Chapter 19 Configuring Cache Cluster Discovery : Discovering Cache Cluster Members Using Multicast

Discovering Cache Cluster Members Using Multicast
With multicast cache cluster configuration, the cluster membership is established using the multicast IP address and port. When a BusinessEvents node subscribes to this multicast IP address it broadcasts information about its presence to the address.
If the default values for the multicast properties values work for your environment, then you don’t have to configure any multicast properties. You need only define a cluster name in the property file for each engine (node) of the cluster.
Below is an example showing the properties with their defaults:

 
java.property.tangosol.coherence.clusteraddress=224.3.3.1
java.property.tangosol.coherence.clusterport=33389
java.property.tangosol.coherence.ttl=0

 
Adding, Removing, and Moving Nodes
The object management layer uses multicast to discover new nodes and add them to the cache cluster. Similarly when nodes are removed or moved to a different server, the multicast protocol ensures that members are kept current without any additional configuration.
To Configure Multicast Settings
The properties for each node in the cluster must be set to the same values.
1.
java.property.tangosol.coherence.cluster=cluster_name
2.
If the default multicast configuration address and port does not work for your environment, add the following properties, specifying the appropriate value:
java.property.tangosol.coherence.clusteraddress=cluster_address
java.property.tangosol.coherence.clusterport=cluster_port
 
java.property.tangosol.coherence.cluster
java.property.tangosol.coherence.clusteraddress
java.property.tangosol.coherence.clusterport
Specifies the time-to-live setting for the multicast, that is, the maximum number of "hops" a packet can traverse. A hop is defined as a traversal from one network segment to another via a router.
On a single-host cluster, set to zero (0). On a simple switched backbone, set to 1. On an advanced backbone with intelligent switching, it may require a value of 2 or more.
Setting the value too high can use unnecessary bandwidth on other LAN segments and can even cause the operating system or network devices to disable multicast traffic.
Note: While a value of 0 is intended to keep packets from leaving the originating machine, some operating systems do not implement this correctly, and the packets may in fact be transmitted on the network.