JGroups Protocol GMS

Internal

• JGroups

Suspected Member Exclusion

If a SUSPECT message survives VERIFY_SUSPECT verification, it is passed up the stack and reaches the GMS layer, which computes and multicasts a new view. The new view does not contain the suspect member:

2016-02-29 09:25:24,110 [TRACE] [org.jgroups.protocols.pbcast.GMS] (ViewHandler,TEST-CLUSTER,host01/tcp) -- host01/tcp: joiners=[], suspected=[host02/tcp], leaving=[], new view: [host01/tcp|3] (2) [host01/tcp, host03/tcp]
2016-02-29 09:25:24,110 [TRACE] [org.jgroups.protocols.pbcast.GMS] (ViewHandler,TEST-CLUSTER,host01/tcp) -- host01/tcp: mcasting view [host01/tcp|3] (2) [host01/tcp, host03/tcp] (2 mbrs)

The log sequence above shows how "host02" is removed from the [host01, host02, host03] view.

This is how the VIEW message looks at the transport level:

2016-02-29 09:25:24,125 [TRACE] [org.jgroups.protocols.TCP] (ViewHandler,TEST-CLUSTER,host01/tcp) -- null: sending msg to null, src=host01/tcp, headers are GMS: GmsHeader[VIEW], NAKACK2: [MSG, seqno=434687], TCP: [channel_name=TEST-CLUSTER]

The new view is installed at the GMS level - including for the coordinator that originated it - when the multicast message propagates up from the transport to the GMS protocol. The DEBUG message shown below should be visible in all members' logs:

2016-02-29 09:25:24,157 [TRACE] [org.jgroups.protocols.pbcast.GMS] (Cluster Dispatch) -- host01/tcp: received delta view [host01/tcp|3], ref-view=[host01/tcp|2], left=[host02/tcp]
2016-02-29 09:25:24,157 [DEBUG] [org.jgroups.protocols.pbcast.GMS] (Cluster Dispatch) -- host01/tcp: installing view [host01/tcp|3] (2) [host01/tcp, host03/tcp]