[jira] [Created] (FLINK-6944) Introduce DefaultTypeSerializerConfigSnapshot as a base implementation for serializer compatibility checks

["Tzu-Li (Gordon) Tai (JIRA)" <ji...@apache.org>]

Tzu-Li (Gordon) Tai created FLINK-6944:
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             Summary: Introduce DefaultTypeSerializerConfigSnapshot as a base implementation for serializer compatibility checks
                 Key: FLINK-6944
                 URL: https://issues.apache.org/jira/browse/FLINK-6944
             Project: Flink
          Issue Type: Improvement
          Components: State Backends, Checkpointing, Type Serialization System
    Affects Versions: 1.3.0, 1.3.1
            Reporter: Tzu-Li (Gordon) Tai
            Assignee: Tzu-Li (Gordon) Tai
             Fix For: 1.4.0


Currently, we store both the {{TypeSerializer}} and its corresponding {{TypeSerializerConfigSnapshot}} in checkpoints of managed state. This, in most cases, are actually duplicate information.

This JIRA proposes to change this by only storing the {{TypeSerializerConfigSnapshot}}, while at the same time, letting {{TypeSerializer.snapshotConfiguration}} return a default {{DefaultTypeSerializerConfigSnapshot}}.
This default simply serializes the serializer instance using Java serialization.

The {{DefaultTypeSerializerConfigSnapshot}} should wrap the serializer bytes, the serialVersionUID of the serializer class, and the serializer class' classname. The latter two will be used to check compatibility in the default implementation of {{TypeSerializer.ensureCompatibility}}. Specifically, if classname / serialVersionUID has changed, the default implementation of {{TypeSerializer.ensureCompatibility}} will simply return {{CompatibilityResult.requiresMigration}} with the deserialized serializer as the convert deserializer.



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