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From Subramanian Raghunathan <subramanian.raghunat...@integral.com>
Subject Double assignment , when participant is not able to establish connection with zookeeper quorum
Date Thu, 26 Jan 2017 00:17:26 GMT
Hi ,

Double assignment , when participant is not able to establish connection with zookeeper quorum

Following is the  set up.

Version(s) :
                                Helix: 0.7.1
                                Zookeeper:3.3.4

- State Model: OnlineOffline
- Controller (leader elected from one of the cluster nodes)
- Single resources with partitions.
- Full auto rebalancer

-Zookeeper quorum (3 nodes)

When one participant loses the zookeeper connection (It's not able to connect to any of the
zookeepers , a typical occurrence we faced was switch failure from that rack)

  ---- >  The partition (P1) for which this participant (say Node N1) is online is still
maintained

Meanwhile since it loses the ephemeral  node in zookeeper , the rebalancer gets triggered
and it reallocates the partition (P1) to another participant node (say Node N2) to become
online  @ time T1

                ---- >  After this both N1 and N2 are acting as online for the same Partition
(P1)

But as soon as participant in (say Node N1) is able to re-establish the zookeeper connection
 @ time T2
                ---- >  Reset gets called on the partition in participant (say Node N1)

Double assignment:
The question here is this an expected behavior that both nodes N1 and N2 could be online for
the same Partition (P1) between time (T1-T2) ? Any responses on the same would be appreciated.

Thanks & Regards,
Subramanian.

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Palo Alto, CA 94304
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