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https://issues.apache.org/jira/browse/ZOOKEEPER-2380?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15229774#comment-15229774
]
Rakesh R commented on ZOOKEEPER-2380:
-------------------------------------
Thanks [~arshad.mohammad] for the updates. Overall patch looks good, please
take a look at the following comments.
# In RaceConditionTest.java, it uses tab space. Please change the indentation
by using spaces instead of tabs.
# Please change {{null != quorumPeer}} checks to {{quorumPeer != null}}, we are
using this fashion and would be good to follow same way.
# Please remove the following overridden method {{#runFromConfig()}} from class
TestQPMain, its not required.
{code}
@Override
public void runFromConfig(QuorumPeerConfig config) throws IOException,
AdminServerException {
super.runFromConfig(config);
}
{code}
Also, remove unused code.
{code}
/**
* it is same as Container feature is disabled
*/
// setupContainerManager();
{code}
# Make the following methods to use private access specifier
{code}
static class MockTestQPMain
static class MockSyncRequestProcessor
static class MockProposalRequestProcessor
protected MainThread[] startQuorum()
{code}
# Change {{e.printStackTrace();}} to LOG.warn("") messaging
# {{"Leader must have gone into LOOKING state"}}, here it should be {{Leader
failed to transition to LOOKING state}}, right?
# Good unit test. Could you please write the sequence of steps which results in
deadlock in the unit test case, that would help to maintain it well and convey
the idea quickly to others.
> Deadlock while shutting down the zookeeper
> ------------------------------------------
>
> 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 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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