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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-9377) Remove writing serializers as part of the checkpoint meta information
Date Mon, 08 Oct 2018 11:11:01 GMT

    [ https://issues.apache.org/jira/browse/FLINK-9377?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16641668#comment-16641668

ASF GitHub Bot commented on FLINK-9377:

dawidwys commented on a change in pull request #6711: [FLINK-9377] [core, state backends]
Remove serializers from checkpoints
URL: https://github.com/apache/flink/pull/6711#discussion_r223321240

 File path: flink-runtime/src/main/java/org/apache/flink/runtime/state/OperatorBackendSerializationProxy.java
 @@ -38,7 +40,16 @@
 public class OperatorBackendSerializationProxy extends VersionedIOReadableWritable {
-	public static final int VERSION = 4;
+	public static final int VERSION = 5;
+	private static final Map<Integer, Integer> META_INFO_SNAPSHOT_FORMAT_VERSION_MAPPER
= new HashMap<>();
+	static {
 Review comment:
   I found this mapping particularly hard to understand. I could not figure out any better
way so far though. Anyway I think we should have it in mind to revisit this mapping.

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> Remove writing serializers as part of the checkpoint meta information
> ---------------------------------------------------------------------
>                 Key: FLINK-9377
>                 URL: https://issues.apache.org/jira/browse/FLINK-9377
>             Project: Flink
>          Issue Type: Sub-task
>          Components: State Backends, Checkpointing
>            Reporter: Tzu-Li (Gordon) Tai
>            Assignee: Tzu-Li (Gordon) Tai
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 1.7.0
> When writing meta information of a state in savepoints, we currently write both the state
serializer as well as the state serializer's configuration snapshot.
> Writing both is actually redundant, as most of the time they have identical information.
>  Moreover, the fact that we use Java serialization to write the serializer and rely on
it to be re-readable on the restore run, already poses problems for serializers such as the
{{AvroSerializer}} (see discussion in FLINK-9202) to perform even a compatible upgrade.
> The proposal here is to leave only the config snapshot as meta information, and use that
as the single source of truth of information about the schema of serialized state.
>  The config snapshot should be treated as a factory (or provided to a factory) to re-create
serializers capable of reading old, serialized state.

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