[jboss-jira] [JBoss JIRA] (JGRP-1495) SEQUENCER delivers messages and views out of order

SEQUENCER delivers messages and views out of order -------------------------------------------------- Key: JGRP-1495 URL: https://issues.jboss.org/browse/JGRP-1495 Project: JGroups Issue Type: Feature Request Affects Versions: 3.1 Reporter: David Hotham Assignee: Bela Ban I first raised this, or something very like it, in JGRP-1468; but it got lost among the other fixes that were made in that issue. I've just seen a case where after a merge-view the following happens at a node W: {noformat} SEQUENCER GMS APPLICATION | | | B (view) | | | ------------>| | | |----------------->| | | |----\ | C (view) | | \ | ------------>| | \ | |----------------->| \ | | | \ | C (msg) | | | | ------------>| | | | |---------------------------|-------->| | | | | | | \ | | | \------->| {noformat} - Initially the view is {B,W} - There's a merge view, in which B and C were the old coordinators - B and C both broadcast the new view {B,C,T,W}. In fact both know the physical address of the member shown above (or we're using UDP multicast, if you like); so the view is sent to this node twice. - B's view arrives on thread Incoming-1, and gets as far as GMS - C's view arrives on thread Incoming-2, and gets as far as GMS (where it is dropped, since it is the same view) - A message from C, prompted by the change in view, arrives on thread Incoming-2 - This overtakes the view on thread Incoming-1, and is delivered to the application - Only then does thread Incoming-1 get to deliver the view to the application ie from the application's point of view: C broadcast the view and then the message; whereas at the node shown above the application received the message and then the view. I think that the fix will simply be to put a lock in SEQUENCER around up_prot.up(evt) in SEQUENCER.deliver(). That way messages will be delivered to the application in the same order as they arrive at SEQUENCER. Edit: updated description for clarity