Fabian Hueske created FLINK-8487:
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Summary: 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
Fix For: 1.5.0, 1.4.1
A user [reported this
issue|https://lists.apache.org/thread.html/9dc9b719cf8449067ad01114fedb75d1beac7b4dff171acdcc24903d@%3Cuser.flink.apache.org%3E]
on the [email protected] 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.
[[email protected]], can you have a look at this issue and check if it
is relevant?
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