[jira] [Commented] (FLINK-6869) Scala serializers do not have the serialVersionUID specified

["ASF GitHub Bot (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/FLINK-6869?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16042715#comment-16042715 ] 

ASF GitHub Bot commented on FLINK-6869:
---------------------------------------

GitHub user tzulitai opened a pull request:

    https://github.com/apache/flink/pull/4090

    [FLINK-6869] [scala] Specify serialVersionUID for all Scala serializers

    This PR fixes 2 issues:
    
    1. Configuration snapshots of Scala serializers were not readable:
    Prior to this PR, the configuration snapshot classes of Scala serializers did not have the proper default empty constructor that is used for deserializing the configuration snapshot.
    
    Since some Scala serializers' config snapshots extend the Java `CompositeTypeSerializerConfigSnapshot`, their config snapshot classes are also changed to be implemented in Java since in Scala we can only call a single base class constructor from subclasses.
    
    2. Scala serializers did not specify the serialVersionUID:
    Previously, Scala serializers did not specify the `serialVersionUID`, and therefore prohibited restore from previous Flink version snapshots because the serializers' implementations changed in 1.3.
    
    The `serialVersionUID`s added in this PR are identical to what they were (as generated by Java) in Flink 1.2, so that we can at least restore state that were written with the Scala serializers as of 1.2.


You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/tzulitai/flink FLINK-6869

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/flink/pull/4090.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #4090
    
----
commit 416bd3b122e79bdd8b5876e8d645b346110b67f0
Author: Tzu-Li (Gordon) Tai <tz...@apache.org>
Date:   2017-06-08T06:52:04Z

    [hotfix] [scala] Fix instantiation of Scala serializers' config snapshot classes
    
    Prior to this commit, the configuration snapshot classes of Scala
    serializers did not have the proper default empty constructor that is
    used for deserializing the configuration snapshot.
    
    Since some Scala serializers' config snapshots extend the Java
    CompositeTypeSerializerConfigSnapshot, their config snapshot classes are
    also changed to be implemented in Java since in Scala we can only call a
    single base class constructor from subclasses.

commit 16574c6623dd64846c888e6a608deb9ae3f081bd
Author: Tzu-Li (Gordon) Tai <tz...@apache.org>
Date:   2017-06-08T13:29:45Z

    [FLINK-6869] [scala] Specify serialVersionUID for all Scala serializers
    
    Previously, Scala serializers did not specify the serialVersionUID, and
    therefore prohibited restore from previous Flink version snapshots
    because the serializers' implementations changed.
    
    The serialVersionUIDs added in this commit are identical to what they
    were (as generated by Java) in Flink 1.2, so that we can at least
    restore state that were written with the Scala serializers as of 1.2.

----


> Scala serializers do not have the serialVersionUID specified
> ------------------------------------------------------------
>
>                 Key: FLINK-6869
>                 URL: https://issues.apache.org/jira/browse/FLINK-6869
>             Project: Flink
>          Issue Type: Bug
>          Components: Scala API, Type Serialization System
>    Affects Versions: 1.3.0
>            Reporter: Tzu-Li (Gordon) Tai
>            Assignee: Tzu-Li (Gordon) Tai
>            Priority: Blocker
>              Labels: flink-rel-1.3.1-blockers
>             Fix For: 1.3.1
>
>
> Currently, all Scala serializers, e.g. {{OptionSerializer}}, {{CaseClassSerializer}}, {{TrySerializer}} etc. do not have the serialVersionUID specified.
> In 1.3, the Scala serializer (all serializers in general) implementations had to be changed since implementation of the compatibility methods {{snapshotConfiguration}}, {{ensureCompatibility}} had to be implemented, resulting in a new serialVersionUID.
> This means that when restoring from a snapshot pre-1.3 that contains Scala types as state, the previous serializer in the snapshot cannot be deserialized (due to UID mismatch).
> To fix this, we should specify the serialVersionUIDs of the Scala serializers to be what they originally were pre-1.3. This would then allow users with Scala types as state to restore from older versions.



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