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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (FLINK-10185) Make ZooKeeperStateHandleStore#releaseAndTryRemove synchronous
Date Mon, 20 Aug 2018 22:42:00 GMT

    [ https://issues.apache.org/jira/browse/FLINK-10185?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16586610#comment-16586610
] 

ASF GitHub Bot commented on FLINK-10185:
----------------------------------------

tillrohrmann opened a new pull request #6586: [FLINK-10185] Make ZooKeeperStateHandleStore#releaseAndTryRemove
synchronous
URL: https://github.com/apache/flink/pull/6586
 
 
   ## What is the purpose of the change
   
   Remove the asynchronous callback from ZooKeeperStateHandleStore#releaseAndTryRemove.
   Instead we can execute the callback after having executed the releaseAndTryRemove
   method successfully. This separates concerns better because we don't mix storage
   with business logic. Furthermore, we can still avoid blocking operations if we use a
   separate thread to call into ZooKeeperStateHandleStore#releaseAndTryRemove.
   
   ## Brief change log
   
   - Make `ZooKeeperStateHandleStore#releaseAndTryRemove` synchronous
   - Introduce `ZooKeeperResource` which starts a `ZooKeeper` server
   
   ## Verifying this change
   
   - Changes is covered by `ZooKeeperStateHandleStoreTest#testRemove` and `ZooKeeperCompletedCheckpointStoreTest#testDiscardingSubsumedCheckpoints`
and `ZooKeeperCompletedCheckpointStoreTest#testDiscardingCheckpointsAtShutDown`
   
   ## Does this pull request potentially affect one of the following parts:
   
     - Dependencies (does it add or upgrade a dependency): (no)
     - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: (no)
     - The serializers: (no)
     - The runtime per-record code paths (performance sensitive): (no)
     - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing,
Yarn/Mesos, ZooKeeper: (yes)
     - The S3 file system connector: (no)
   
   ## Documentation
   
     - Does this pull request introduce a new feature? (no)
     - If yes, how is the feature documented? (not applicable)
   

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> Make ZooKeeperStateHandleStore#releaseAndTryRemove synchronous
> --------------------------------------------------------------
>
>                 Key: FLINK-10185
>                 URL: https://issues.apache.org/jira/browse/FLINK-10185
>             Project: Flink
>          Issue Type: Improvement
>          Components: Distributed Coordination
>    Affects Versions: 1.4.2, 1.5.2, 1.6.0, 1.7.0
>            Reporter: Till Rohrmann
>            Assignee: Till Rohrmann
>            Priority: Major
>              Labels: pull-request-available
>             Fix For: 1.4.3, 1.6.1, 1.7.0, 1.5.4
>
>
> The {{ZooKeeperStateHandleStore#releaseAndTryRemove}} method executes parts of its logic
synchronously (retrieving the state handle and unlocking the ZNode) and others asynchronously
(removing the ZNode). Moreover, the method takes a parameter which is used to execute some
logic in case of a successful removal. This was done in order to execute a potentially blocking
state discard operation in a different thread.
> I think this can be simplified by executing all logic in the same thread and running
the callback after having called {{ZooKeeperStateHandleStore#releaseAndTryRemove}}. Moreover,
if this operation needs to be not blocking one could use a different thread to call into this
method. 



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