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Posted to issues@flink.apache.org by tillrohrmann <gi...@git.apache.org> on 2017/05/18 11:46:25 UTC

[GitHub] flink pull request #3939: [FLINK-6612] Allow ZooKeeperStateHandleStore to lo...

GitHub user tillrohrmann opened a pull request:

    https://github.com/apache/flink/pull/3939

    [FLINK-6612] Allow ZooKeeperStateHandleStore to lock created ZNodes

    In order to guard against deletions of ZooKeeper nodes which are still being used
    by a different ZooKeeperStateHandleStore, we have to introduce a locking mechanism.
    Only after all ZooKeeperStateHandleStores have released their lock, the ZNode is
    allowed to be deleted.
    
    THe locking mechanism is implemented via ephemeral child nodes of the respective
    ZooKeeper node. Whenever a ZooKeeperStateHandleStore wants to lock a ZNode, thus,
    protecting it from being deleted, it creates an ephemeral child node. The node's
    name is unique to the ZooKeeperStateHandleStore instance. The delete operations
    will then only delete the node if it does not have any children associated.
    
    In order to guard against oprhaned lock nodes, they are created as ephemeral nodes.
    This means that they will be deleted by ZooKeeper once the connection of the
    ZooKeeper client which created the node timed out.
    
    cc @StefanRRichter


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

    $ git pull https://github.com/tillrohrmann/flink addZooKeeperRefCounting

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

    https://github.com/apache/flink/pull/3939.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 #3939
    
----
commit def077a8d95921645733169d420d548842dde257
Author: Till Rohrmann <tr...@apache.org>
Date:   2017-05-17T12:52:04Z

    [FLINK-6612] Allow ZooKeeperStateHandleStore to lock created ZNodes
    
    In order to guard against deletions of ZooKeeper nodes which are still being used
    by a different ZooKeeperStateHandleStore, we have to introduce a locking mechanism.
    Only after all ZooKeeperStateHandleStores have released their lock, the ZNode is
    allowed to be deleted.
    
    THe locking mechanism is implemented via ephemeral child nodes of the respective
    ZooKeeper node. Whenever a ZooKeeperStateHandleStore wants to lock a ZNode, thus,
    protecting it from being deleted, it creates an ephemeral child node. The node's
    name is unique to the ZooKeeperStateHandleStore instance. The delete operations
    will then only delete the node if it does not have any children associated.
    
    In order to guard against oprhaned lock nodes, they are created as ephemeral nodes.
    This means that they will be deleted by ZooKeeper once the connection of the
    ZooKeeper client which created the node timed out.

----


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[GitHub] flink pull request #3939: [FLINK-6612] Allow ZooKeeperStateHandleStore to lo...

Posted by tillrohrmann <gi...@git.apache.org>.
Github user tillrohrmann closed the pull request at:

    https://github.com/apache/flink/pull/3939


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[GitHub] flink issue #3939: [FLINK-6612] Allow ZooKeeperStateHandleStore to lock crea...

Posted by StefanRRichter <gi...@git.apache.org>.
Github user StefanRRichter commented on the issue:

    https://github.com/apache/flink/pull/3939
  
    LGMT +1. Tested that this is running with incremental checkpoints, however the test did not (yet) cover a "split brain" scenario with to JobManagers running in parallel.


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[GitHub] flink issue #3939: [FLINK-6612] Allow ZooKeeperStateHandleStore to lock crea...

Posted by StefanRRichter <gi...@git.apache.org>.
Github user StefanRRichter commented on the issue:

    https://github.com/apache/flink/pull/3939
  
    Thanks for your work @tillrohrmann ! I merged this manually. Please close this PR and the jira.


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[GitHub] flink issue #3939: [FLINK-6612] Allow ZooKeeperStateHandleStore to lock crea...

Posted by tillrohrmann <gi...@git.apache.org>.
Github user tillrohrmann commented on the issue:

    https://github.com/apache/flink/pull/3939
  
    Merged in 3d119e1155aa8930cc7b18a085d6790cb2c63b70


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