We have created a kcs article [1] for how to switch from the default udp to tcp clustering in EPP 5.

The switch in EPP 5.1.1 is much easier than in the previous version. Here is the instruction in 5.1.1:

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Workaround for EPP 5.1.1
The following manual configuration changes are still required with EPP 5.1.1:

1. Ensure that the EPP 5.1.1 instance is set up to take the JCR configuration files from the file system. The $EPP_HOME/jboss-as/server/$CONFIG/conf/gatein/configuration.properties settings should look like this (note the 'war:' prefix!)

gatein.jcr.cache.config=war:/conf/jcr/jbosscache/${gatein.jcr.config.type}/config.xml
gatein.jcr.lock.cache.config=war:/conf/jcr/jbosscache/${gatein.jcr.config.type}/lock-config.xml
gatein.jcr.index.cache.config=war:/conf/jcr/jbosscache/cluster/indexer-config.xml
gatein.jcr.jgroups.config=war:/conf/jcr/jbosscache/cluster/udp-mux.xml
To change the jgroups stack from UDP to TCP:

2. Open the following 3 files and replace 'jcr.stack' with 'jcr.stack.tcp'
./conf/jcr/jbosscache/cluster/lock-config.xml
./conf/jcr/jbosscache/cluster/config.xml
./conf/jcr/jbosscache/cluster/indexer-config.xml

3. Open conf/jcr/jbosscache/cluster/udp-mux.xml and add a new jgroups stack named 'jcr.stack.tcp':

<protocol_stacks>
   <stack name="jcr.stack">
      <config>
         <UDP 
         [...]
    </stack>

    <!-- a new stack based on TCP -->
    <stack name="jcr.stack.tcp">
        <config>
            <TCP
         [...]
    </stack>
The  <config> element for this stack could be taken from the default  'tcp' stack definition in  deploy/cluster/jgroups-channelfactory.sar/META-INF/jgroups-channelfactory-stacks.xml

4. Open conf/organization/picketlink-idm/jboss-cache-api-cluster.xml and change the <jgroupsConfig..> element to:

  <clustering mode="replication" clusterName="${jboss.partition.name:DefaultPartition}-idm-api-cluster">
      <jgroupsConfig>
        <TCP
        [SNIP - the complete jgroupsConfig stack as defined within the 'jcr.stack.tcp' above, inside the <config> element]
        <pbcast.FLUSH timeout="0" start_flush_timeout="10000"/>    
      </jgroupsConfig>
  </clustering>
5. Open conf/organization/picketlink-idm/jboss-cache-store-cluster.xml and change the <jgroupsConfig..> element to:

  <clustering mode="replication" clusterName="${jboss.partition.name:DefaultPartition}-idm-store-cluster">
      <jgroupsConfig>
        <TCP
        [SNIP - the complete jgroupsConfig stack as defined within the 'jcr.stack.tcp' above, inside the <config> element]
        <pbcast.FLUSH timeout="0" start_flush_timeout="10000"/>    
      </jgroupsConfig>
  </clustering>
6. Before starting the server, make sure to delete the current JCR configuration settings, by following the instructions in https://access.redhat.com/kb/docs/DOC-47058

7. Make sure to start the server with the following options:

./bin/run.sh -c $CONFIG -Dexo.profiles=cluster -Djboss.default.jgroups.stack=tcp

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EPP 5.2 further simplifies the switch:

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   1.  set gatein.jcr.jgroups.config in $EPP_HOME/jboss-as/server/$CONFIG/conf/gatein/configuration.properties as:
gatein.jcr.jgroups.config=classpath:/jgroups/gatein-${gatein.default.jgroups.stack:tcp}.xml
   2.  set all of the entries of "jgroupsConfig" as <jgroupsConfig configFile="jgroups/gatein-${gatein.default.jgroups.stack:tcp}.xml" />

        in following files:

        gatein.ear/02portal.war/WEB-INF/conf/jbosscache/cluster/config.xml

        gatein.ear/02portal.war/WEB-INF/conf/jcr/jbosscache/cluster/lock-config.xml

        gatein.ear/02portal.war/WEB-INF/conf/jcr/jbosscache/cluster/indexer-config.xml

        gatein.ear/02portal.war/WEB-INF/conf/jcr/jbosscache/cluster/indexer-config.xml

        gatein.ear/02portal.war/WEB-INF/conf/organization/picketlink-idm/jboss-cache-store-cluster.xml

        gatein.ear/02portal.war/WEB-INF/conf/organization/picketlink-idm/jboss-cache-api-cluster.xml

  3.   Before starting the server, make sure to delete the current JCR configuration settings, by following the instructions inhttps://access.redhat.com/kb/docs/DOC-47058
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However, in EPP 5.2 you still have to manually edit 6 files to make the switch happen.

Can we consider to take further step to make this process even easier?

options:

1) only change a variable defined in $EPP_HOME/jboss-as/server/$CONFIG/conf/gatein/configuration.properties

2) passing a system property when starting the EPP instance

[1] https://access.redhat.com/knowledge/solutions/44761