[jira] [Closed] (FLINK-6612) ZooKeeperStateHandleStore does not guard against concurrent delete operations

["Till Rohrmann (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-6612?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Till Rohrmann closed FLINK-6612.
--------------------------------
    Resolution: Fixed

1.4.0: 3d119e1155aa8930cc7b18a085d6790cb2c63b70
1.3.0: f58fec70fef12056bd58b6cc2985532ccb07625e

> 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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