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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-2713) Custom StateCheckpointers should be included in the snapshots
Date Sun, 20 Sep 2015 06:44:04 GMT

    [ https://issues.apache.org/jira/browse/FLINK-2713?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14877445#comment-14877445
] 

ASF GitHub Bot commented on FLINK-2713:
---------------------------------------

GitHub user gyfora opened a pull request:

    https://github.com/apache/flink/pull/1150

    [FLINK-2713] [streaming] Include custom StateCheckpointers in the snapshots

    Currently failure recovery fails when using custom StateCheckpointers because they are
not correctly set before trying to restore the operator initial state. This PR solves this
issue by including custom StateCheckpointers in the snapshot.
    
    The current order of events and the problem:
     1. Create StreamTask
     2. Call restoreInitialState(snapshot) -> default java-serialization StateCheckpointer
is used
     3. Open UDF and run computation. -> This is the point when custom StateCheckpointers
are set
     4. Take snapshots....
    
    We can see while the custom StateCheckpointers are available and work for taking snapshots
they are not set set yet when call restore which obviously leads to error.
    
    This PR now includes the custom StateCheckpointer in the snapshot so we can set it in
step 2. before calling restore. An optimization is that we include only the serialized version
as a byte array in the buffer so we don't need to serialize it over and over again.
    
    The PR also extends the StreamCheckpointingITCase and the PartitionedStateCheckpointingITCase
to include a case for custom StateCheckpointers for both local and partitioned OperatorStates.

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

    $ git pull https://github.com/gyfora/flink checkpointer

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

    https://github.com/apache/flink/pull/1150.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 #1150
    
----
commit ca8c04899554c0d438154b5eefc3e8e6b5543888
Author: Gyula Fora <gyfora@apache.org>
Date:   2015-09-19T19:35:07Z

    [FLINK-2713] [streaming] Include custom StateCheckpointers in the snapshots

----


> Custom StateCheckpointers should be included in the snapshots
> -------------------------------------------------------------
>
>                 Key: FLINK-2713
>                 URL: https://issues.apache.org/jira/browse/FLINK-2713
>             Project: Flink
>          Issue Type: Bug
>          Components: Streaming
>            Reporter: Gyula Fora
>            Assignee: Gyula Fora
>
> Currently the restoreInitialState call fails when the user uses a custom StateCheckpointer
to create the snapshot, because the state is restored before the StateCheckpointer is set
for the StreamOperatorState. (because the restoreInitialState() call precedes the open() call)
> To avoid this issue, the custom StateCheckpointer instance should be stored within the
snapshot and should be set in the StreamOperatorState before calling restoreState(..).
> To reduce the overhead induced by this we can do 2 optimizations:
>  - We only include custom StateCheckpointers (the default java serializer one is always
available)
>  - We only serialize the checkpointer once and store the byte array in the snapshot



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