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https://issues.apache.org/jira/browse/FLINK-6353?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15996707#comment-15996707
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Aljoscha Krettek commented on FLINK-6353:
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It does work now, yes, with the process outlined in the description. I left it
open because we might want to implement [~srichter]'s idea to simplify the
migration process. We can open a separate issue for that, though.
> Restoring using CheckpointedRestoring does not work from 1.2 to 1.2
> -------------------------------------------------------------------
>
> Key: FLINK-6353
> URL: https://issues.apache.org/jira/browse/FLINK-6353
> Project: Flink
> Issue Type: Bug
> Components: DataStream API, State Backends, Checkpointing
> Affects Versions: 1.2.0, 1.2.1
> Reporter: Aljoscha Krettek
> Assignee: Aljoscha Krettek
>
> State that was checkpointed using {{Checkpointed}} (on a user function)
> cannot be restored using {{CheckpointedRestoring}} when the savepoint was
> done on Flink 1.2. The reason is an overzealous check in
> {{AbstractUdfStreamOperator}} that only restores from "legacy" operator state
> using {{CheckpointedRestoring}} when the stream is a {{Migration}} stream.
> We can remove that check but still need to make sure to read away the byte
> that indicates whether there is legacy state, which is written when we're
> restoring from a Flink 1.1 savepoint.
> Also, if we remove the check, the procedure for a user to migrate a user
> function away from the {{Checkpointed}} interface is this:
> # Perform savepoint with user function still implementing {{Checkpointed}},
> shutdown job
> # Change user function to implement {{CheckpointedRestoring}}
> # Restore from previous savepoint, user function has to somehow move the
> state that is restored using {{CheckpointedRestoring}} to another type of
> state, .e.g operator state, using the {{OperatorStateStore}}.
> # Perform another savepoint, shutdown job
> # Remove {{CheckpointedRestoring}} interface from user function
> # Restore from the second savepoint
> # Done.
> If the {{CheckpointedRestoring}} interface is not removed as prescribed in
> the last steps then a future restore of a new savepoint will fail because
> Flink will try to read legacy operator state that is not there anymore.
> The above steps also apply to Flink 1.3, when a user want's to move away from
> the {{Checkpointed}} interface.
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