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| <!DOCTYPE document [ |
| <!ENTITY project SYSTEM "project.xml"> |
| ]> |
| <document url="cluster-membership.html"> |
| |
| &project; |
| |
| <properties> |
| <author email="fhanik@apache.org">Filip Hanik</author> |
| <title>The Cluster Membership object</title> |
| </properties> |
| |
| <body> |
| |
| <section name="Table of Contents"> |
| <toc/> |
| </section> |
| |
| <section name="Introduction"> |
| <p> |
| The membership component in the Apache Tribes <a href="cluster-channel.html">Channel</a> is responsible |
| for dynamic discovery of other members(nodes) in the cluster. |
| </p> |
| </section> |
| |
| <section name="Default Implementation"> |
| <p> |
| The default implementation of the cluster group notification is built on top of multicast heartbeats |
| sent using UDP packets to a multicast IP address. |
| Cluster members are grouped together by using the same multicast address/port combination. |
| Each member sends out a heartbeat with a given interval (<code>frequency</code>), and this |
| heartbeat is used for dynamic discovery. |
| In a similar fashion, if a heartbeat has not been received in a timeframe specified by <code>dropTime</code> |
| ms. a member is considered suspect and the channel and any membership listener will be notified. |
| </p> |
| </section> |
| |
| |
| |
| <section name="Attributes"> |
| |
| <subsection name="Multicast Attributes"> |
| |
| <attributes> |
| |
| <attribute name="className" required="true"> |
| <p> |
| The default value is <code>org.apache.catalina.tribes.membership.McastService</code> |
| and is currently the only implementation. |
| This implementation uses multicast heartbeats for member discovery. |
| </p> |
| </attribute> |
| <attribute name="address" required="false"> |
| <p> |
| The multicast address that the membership will broadcast its presence and listen |
| for other heartbeats on. The default value is <code>228.0.0.4</code> |
| Make sure your network is enabled for multicast traffic.<br/> |
| The multicast address, in conjunction with the <code>port</code> is what |
| creates a cluster group. To divide up your farm into several different group, or to |
| split up QA from production, change the <code>port</code> or the <code>address</code> |
| <br/>Previously known as mcastAddr. |
| </p> |
| </attribute> |
| <attribute name="port" required="false"> |
| <p> |
| The multicast port, the default value is <code>45564</code><br/> |
| The multicast port, in conjunction with the <code>address</code> is what |
| creates a cluster group. To divide up your farm into several different group, or to |
| split up QA from production, change the <code>port</code> or the <code>address</code> |
| </p> |
| </attribute> |
| <attribute name="frequency" required="false"> |
| <p> |
| The frequency in milliseconds in which heartbeats are sent out. The default value is <code>500</code> ms.<br/> |
| In most cases the default value is sufficient. Changing this value, simply changes the interval in between heartbeats. |
| </p> |
| </attribute> |
| <attribute name="dropTime" required="false"> |
| <p> |
| The membership component will time out members and notify the Channel if a member fails to send a heartbeat within |
| a give time. The default value is <code>3000</code> ms. This means, that if a heartbeat is not received from a |
| member in that timeframe, the membership component will notify the cluster of this.<br/> |
| On a high latency network you may wish to increase this value, to protect against false positives.<br/> |
| Apache Tribes also provides a <a href="cluster-interceptor.html#org.apache.catalina.tribes.group.interceptors.TcpFailureDetector_Attributes"><code>TcpFailureDetector</code></a> that will |
| verify a timeout using a TCP connection when a heartbeat timeout has occurred. This protects against false positives. |
| </p> |
| </attribute> |
| <attribute name="bind" required="false"> |
| <p> |
| Use this attribute if you wish to bind your multicast traffic to a specific network interface. |
| By default, or when this attribute is unset, it tries to bind to <code>0.0.0.0</code> and sometimes on multihomed hosts |
| this becomes a problem. |
| </p> |
| </attribute> |
| <attribute name="ttl" required="false"> |
| <p> |
| The time-to-live setting for the multicast heartbeats. |
| This setting should be a value between 0 and 255. The default value is VM implementation specific. |
| </p> |
| </attribute> |
| <attribute name="domain" required="false"> |
| <p> |
| Apache Tribes has the ability to logically group members into domains, by using this domain attribute. |
| The <code>org.apache.catalina.tribes.Member.getDomain()</code> method returns the value specified here. |
| </p> |
| </attribute> |
| <attribute name="soTimeout" required="false"> |
| <p> |
| The sending and receiving of heartbeats is done on a single thread, hence to avoid blocking this thread forever, |
| you can control the <code>SO_TIMEOUT</code> value on this socket.<br/> |
| If a value smaller or equal to 0 is presented, the code will default this value to frequency |
| </p> |
| </attribute> |
| <attribute name="recoveryEnabled" required="false"> |
| <p> |
| In case of a network failure, Java multicast socket don't transparently fail over, instead the socket will continuously |
| throw IOException upon each receive request. When recoveryEnabled is set to true, this will close the multicast socket |
| and open a new socket with the same properties as defined above.<br/> |
| The default is <code>true</code>. <br/> |
| </p> |
| </attribute> |
| <attribute name="recoveryCounter" required="false"> |
| <p> |
| When <code>recoveryEnabled==true</code> this value indicates how many |
| times an error has to occur before recovery is attempted. The default is |
| <code>10</code>. <br/> |
| </p> |
| </attribute> |
| <attribute name="recoverySleepTime" required="false"> |
| <p> |
| When <code>recoveryEnabled==true</code> this value indicates how long time (in milliseconds) |
| the system will sleep in between recovery attempts, until it recovers successfully. |
| The default is <code>5000</code> (5 seconds). <br/> |
| </p> |
| </attribute> |
| |
| <attribute name="localLoopbackDisabled" required="false"> |
| <p> |
| Membership uses multicast, it will call <code>java.net.MulticastSocket.setLoopbackMode(localLoopbackDisabled)</code>. |
| When <code>localLoopbackDisabled==true</code> multicast messages will not reach other nodes on the same local machine. |
| The default is <code>false</code>. <br/> |
| </p> |
| </attribute> |
| |
| |
| </attributes> |
| |
| |
| </subsection> |
| |
| |
| </section> |
| |
| |
| </body> |
| |
| </document> |