[jira] [Resolved] (FLINK-6190) Write "Serializer Configurations" metainfo along with state

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

     [ https://issues.apache.org/jira/browse/FLINK-6190?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Tzu-Li (Gordon) Tai resolved FLINK-6190.
----------------------------------------
    Resolution: Fixed

Merged for 1.3.0 with https://git-wip-us.apache.org/repos/asf/flink/commit/63c04a5

> Write "Serializer Configurations" metainfo along with state
> -----------------------------------------------------------
>
>                 Key: FLINK-6190
>                 URL: https://issues.apache.org/jira/browse/FLINK-6190
>             Project: Flink
>          Issue Type: Sub-task
>          Components: State Backends, Checkpointing, Type Serialization System
>            Reporter: Tzu-Li (Gordon) Tai
>            Assignee: Tzu-Li (Gordon) Tai
>
> In order for serializers to be able to be reconfigured on restore, we need knowledge of the previous serializer configurations, e.g. what types were registered, with which specific / default serializers, and especially for Kryo, the order they were registered.
> For this, we will need serializer configuration metainfo to be self-contained within the written state.
> For the implementation, we propose to include the following changes:
> - Have a new separate {{SerializersConfig}} class that is extracted from {{ExecutionConfig}}. This new class should contain only the serializer-related configurations (e.g., {{registeredKryoTypes}}, {{registeredPojoTypes}}, etc.). The {{SerializersConfig}} class should only be internally used, and therefore annotated with {{Internal}}. Users should still use the {{ExecutionConfig}} to configure serializers.
> - For serializers that previously require a {{ExecutionConfig}} in constructors, try changing them to take a {{SerializersConfig}} instead.
> - Introduce {{SerializersConfigSerializationProxy}}, which is in charge of serializing the current {{SerializersConfig}} when writing state to streams. This proxy defines the the serialized format of serializer configurations, therefore should  be a {{VersionedIOReadableWritable}} as we may change the format / information written in the future.
> - Add {{SerializersConfigSerializationProxy}} into state backends serialization proxies (e.g. {{KeyedBackendSerializationProxy}}) so that the serializer configuration is written into state. Need to additionally make sure backwards compatibility of previous-version backend serialization proxies.
> For the initial version, we propose to include the following within the written serialization config metadata (ordered):
> 1. {{registeredPojoTypes}}
> 2. {{Throwable.class}} --> {{org.apache.flink.api.java.typeutils.runtime.kryo.JavaSerializer}} default Flink-specific registry for serializing throwables.
> 3. {{defaultKryoSerializers}}
> 4. {{defaultKryoSerializerClasses}}
> 5. Kryo registrations for all primitive types (and boxed versions). This is to allow compatibility in case the built-in registrations for the primitive types change in Kryo in the future.
> 6. {{registeredTypesWithKryoSerializers}}
> 7. {{registeredTypesWithKryoSerializerClasses}}



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