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https://issues.apache.org/jira/browse/ZOOKEEPER-2380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15342690#comment-15342690
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Arshad Mohammad commented on ZOOKEEPER-2380:
--------------------------------------------
It enters into FOLLOWING state when fix is applied. If the code fix is not
applied it will not enter into FOLLOWING state. Can you please apply only test
code modification and run the test case to verify the efficacy of code and test
code.
> Deadlock between leader shutdown and forwarding ACK to the leader
> -----------------------------------------------------------------
>
> Key: ZOOKEEPER-2380
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2380
> Project: ZooKeeper
> Issue Type: Bug
> Components: server
> Reporter: Arshad Mohammad
> Assignee: Arshad Mohammad
> Priority: Blocker
> Fix For: 3.5.2, 3.6.0
>
> Attachments: ZOOKEEPER-2380-01.patch, ZOOKEEPER-2380-02.patch,
> ZOOKEEPER-2380-03.patch, ZOOKEEPER-2380-04.patch, ZOOKEEPER-2380-05.patch,
> ZOOKEEPER-2380-06.patch, ZOOKEEPER-2380-fail.out
>
>
> Zookeeper enters into deadlock while shutting down itself, thus making
> zookeeper service unavailable as deadlocked server is a leader. Here is the
> thread dump:
> {code}
> "QuorumPeer[myid=1](plain=/0:0:0:0:0:0:0:0:2181)(secure=disabled)" #25 prio=5
> os_prio=0 tid=0x00007fbc502a6800 nid=0x834 in Object.wait()
> [0x00007fbc4d9a8000] java.lang.Thread.State: WAITING (on object monitor)
> at java.lang.Object.wait(Native Method) at
> java.lang.Thread.join(Thread.java:1245) - locked <
> 0x00000000feb78000> (a org.apache.zookeeper.server.SyncRequestProcessor)
> at java.lang.Thread.join(Thread.java:1319) at
> org.apache.zookeeper.server.SyncRequestProcessor.shutdown(SyncRequestProcessor.java:196)
> at
> org.apache.zookeeper.server.quorum.ProposalRequestProcessor.shutdown(ProposalRequestProcessor.java:90)
> at
> org.apache.zookeeper.server.PrepRequestProcessor.shutdown(PrepRequestProcessor.java:1016)
> at
> org.apache.zookeeper.server.quorum.LeaderRequestProcessor.shutdown(LeaderRequestProcessor.java:78)
> at
> org.apache.zookeeper.server.ZooKeeperServer.shutdown(ZooKeeperServer.java:561)
> - locked <
> 0x00000000feb61e20> (a
> org.apache.zookeeper.server.quorum.LeaderZooKeeperServer) at
> org.apache.zookeeper.server.quorum.QuorumZooKeeperServer.shutdown(QuorumZooKeeperServer.java:169)
> - locked <
> 0x00000000feb61e20> (a
> org.apache.zookeeper.server.quorum.LeaderZooKeeperServer) at
> org.apache.zookeeper.server.quorum.LeaderZooKeeperServer.shutdown(LeaderZooKeeperServer.java:102)
> - locked <
> 0x00000000feb61e20> (a
> org.apache.zookeeper.server.quorum.LeaderZooKeeperServer) at
> org.apache.zookeeper.server.quorum.Leader.shutdown(Leader.java:637) at
> org.apache.zookeeper.server.quorum.Leader.lead(Leader.java:590) - locked
> <
> 0x00000000feb781a0> (a org.apache.zookeeper.server.quorum.Leader) at
> org.apache.zookeeper.server.quorum.QuorumPeer.run(QuorumPeer.java:1108)
> "SyncThread:1" #46 prio=5 os_prio=0 tid=0x00007fbc5848f000 nid=0x867 waiting
> for monitor entry [0x00007fbc4ca90000] java.lang.Thread.State: BLOCKED
> (on object monitor) at
> org.apache.zookeeper.server.quorum.Leader.processAck(Leader.java:784) -
> waiting to lock <0x00000000feb781a0> (a
> org.apache.zookeeper.server.quorum.Leader) at
> org.apache.zookeeper.server.quorum.AckRequestProcessor.processRequest(AckRequestProcessor.java:46)
> at
> org.apache.zookeeper.server.SyncRequestProcessor.flush(SyncRequestProcessor.java:183)
> at
> org.apache.zookeeper.server.SyncRequestProcessor.run(SyncRequestProcessor.java:113)
> {code}
> Leader.lead() calls shutdown() from the synchronized block, it acquired lock
> on Leader.java instance
> {code}
> while (true) {
> synchronized (this) {
> long start = Time.currentElapsedTime();
> .....
> {code}
> In the shutdown flow SyncThread is trying to acquire lock on the same
> Leader.java instance.
> Leader thread acquired lock and waiting for SyncThread shutdown. SyncThread
> waiting for the lock to complete its shutdown. This is how ZooKeeper entered
> into deadlock
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