[FLINK-8487] State loss after multiple restart attempts

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: 1.3.2
• Fix Version/s: 1.3.3, 1.4.3, 1.5.0
• Component/s: Runtime / State Backends
• Assignee: Aljoscha Krettek
• Reporter: Fabian Hueske
• Created: 23/Jan/18 09:12
• Updated: 11/Mar/18 15:44
• Resolved: 11/Mar/18 15:44

Description

A user reported this issue 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.

keyBy(0)
        .timeWindow(Time.of(window_size, TimeUnit.MINUTES))
        .allowedLateness(Time.of(late_by, TimeUnit.SECONDS))
        .reduce(new ReduceFunction(), new WindowFunction())

• At some point HDFS went into a safe mode due to NameNode issues
• The following exception was thrown

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)

• 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) and might have (according to aljoscha) identified the problem.

[e-mail], can you have a look at this issue and check if it is relevant?

Issue Links

• links to: GitHub Pull Request #5654
• links to: GitHub Pull Request #5655
• links to: GitHub Pull Request #5656