[FLINK-12653] Keyed state backend fails to restore during rescaling

• Type: Bug
• Status: Open
• Priority: Not a Priority
• Resolution: Unresolved
• Affects Version/s: 1.6.4, 1.7.2, 1.8.0
• Component/s: Runtime / State Backends
• Labels: auto-deprioritized-critical auto-deprioritized-major auto-deprioritized-minor

Environment

Beam 2.12.0 or any other Beam version
Flink >= 1.6
Heap/Filesystem state backend (RocksDB works fine)

• Assignee: Unassigned
• Reporter: Maximilian Michels
• Created: 28/May/19 14:33
• Updated: 22/Dec/21 10:39

Description

The Flink Runner includes a test which verifies checkpoints/savepoints work correctly with Beam on Flink. When adding additional tests for scaleup/scaledown [1], I came across a bug with restoring the keyed state backend. After a fair amount of debugging Beam code and checking any potential issues with serializers, I think this could be a Flink issue.

Steps to reproduce:

1. git clone https://github.com/mxm/beam
2. cd beam && git checkout savepoint-problem
3. ./gradlew :runners:flink:1.6:test --tests "**.FlinkSavepointTest.testSavepointRestoreLegacy"

Error:

java.lang.Exception: Exception while creating StreamOperatorStateContext.
	at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:192)
	at org.apache.flink.streaming.api.operators.AbstractStreamOperator.initializeState(AbstractStreamOperator.java:250)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.initializeState(StreamTask.java:738)
	at org.apache.flink.streaming.runtime.tasks.StreamTask.invoke(StreamTask.java:289)
	at org.apache.flink.runtime.taskmanager.Task.run(Task.java:711)
	at java.lang.Thread.run(Thread.java:745)
Caused by: org.apache.flink.util.FlinkException: Could not restore keyed state backend for DoFnOperator_76375152c4a81d5df72cf49e32c4ecb9_(4/4) from any of the 1 provided restore options.
	at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:137)
	at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.keyedStatedBackend(StreamTaskStateInitializerImpl.java:279)
	at org.apache.flink.streaming.api.operators.StreamTaskStateInitializerImpl.streamOperatorStateContext(StreamTaskStateInitializerImpl.java:133)
	... 5 more
Caused by: java.lang.RuntimeException: Invalid namespace string: ''
	at org.apache.beam.runners.core.StateNamespaces.fromString(StateNamespaces.java:245)
	at org.apache.beam.runners.core.TimerInternals$TimerDataCoder.decode(TimerInternals.java:246)
	at org.apache.beam.runners.core.TimerInternals$TimerDataCoder.decode(TimerInternals.java:221)
	at org.apache.beam.runners.flink.translation.types.CoderTypeSerializer.deserialize(CoderTypeSerializer.java:92)
	at org.apache.flink.streaming.api.operators.TimerSerializer.deserialize(TimerSerializer.java:169)
	at org.apache.flink.streaming.api.operators.TimerSerializer.deserialize(TimerSerializer.java:45)
	at org.apache.flink.runtime.state.KeyGroupPartitioner$PartitioningResultKeyGroupReader.readMappingsInKeyGroup(KeyGroupPartitioner.java:297)
	at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.readKeyGroupStateData(HeapKeyedStateBackend.java:513)
	at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.readStateHandleStateData(HeapKeyedStateBackend.java:474)
	at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restorePartitionedState(HeapKeyedStateBackend.java:431)
	at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restore(HeapKeyedStateBackend.java:370)
	at org.apache.flink.runtime.state.heap.HeapKeyedStateBackend.restore(HeapKeyedStateBackend.java:105)
	at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.attemptCreateAndRestore(BackendRestorerProcedure.java:151)
	at org.apache.flink.streaming.api.operators.BackendRestorerProcedure.createAndRestore(BackendRestorerProcedure.java:123)
	... 7 more

It is possible to change the maxParallelism to other values. The following lead to failure:

   options.setMaxParallelism(128); // default value
   options.setMaxParallelism(64);
    options.setMaxParallelism(118);

The following work fine:

    options.setMaxParallelism(110);
    options.setMaxParallelism(63);
    options.setMaxParallelism(24);

[1] https://github.com/apache/beam/commit/52d7291144f64eaa417862558d71a443fae3d690

Everything works fine with RocksDB.

Issue Links

• is related to: BEAM-7144 Job re-scale fails on Flink >= 1.6 with certain values of maxParallelism