Tzu-Li (Gordon) Tai created FLINK-8421:
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Summary: HeapInternalTimerService should reconfigure compatible
key / namespace serializers on restore
Key: FLINK-8421
URL: https://issues.apache.org/jira/browse/FLINK-8421
Project: Flink
Issue Type: Bug
Affects Versions: 1.4.0, 1.5.0
Reporter: Tzu-Li (Gordon) Tai
Priority: Blocker
Fix For: 1.3.3, 1.5.0, 1.4.1
The {{HeapInternalTimerService}} still uses simple {{equals}} checks on
restored / newly provided serializers for compatibility checks. This should be
replaced with the {{TypeSerializer::ensureCompatibility}} checks instead, so
that new serializers can be reconfigured.
For Flink 1.4.0 release and current master, this is a critical bug since the
{{KryoSerializer}} has different default base registrations than before due to
FLINK-7420. i.e if the key of a window is serialized using the
{{KryoSerializer}} in 1.3.x, the restore would never succeed in 1.4.0.
For 1.3.x, this fix would be an improvement, such that the
{{HeapInternalTimerService}} restore will make use of serializer
reconfiguration.
Other remarks:
* We need to double check all operators that checkpoint / restore from **raw**
state. Apparently, the serializer compatibility checks were only implemented
for managed state.
* Migration ITCases apparently do not have enough coverage. A migration test
job that uses a key type which required the {{KryoSerializer}}, and uses
windows, would have caught this issue.
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