[jboss-jira] [JBoss JIRA] Resolved: (JGRP-598) Simplify FLUSH

Simplify FLUSH -------------- Key: JGRP-598 URL: http://jira.jboss.com/jira/browse/JGRP-598 Project: JGroups Issue Type: Task Affects Versions: 2.4, 2.5 Reporter: Vladimir Blagojevic Assigned To: Vladimir Blagojevic Fix For: 2.6 #1 Superfluous FLUSH-COMPLETED phase ? -------------------------------------- It seems we don't need the FLUSH-COMPLETED phase, it is sufficient for the FLUSH leader to do a START-FLUSH and wait for all FLUSH-OK messages. Why ? Because the reconciliation protocol will reconcile messages before the view installation (or state transfer). Example: {A,B,C}. E sends message M and then crashes. Only C receives M. - A does a START-FLUSH - B and C send a FLUSH-OK back to A. This means that all multicasts from B will be seen by A *before* B's FLUSH-OK is received, and all multicasts from C will be seen by A before C's FLUSH-OK is received by A. HOWEVER, C will not necessarily send M to A before sending the FLUSH-OK message. This is only done through the reconciliation protocol ! - FLUSH-COMPLETED can be removed, the digest that's part of FLUSH-COMPLETED has to moved to FKLUSH-OK phase. - FLUSH-OK is unicast *not* multicast. #2 Superfluous STOP-FLUSH-OK phase ? ------------------------------------ Why do we need the acks here ? JGroups guarantees the STOP-FLUSH message is delivered to all non-faulty members, so why wait fr the STOP-FLUSH-OK ? If we make STOP-FLUSH *OOB* (JGRP-337), then this should work ! We can get rid of STOP-FLUSH-OK !! Just send STOP-FLUSH as OOB multicast. Note: this requires the concurrent stack, so possibly check for concurrent stack. Throw an exception if concurrent stack is not present when FLUSH is used. So, these changes cannot be applied to 2.4, only to 2.5 and 2.6. #3 Timeouts ----------- - ClientGmsImpl: has a hard coded timeout of 4 secs - CoordGmsImpl also has a timeout for block() - If we *need* timeouts, we should get them from the FLUSH protocol ! CoorsGmsImpl.startFlush() should *not* have a timeout, this should be in FLUSH itself. startFlush() should block forever, until it gets the ack #4 Spurious FLUSH-OK in the diagram ----------------------------------- In the JOIN diagram, probably also in the state transfer diagram