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https://issues.apache.org/jira/browse/HDFS-6827?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14101262#comment-14101262
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stack commented on HDFS-6827:
-----------------------------
This issue looks a little ugly. NameNodes stuck in standby mode? This
production? What did it look like?
bq. BTW: The healthCheckLock is used to distinguish the graceful failover and
the above scenario.
I don't know this code well. How is the above done?
The code in checkServiceStatus seems 'fragile' looking for a explicity
transition. Is there a more explicit check that can be done to learn if
'service is restarted'?
In the below test, is it possible the state gets moved to standby before the
service healthy check runs? Would the test get stuck in this case?
+ // fake svc0 is restarted and change to standby, but the health monitor
+ // doesn't realize that
+ svc0.proxy.transitionToStandby(new StateChangeRequestInfo(
+ RequestSource.REQUEST_BY_ZKFC));
+
+ cluster.waitForHealthState(0, State.SERVICE_HEALTHY);
+ cluster.waitForHealthState(1, State.SERVICE_HEALTHY);
Thanks.
> Both NameNodes could be in STANDBY State due to HealthMonitor not aware of
> the target's status changing sometimes
> -----------------------------------------------------------------------------------------------------------------
>
> Key: HDFS-6827
> URL: https://issues.apache.org/jira/browse/HDFS-6827
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ha
> Affects Versions: 2.4.1
> Reporter: Zesheng Wu
> Assignee: Zesheng Wu
> Priority: Critical
> Attachments: HDFS-6827.1.patch
>
>
> In our production cluster, we encounter a scenario like this: ANN crashed due
> to write journal timeout, and was restarted by the watchdog automatically,
> but after restarting both of the NNs are standby.
> Following is the logs of the scenario:
> # NN1 is down due to write journal timeout:
> {color:red}2014-08-03,23:02:02,219{color} INFO
> org.apache.hadoop.hdfs.server.namenode.NameNode: SHUTDOWN_MSG
> # ZKFC1 detected "connection reset by peer"
> {color:red}2014-08-03,23:02:02,560{color} ERROR
> org.apache.hadoop.security.UserGroupInformation: PriviledgedActionException
> as:[email protected] (auth:KERBEROS) cause:java.io.IOException:
> {color:red}Connection reset by peer{color}
> # NN1 wat restarted successfully by the watchdog:
> 2014-08-03,23:02:07,884 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
> Web-server up at: xx:13201
> 2014-08-03,23:02:07,884 INFO org.apache.hadoop.ipc.Server: IPC Server
> Responder: starting
> {color:red}2014-08-03,23:02:07,884{color} INFO org.apache.hadoop.ipc.Server:
> IPC Server listener on 13200: starting
> 2014-08-03,23:02:08,742 INFO org.apache.hadoop.ipc.Server: RPC server clean
> thread started!
> 2014-08-03,23:02:08,743 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
> Registered DFSClientInformation MBean
> 2014-08-03,23:02:08,744 INFO org.apache.hadoop.hdfs.server.namenode.NameNode:
> NameNode up at: xx/xx:13200
> 2014-08-03,23:02:08,744 INFO
> org.apache.hadoop.hdfs.server.namenode.FSNamesystem: Starting services
> required for standby state
> # ZKFC1 retried the connection and considered NN1 was healthy
> {color:red}2014-08-03,23:02:08,292{color} INFO org.apache.hadoop.ipc.Client:
> Retrying connect to server: xx/xx:13200. Already tried 0 time(s); retry
> policy is RetryUpToMaximumCountWithFixedSleep(maxRetries=1, sleepTime=1
> SECONDS)
> # ZKFC1 still considered NN1 as a healthy Active NN, and didn't trigger the
> failover, as a result, both NNs were standby.
> The root cause of this bug is that NN is restarted too quickly and ZKFC
> health monitor doesn't realize that.
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