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[jira] [Created] (FLINK-10255) Standby Dispatcher locks submitted JobGraphs


Till Rohrmann created FLINK-10255:
-------------------------------------

             Summary: Standby Dispatcher locks submitted JobGraphs
                 Key: FLINK-10255
                 URL: https://issues.apache.org/jira/browse/FLINK-10255
             Project: Flink
          Issue Type: Bug
          Components: Distributed Coordination
    Affects Versions: 1.6.0, 1.5.3, 1.7.0
            Reporter: Till Rohrmann
             Fix For: 1.6.1, 1.7.0, 1.5.4


Currently, standby {{Dispatchers}} lock submitted {{JobGraphs}} which are added to the {{SubmittedJobGraphStore}} if HA mode is enabled. Locking the {{JobGraphs}} can prevent their cleanup leaving the system in an inconsistent state.

The problem is that we recover in the {{SubmittedJobGraphListener#onAddedJobGraph}} callback which is also called if don't have the leadership the newly added {{JobGraph}}. Recovering the {{JobGraph}} currently locks the {{JobGraph}}. In case that the {{Dispatcher}} is not the leader, then we won't start that job after its recovery. However, we also don't release the {{JobGraph}} leaving it locked.

There are two possible solutions to the problem. Either we check whether we are the leader before recovering jobs or we say that recovering jobs does not lock them. Only if we can submit the recovered job we lock them. The latter approach has the advantage that it follows a quite similar code path as an initial job submission. Moreover, jobs are currently also recovered at other places. In all these places we currently would need to release the {{JobGraphs}} if we cannot submit the recovered {{JobGraph}} (e.g. {{Dispatcher#grantLeadership}}).

An extension of the first solution could be to stop the {{SubmittedJobGraphStore}} while the {{Dispatcher}} is not the leader. Then we would have to make sure that no concurrent callback from the {{SubmittedJobGraphStore#SubmittedJobGraphListener}} can be executed after revoking leadership from the {{Dispatcher}}.



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