ASF GitHub Bot commented on FLINK-8487:

GitHub user aljoscha opened a pull request:


    [FLINK-8487] Verify ZooKeeper checkpoint store behaviour with ITCase

    R: @zentol 

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/aljoscha/flink 

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To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #5654
commit 62c6695c61c628ef842c6a29dbb517d71e50ca59
Author: Aljoscha Krettek <aljoscha.krettek@...>
Date:   2018-03-03T08:34:56Z

    [FLINK-8487] Verify ZooKeeper checkpoint store behaviour with ITCase


> 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.
> [~stefanrichte...@gmail.com], can you have a look at this issue and check if 
> it is relevant?

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