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https://issues.apache.org/jira/browse/ZOOKEEPER-1026?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13010281#comment-13010281
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Jeremy Stribling commented on ZOOKEEPER-1026:
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Wow, thanks for the in-depth explanation. It makes sense to me, in terms of
the timeline of events and what could go wrong, but I don't know enough about
the Zookeeper code to be able to verify for sure. I would love to try out a
patch for ZOOKEEPER-975 and see if that fixes the problem for me. (I added
myself as a watcher for that bug.)
> Sequence number assignment decreases after old node rejoins cluster
> -------------------------------------------------------------------
>
> Key: ZOOKEEPER-1026
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1026
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Affects Versions: 3.3.3
> Reporter: Jeremy Stribling
> Attachments: ZOOKEEPER-1026.logs.tgz
>
>
> I ran into a weird case where a Zookeeper server rejoins the cluster after
> missing several operations, and then a client creates a new sequential node
> that has a number earlier than the last node it created. I don't have full
> logs, or a live system in this state, or any data directories, just some
> partial server logs and the evidence as seen by the client. Haven't tried
> reproducing it yet, just wanted to see if anyone here had any ideas. Here's
> the scenario (probably more info than necessary, but trying to be complete)
> 1) Initially (5:37:20): 3 nodes up, with ids 215, 126, and 37 (called nodes
> #1, #2, and #3 below):
> 2) Nodes periodically (and throughout this whole timeline) create sequential,
> non-ephemeral nodes under the /zkrsm parent node.
> 3) 5:46:57: Node #1 gets notified of /zkrsm/0000000000000000_record0000002116
> 4) 5:47:06: Node #1 restarts and rejoins
> 5) 5:49:26: Node #2 gets notified of /zkrsm/0000000000000000_record0000002708
> 6) 5:49:29: Node #2 restarts and rejoins
> 7) 5:52:01: Node #3 gets notified of /zkrsm/0000000000000000_record0000003291
> 8) 5:52:02: Node #3 restarts and begins the rejoining process
> 9) 5:52:08: Node #1 successfully creates
> /zkrsm/0000000000000000_record0000003348
> 10) 5:52:08: Node #2 dies after getting notified of
> /zkrsm/0000000000000000_record0000003348
> 11) 5:52:10ish: Node #3 is elected leader (the ZK server log doesn't have
> wallclock timestamps, so not exactly sure on the ordering of this step)
> 12) 5:52:15: Node #1 successfully creates
> /zkrsm/0000000000000000_record0000003292
> Note that the node created in step #12 is lower than the one created in step
> #9, and is exactly one greater than the last node seen by node #3 before it
> restarted.
> Here is the sequence of session establishments as seen from the C client of
> node #1 after its restart (the IP address of node #1=13.0.0.11, #2=13.0.0.12,
> #3=13.0.0.13):
> 2011-03-18 05:46:59,838:17454(0x7fc57d3db710):ZOO_INFO@check_events@1632:
> session establishment complete on server [13.0.0.13:2888],
> sessionId=0x252ec780a3020000, negotiated timeout=6000
> 2011-03-18 05:49:32,194:17454(0x7fc57cbda710):ZOO_INFO@check_events@1632:
> session establishment complete on server [13.0.0.13:2888],
> sessionId=0x252ec782f5100002, negotiated timeout=6000
> 2011-03-18 05:52:02,352:17454(0x7fc57d3db710):ZOO_INFO@check_events@1632:
> session establishment complete on server [13.0.0.12:2888],
> sessionId=0x7e2ec782ff5f0001, negotiated timeout=6000
> 2011-03-18 05:52:08,583:17454(0x7fc57d3db710):ZOO_INFO@check_events@1632:
> session establishment complete on server [13.0.0.11:2888],
> sessionId=0x7e2ec782ff5f0001, negotiated timeout=6000
> 2011-03-18 05:52:13,834:17454(0x7fc57cbda710):ZOO_INFO@check_events@1632:
> session establishment complete on server [13.0.0.11:2888],
> sessionId=0xd72ec7856d0f0001, negotiated timeout=6000
> I will attach logs for all nodes after each of their restarts, and a partial
> log for node #3 from before its restart.
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