Discovery Attribute
The discovery attribute specifies how this instance of the metaspace discovers the current metaspace members.
The format of the discovery attribute determines the mode of connection to the metaspace (either as a full peer or as a remote client).
When your application is connecting as a full peer, the discovery attribute specifies how this instance of the metaspace is used.
Discovery can be unicast (TCP) or multicast (PGM —Pragmatic General Multicast).
There are three different discovery protocols:
To become members of the same metaspace, all intended members of a metaspace must use compatible discovery URLs. If the members do not specify compatible discovery URLs, then they are not connected to the same metaspace.
For example, if two metaspace members attempt to connect to the same metaspace using different discovery protocols, two different metaspaces are created and the two members are in different metaspaces.
- PGM (Pragmatic General Multicast) URL Format
With PGM, discovery of the current metaspace members is done by using reliable IP multicast. - TCP Discovery URL Format
When multicast discovery is not desirable or possible, you can use pure TCP discovery. - Discovery URL Format for Remote Clients for Connecting as a Remote Client
Remote clients connect to the seeder that is running as-agent by calling the Java setremoteDiscovery method.