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https://issues.apache.org/jira/browse/FLINK-6612?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16017172#comment-16017172
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ASF GitHub Bot commented on FLINK-6612:
---------------------------------------
Github user tillrohrmann commented on the issue:
https://github.com/apache/flink/pull/3939
Merged in 3d119e1155aa8930cc7b18a085d6790cb2c63b70
> ZooKeeperStateHandleStore does not guard against concurrent delete operations
> -----------------------------------------------------------------------------
>
> Key: FLINK-6612
> URL: https://issues.apache.org/jira/browse/FLINK-6612
> Project: Flink
> Issue Type: Bug
> Components: Distributed Coordination, State Backends, Checkpointing
> Affects Versions: 1.3.0, 1.4.0
> Reporter: Till Rohrmann
> Assignee: Till Rohrmann
> Priority: Blocker
> Fix For: 1.3.0, 1.4.0
>
>
> The {{ZooKeeperStateHandleStore}} does not guard against concurrent delete
> operations which could happen in case of a lost leadership and a new
> leadership grant. The problem is that checkpoint nodes can get deleted even
> after they have been recovered by another
> {{ZooKeeperCompletedCheckpointStore}}. This corrupts the recovered checkpoint
> and thwarts future recoveries.
> I propose to add reference counting to the {{ZooKeeperStateHandleStore}}.
> That way, we can monitor how many concurrent processes have a hold on a given
> checkpoint node. Only if the reference count reaches {{0}}, we are allowed to
> delete the checkpoint node and dispose the checkpoint data.
> Stephan proposed to use ephemeral child nodes to track the reference count of
> a checkpoint node. That way we are sure that locks on the a checkpoint node
> are released in case of {{JobManager}} failures.
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