Chapter 36. High Availability Using Server Hinting

Server Hinting helps you achieve high availability with your Red Hat JBoss Data Grid deployment.

To use Server Hinting, you provide information about the physical topology with attributes that identify servers, racks, or data centers to achieve more resilience with your data in the event that all the nodes in a given physical location become unavailable.

When you configure Server Hinting, JBoss Data Grid uses the location information you provided to distribute data across the cluster so that backup copies of data are stored on as many servers, racks, and data centers as possible.

In some cases JBoss Data Grid stores copies of data on nodes that share the same physical location. For example, if the number of owners for segments is greater than the number of distinct sites, then JBoss Data Grid assigns more than one owner for a given segment in the same site.

Consistent Hashing controls how data is distributed across nodes. JBoss Data Grid uses TopologyAwareSyncConsistentHashFactory if you enable Server Hinting. For policy configuration details, see ConsistentHashFactories in the Developer Guide.

When setting up a clustered environment in Red Hat JBoss Data Grid, Server Hinting is configured when establishing JGroups configuration.

JBoss Data Grid ships with several JGroups files pre-configured for clustered mode. These files can be used as a starting point when configuring Server Hinting in JBoss Data Grid.

See Also: Pre-Configured JGroups Files

You configure Server Hinting with the following attributes:

In Remote Client-Server mode, you configure Server Hinting in the JGroups subsystem on the transport element for the default stack, as in the following example:

<subsystem xmlns="urn:jboss:domain:jgroups:3.0"
	   default-stack="${jboss.default.jgroups.stack:udp}">
	<stack name="udp">
		<transport type="UDP"
			   socket-binding="jgroups-udp"
			   site="${jboss.jgroups.transport.site:s1}"
			   rack="${jboss.jgroups.transport.rack:r1}"
			   machine="${jboss.jgroups.transport.machine:m1}">
			   <!-- Additional configuration elements here -->
		</transport>
	</stack>
</subsystem>

<subsystem xmlns="urn:jboss:domain:jgroups:3.0"
	   default-stack="${jboss.default.jgroups.stack:udp}">
	<stack name="udp">
		<transport type="UDP"
			   socket-binding="jgroups-udp"
			   site="${jboss.jgroups.transport.site:s1}"
			   rack="${jboss.jgroups.transport.rack:r1}"
			   machine="${jboss.jgroups.transport.machine:m1}">
			   <!-- Additional configuration elements here -->
		</transport>
	</stack>
</subsystem>

In Library mode, you configure Server Hinting at the transport level, as in the following example:

<transport cluster = "MyCluster"
           machine = "LinuxServer01"
           rack = "Rack01"
           site = "US-WestCoast"
           node-name = "Node01" />

<transport cluster = "MyCluster"
           machine = "LinuxServer01"
           rack = "Rack01"
           site = "US-WestCoast"
           node-name = "Node01" />