Multicast (PGM) Cluster Member Discovery

The discover URL for multicast discovery uses PGM (Pragmatic General Multicast) protocol.

The discovery property is be.engine.cluster.as.discover.url. For multicast discovery, the value is a URL with the following format: 

tibpgm://destinationPort/network/

The default value for the URL equates to the following value:

//7888/;239.8.8.9/

Specify the parameters as follows.

Parameter Notes 
destinationPort
 Specifies the destination port used by the PGM transport.

Must be the same value on all machines in the cluster.

The default value is 7888. 

network
 Specifies the IP address of the interface to be used for sending multicast packets, and the multicast group address to be used.

The format is as follows: interface;multicast group address

The value for interface is unique to a node. It must also be the same in both the discovery and the listen URLs for a node. If there are multiple interfaces on one machine, specify the interface you want to use and do not rely on the default value.

The value for multicast group address must be the same on all machines in the cluster.

The default value for interface is the first available interface provided by the operating system hosts file for the machine.

Note
 If the desired interface is not listed in the hosts file then PGM picks the first available interface in the file. (On most operating systems, this file is called the /etc/hosts file.) If the first interface is the loopback interface (127.0.0.1) then PGM fails to start. In this case you would see a stacktrace exception in the log file such as the following: 
SYS_ERROR (multicast_error - (8) grp_iface not a valid multicast interface)

To resolve this issue, either modify the hosts file, or provide the desired interface explicitly in the network argument.

The default value for multicast group address is the multicast group address as 239.8.8.9.