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https://issues.apache.org/jira/browse/FLINK-8715?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16406943#comment-16406943
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Stephan Ewen commented on FLINK-8715:
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[~aljoscha] I think you are right, the problem is potentially deeper.
All parts of the code that obtain a serializer from a state descriptor need to
obey reconfiguration based on the serializer config snapshot. At least all
parts that touch data serialized by earlier versions. That includes queryable
state!
I think the best way to fix this (long run) would be to simply never have to
use the old serializer again. If there is a change between the serializers,
convert on restore, then the new serializer is safe to use. Everything else
seems like a deep rabbit hole.
The only worthwhile exception to this is may be Kryo, when the tag-to-class
mapping changes. Then we really want the new serializer to re-configure and not
convert the entire data set.
If we really want to handle that, then we would indeed have to either
- reconfigure the state descriptors
- or never/nowhere use the state descriptors internally (for default values,
etc.) but always use serializers/suppliers/etc obtained from the state
descriptors.
> RocksDB does not propagate reconfiguration of serializer to the states
> ----------------------------------------------------------------------
>
> Key: FLINK-8715
> URL: https://issues.apache.org/jira/browse/FLINK-8715
> Project: Flink
> Issue Type: Bug
> Components: State Backends, Checkpointing
> Affects Versions: 1.3.2
> Reporter: Arvid Heise
> Priority: Blocker
> Fix For: 1.5.0
>
>
> Any changes to the serializer done in #ensureCompability are lost during the
> state creation.
> In particular,
> [https://github.com/apache/flink/blob/master/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBValueState.java#L68]
> always uses a fresh copy of the StateDescriptor.
> An easy fix is to pass the reconfigured serializer as an additional parameter
> in
> [https://github.com/apache/flink/blob/master/flink-state-backends/flink-statebackend-rocksdb/src/main/java/org/apache/flink/contrib/streaming/state/RocksDBKeyedStateBackend.java#L1681]
> , which can be retrieved through the side-output of getColumnFamily
> {code:java}
> kvStateInformation.get(stateDesc.getName()).f1.getStateSerializer()
> {code}
> I encountered it in 1.3.2 but the code in the master seems unchanged (hence
> the pointer into master). I encountered it in ValueState, but I suspect the
> same issue can be observed for all kinds of RocksDB states.
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