as mcastAddr.
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</p>
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</attribute>
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<attribute name="port" required="false">
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<p>
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The multicast port, the default value is <code>45564</code><br/>
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The multicast port, in conjunction with the <code>address</code> is what
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creates a cluster group. To divide up your farm into several different group, or to
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split up QA from production, change the <code>port</code> or the <code>address</code>
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</p>
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</attribute>
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<attribute name="frequency" required="false">
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<p>
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The frequency in milliseconds in which heartbeats are sent out. The default value is <code>500</code> ms.<br/>
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In most cases the default value is sufficient. Changing this value, simply changes the interval in between heartbeats.
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</p>
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</attribute>
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<attribute name="dropTime" required="false">
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<p>
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The membership component will time out members and notify the Channel if a member fails to send a heartbeat within
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a give time. The default value is <code>3000</code> ms. This means, that if a heartbeat is not received from a
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member in that timeframe, the membership component will notify the cluster of this.<br/>
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On a high latency network you may wish to increase this value, to protect against false positives.<br/>
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Apache Tribes also provides a <a href="cluster-interceptor.html#org.apache.catalina.tribes.group.interceptors.TcpFailureDetector_Attributes"><code>TcpFailureDetector</code></a> that will
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verify a timeout using a TCP connection when a heartbeat timeout has occurred. This protects against false positives.
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</p>
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</attribute>
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<attribute name="bind" required="false">
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<p>
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Use this attribute if you wish to bind your multicast traffic to a specific network interface.
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By default, or when this attribute is unset, it tries to bind to <code>0.0.0.0</code> and sometimes on multihomed hosts
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this becomes a problem.
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</p>
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</attribute>
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<attribute name="ttl" required="false">
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<p>
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The time-to-live setting for the multicast heartbeats.
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This setting should be a value between 0 and 255. The default value is VM implementation specific.
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</p>
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</attribute>
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<attribute name="domain" required="false">
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<p>
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Apache Tribes has the ability to logically group members into domains, by using this domain attribute.
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The <code>org.apache.catalina.tribes.Member.getDomain()</code> method returns the value specified here.
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</p>
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</attribute>
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<attribute name="soTimeout" required="false">
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<p>
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The sending and receiving of heartbeats is done on a single thread, hence to avoid blocking this thread forever,
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you can control the <code>SO_TIMEOUT</code> value on this socket.<br/>
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If a value smaller or equal to 0 is presented, the code will default this value to frequency
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</p>
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</attribute>
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<attribute name="recoveryEnabled" required="false">
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<p>
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In case of a network failure, Java multicast socket don't transparently fail over, instead the socket will continuously
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throw IOException upon each receive request. When recoveryEnabled is set to true, this will close the multicast socket
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and open a new socket with the same properties as defined above.<br/>
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The default is <code>true</code>. <br/>
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</p>
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</attribute>
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<attribute name="recoveryCounter" required="false">
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<p>
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When <code>recoveryEnabled==true</code> this value indicates how many
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times an error has to occur before recovery is attempted. The default is
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<code>10</code>. <br/>
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</p>
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</attribute>
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<attribute name="recoverySleepTime" required="false">
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<p>
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When <code>recoveryEnabled==true</code> this value indicates how long time (in milliseconds)
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the system will sleep in between recovery attempts, until it recovers successfully.
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The default is <code>5000</code> (5 seconds). <br/>
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</p>
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</attribute>
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<attribute name="localLoopbackDisabled" required="false">
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<p>
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Membership uses multicast, it will call <code>java.net.MulticastSocket.setLoopbackMode(localLoopbackDisabled)</code>.
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When <code>localLoopbackDisabled==true</code> multicast messages will not reach other nodes on the same local machine.
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The default is <code>false</code>. <br/>
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</p>
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</attribute>
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</attributes>
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</subsection>
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</section>
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</body>
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</document>
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