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https://issues.apache.org/jira/browse/FLINK-25872?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17534913#comment-17534913
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Yuan Mei commented on FLINK-25872:
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I think [~dwysakowicz] and [~pnowojski] make a good point.
If we take changelog as a different state backend, it makes sense to follow the
current way of switching state backend through savepoints.
However, I think changelog is a bit different from the regular backend, I'd
instead take it as a different checkpoint type, similar to an unaligned
checkpoint, conceptually, but implemented in the state backend wrapper. That
says it provides the same format as the changelog checkpoint (changelog +
materialization) vs the unaligned checkpoint (channel data + snapshot).
The other part is that you do not expect to switch between hashmap <-> rocksDB
that often (most of the time, stick to just one). But on the other hand, enable
<=> disable changelog is reasonable to be more lightweight based on the
tradeoff between cp speed vs additional space/network cost.
> Restoring from non-changelog checkpoint with changelog state-backend enabled
> in CLAIM mode discards state in use
> ----------------------------------------------------------------------------------------------------------------
>
> Key: FLINK-25872
> URL: https://issues.apache.org/jira/browse/FLINK-25872
> Project: Flink
> Issue Type: Bug
> Components: Runtime / Checkpointing, Runtime / State Backends
> Reporter: Yun Tang
> Assignee: Yanfei Lei
> Priority: Major
> Labels: pull-request-available
> Fix For: 1.16.0
>
>
> If we restore from checkpoint with changelog state-backend enabled in
> snapshot CLAIM mode, the restored checkpoint would be discarded on subsume.
> This invalidates newer/active checkpoints because their materialized part is
> discarded (for incremental wrapped checkpoints, their private state is
> discarded). This bug is like FLINK-25478.
>
> Design doc:
> [https://docs.google.com/document/d/1KSFWc0gL7HkhC-JNrnsp06TLnsTmZOTHITQDcGMo0cI/edit?usp=sharing,]
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