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https://issues.apache.org/jira/browse/FLINK-6190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16000018#comment-16000018
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ASF GitHub Bot commented on FLINK-6190:
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Github user asfgit closed the pull request at:
https://github.com/apache/flink/pull/3804
> 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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