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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-8487) State loss after multiple restart attempts
Date Wed, 07 Mar 2018 14:54:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-8487?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16389652#comment-16389652
] 

ASF GitHub Bot commented on FLINK-8487:
---------------------------------------

Github user aljoscha commented on the issue:

    https://github.com/apache/flink/pull/5656
  
    We shouldn't look at this one anyways because we can't merge it on master unless the other
stuff is in. Because the test will not work.


> State loss after multiple restart attempts
> ------------------------------------------
>
>                 Key: FLINK-8487
>                 URL: https://issues.apache.org/jira/browse/FLINK-8487
>             Project: Flink
>          Issue Type: Bug
>          Components: State Backends, Checkpointing
>    Affects Versions: 1.3.2
>            Reporter: Fabian Hueske
>            Priority: Blocker
>             Fix For: 1.5.0, 1.4.3
>
>
> A user [reported this issue|https://lists.apache.org/thread.html/9dc9b719cf8449067ad01114fedb75d1beac7b4dff171acdcc24903d@%3Cuser.flink.apache.org%3E]
on the user@f.a.o mailing list and analyzed the situation.
> Scenario:
> - A program that reads from Kafka and computes counts in a keyed 15 minute tumbling window.
 StateBackend is RocksDB and checkpointing is enabled.
> {code}
> keyBy(0)
>         .timeWindow(Time.of(window_size, TimeUnit.MINUTES))
>         .allowedLateness(Time.of(late_by, TimeUnit.SECONDS))
>         .reduce(new ReduceFunction(), new WindowFunction())
> {code}
> - At some point HDFS went into a safe mode due to NameNode issues
> - The following exception was thrown
> {code}
> org.apache.hadoop.ipc.RemoteException(org.apache.hadoop.ipc.StandbyException): Operation
category WRITE is not supported in state standby. Visit https://s.apache.org/sbnn-error
>     ..................
>     at org.apache.flink.runtime.fs.hdfs.HadoopFileSystem.mkdirs(HadoopFileSystem.java:453)
>         at org.apache.flink.core.fs.SafetyNetWrapperFileSystem.mkdirs(SafetyNetWrapperFileSystem.java:111)
>         at org.apache.flink.runtime.state.filesystem.FsCheckpointStreamFactory.createBasePath(FsCheckpointStreamFactory.java:132)
> {code}
> - The pipeline came back after a few restarts and checkpoint failures, after the HDFS
issues were resolved.
> - It was evident that operator state was lost. Either it was the Kafka consumer that
kept on advancing it's offset between a start and the next checkpoint failure (a minute's
worth) or the the operator that had partial aggregates was lost. 
> The user did some in-depth analysis (see [mail thread|https://lists.apache.org/thread.html/9dc9b719cf8449067ad01114fedb75d1beac7b4dff171acdcc24903d@%3Cuser.flink.apache.org%3E])
and might have (according to [~aljoscha]) identified the problem.
> [~stefanrichter83@gmail.com], can you have a look at this issue and check if it is relevant?



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