A.4. The TCPGOSSIP JGroups Protocol

The TCPGOSSIP discovery protocol uses one or more configured GossipRouter processes to store information about the nodes in the cluster.

Important

It is vital that the GossipRouter process consistently be available to all nodes in the cluster, as without this process it will not be possible to add additional nodes. For this reason it is strongly recommended to deploy this process in a highly available method; for example, an Availability Set with multiple virtual machines may be used.
Running the GossipRouter

The GossipRouter is included in the JGroups jar file, and must be running before any nodes are started. This process may be started by pointing to the GossipRouter class in the JGroups jar file included with JBoss Data Grid: 

java -classpath jgroups-${jgroups.version}.jar org.jgroups.stack.GossipRouter -bindaddress IP_ADDRESS -port PORT

In the event that multiple GossipRouters are available, and specified, a node will always register with all specified GossipRouters; however, it will only retrieve information from the first available GossipRouter. If a GossipRouter is unavailable it will be marked as failed and removed from the list, with a background thread started to periodically attempt reconnecting to the failed GossipRouter. Once the thread successfully reconnects the GossipRouter will be reinserted into the list.
Configuring JBoss Data Grid to use TCPGOSSIP (Library Mode)

In Library Mode the JGroups xml file should be used to configure TCPGOSSIP; however, there is no TCPGOSSIP configuration included by default. It is recommended to use one of the preexisting files specified in Section 30.2.2, “Pre-Configured JGroups Files” and then adjust the configuration to include TCPGOSSIP. For instance, default-configs/default-jgroups-ec2.xml could be selected and the S3_PING protocol removed, and then the following block added in its place: 

<TCPGOSSIP initial_hosts="IP_ADDRESS_0[PORT_0],IP_ADDRESS_1[PORT_1]" />

Configuring JBoss Data Grid to use TCPGOSSIP (Remote Client-Server Mode)

In Remote Client-Server Mode a stack may be defined for TCPGOSSIP in the jgroups subsystem of the server's configuration file. The following configuration snippet contains an example of this: 

<subsystem xmlns="urn:infinispan:server:jgroups:8.0" default-stack="${jboss.default.jgroups.stack:tcpgossip}">
[...]
    <stack name="jdbc_ping">
        <transport type="TCP" socket-binding="jgroups-tcp"/>
        <protocol type="TCPGOSSIP">
            <property name="initial_hosts">IP_ADDRESS_0[PORT_0],IP_ADDRESS_1[PORT_1]</property>
        </protocol>
        <protocol type="MERGE3"/>
        <protocol type="FD_SOCK" socket-binding="jgroups-tcp-fd"/>
        <protocol type="FD_ALL"/>
        <protocol type="VERIFY_SUSPECT"/>
        <protocol type="pbcast.NAKACK2">
            <property name="use_mcast_xmit">false</property>
        </protocol>
        <protocol type="UNICAST3"/>
        <protocol type="pbcast.STABLE"/>
        <protocol type="pbcast.GMS"/>
        <protocol type="MFC"/>
        <protocol type="FRAG2"/>
    </stack>
[...]
</subsystem>

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