[jboss-jira] [JBoss JIRA] (JGRP-1977) More redundant initial join logic to avoid becoming a fake coordinator

[Bela Ban (JIRA)]

     [ https://issues.jboss.org/browse/JGRP-1977?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Bela Ban resolved JGRP-1977.
----------------------------
    Resolution: Rejected


If an IGMP join message followed by a multicast causes the multicast to be dropped, then I consider this an incorrect network configuration. Even sending the discovery message multiple times may not help, as you indicated the merge only happen multiple minutes later. It seems the multicast routing table on a switch is not updated for multiple minutes.

> More redundant initial join logic to avoid becoming a fake coordinator
> ----------------------------------------------------------------------
>
>                 Key: JGRP-1977
>                 URL: https://issues.jboss.org/browse/JGRP-1977
>             Project: JGroups
>          Issue Type: Enhancement
>            Reporter: Osamu Nagano
>            Assignee: Bela Ban
>             Fix For: 3.6.7
>
>
> If the very initial JGroups discovery packet is lost, it is never recovered by the current GMS join logic.  The node will be a standalone coordinator then merges after several minutes.
> This can happen if a new node reside in another network segment and a switch between the segments requires some time to establish a new multicast route.  Currently, there is no enough time between IGMP join (by {{MulticastSocket#joinGroup()}}) and the JGroups discovery packet and the later is lost in such a network environment.  Because the number of nodes can be very large, configuring a static route in the switch is not reasonable.
> Specifically, in method {{org.jgroups.protocols.pbcast.ClientGmsImpl#joinInternal()}}, part of {{gms.getDownProtocol().down(Event.FIND_INITIAL_MBRS_EVT)}} is outside of the retry loop of GMS.max_join_attempts and GMS.join_timeout.



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