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https://issues.apache.org/jira/browse/FLINK-23143?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17524708#comment-17524708
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Hangxiang Yu commented on FLINK-23143:
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Hi, [~roman].
IIUC, we need to create and maintain a new state in
_ChangelogKeyedStateBackend_ in your solution ?
It may not work well in the case of switching changelog from enabled to
disabled ?
Another solution is to make changelog part use correct
_RegisteredKeyValueStateBackendMetaInfo/RegisteredPriorityQueueStateBackendMetaInfo_
when recovery.
(We create
_RegisteredKeyValueStateBackendMetaInfo/RegisteredPriorityQueueStateBackendMetaInfo_
with _StateMetaInfoSnapshot_ in
_ChangelogBackendLogApplier#restoreKvMetaData_ and
_ChangelogBackendLogApplier#restorePqMetaData_ but not use them)
But two new methods may be introduced in
{_}KeyedStateBackend{_}.e.g.{_}create(RegisteredPriorityQueueStateBackendMetaInfo
metaInfo).{_}
I have tried to do a simple POC and it works. But it may not be a good idea to
introduce some new methods in _KeyedStateBackend._
WDYT?
> Support state migration
> -----------------------
>
> Key: FLINK-23143
> URL: https://issues.apache.org/jira/browse/FLINK-23143
> Project: Flink
> Issue Type: Sub-task
> Components: Runtime / State Backends
> Reporter: Roman Khachatryan
> Priority: Minor
> Fix For: 1.16.0
>
>
> ChangelogKeyedStateBackend.getOrCreateKeyedState is currently used during
> recovery; on 1st user access, it doesn't update metadata nor migrate state
> (as opposed to other backends).
>
> The proposed solution is to
> # wrap serializers (and maybe other objects) in getOrCreateKeyedState
> # store wrapping objects in a new map keyed by state name
> # pass wrapped objects to delegatedBackend.createInternalState
> # on 1st user access, lookup wrapper and upgrade its wrapped serializer
> This should be done for both KV/PQ states.
>
> See also [https://github.com/apache/flink/pull/15420#discussion_r656934791]
>
> cc: [~yunta]
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