[jboss-jira] [JBoss JIRA] (JGRP-1401) RELAY2: messages lost when local site master crashes

[Bela Ban (JIRA)]

    [ https://issues.jboss.org/browse/JGRP-1401?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12718969#comment-12718969 ] 

Bela Ban commented on JGRP-1401:
--------------------------------

We don't currently handle ordering of messages sent in parallel to resending of previously queued messages. (This problem is similar to SEQUENCER.)

Not a big issue for sync RPCs, as we're waiting for the call to complete anyway before invoking a new RPC. However, this *does* affect async RPCs...
                
> RELAY2: messages lost when local site master crashes
> ----------------------------------------------------
>
>                 Key: JGRP-1401
>                 URL: https://issues.jboss.org/browse/JGRP-1401
>             Project: JGroups
>          Issue Type: Feature Request
>            Reporter: Bela Ban
>            Assignee: Bela Ban
>             Fix For: 3.2
>
>
> When we have sites LON={A,B,C} and SFO={X,Y,Z}, if C wants to send a unicast message to the site master of SFO (X), but the *local site master (A)* leaves or crashes, and B hasn't taken over yet, the message will be lost.
> The idea to solve this is to forward the message to the next coordinator if the current coordinator leaves or dies.
> A FORWARD_TO_COORD protocol was developed, which handles this task. RELAY2 checks at startup if FORWARD_TO_COORD is present and uses a FORWARD event to tell that protocol to forward a message to the current coordinator. If the protocol is not present, a simple unicast will be sent (unreliably).
> FORWARD_TO_COORD sends a message M to the current coord and removes M when an ack has been received. If there is a view change, indicating the old coord left, it resends all pending messages, and so on. The extreme case would be that everyone but the sender dies and then M would be sent to the sender itself.

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