[jira] [Created] (FLINK-24005) Resource requirements declaration may be incorrect if JobMaster disconnects with a TaskManager with available slots in the SlotPool

["Zhu Zhu (Jira)" <ji...@apache.org>]

Zhu Zhu created FLINK-24005:
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             Summary: Resource requirements declaration may be incorrect if JobMaster disconnects with a TaskManager with available slots in the SlotPool
                 Key: FLINK-24005
                 URL: https://issues.apache.org/jira/browse/FLINK-24005
             Project: Flink
          Issue Type: Bug
          Components: Runtime / Coordination
    Affects Versions: 1.13.2, 1.12.5, 1.14.0
            Reporter: Zhu Zhu


When a TaskManager disconnects with JobMaster, it will trigger the `DeclarativeSlotPoolService#decreaseResourceRequirementsBy()` for all the slots that are registered to the JobMaster from the TaskManager. If the slots are still available, i.e. not assigned to any task,  the `decreaseResourceRequirementsBy` may lead to incorrect resource requirements declaration.

For example, there is one job with 3 source tasks only. It requires 3 slots and declares for 3 slots. Initially all the tasks are running. Suddenly one task failed and waits for some delay before restarting. The previous slot is returned to the SlotPool. Now the job requires 2 slots and declares for 2 slots. At this moment, the TaskManager of that returned slot get lost. After the triggered `decreaseResourceRequirementsBy`, the job only declares for 1 slot. Finally, when the failed task starts to re-schedule, the job will declare for 2 slots while it actually needs 3 slots.

The attached log of a real job and logs of the added test in https://github.com/zhuzhurk/flink/commit/59ca0ac5fa9c77b97c6e8a43dcc53ca8a0ad6c37 can demonstrate this case.
Note that the real job is configured with a large "restart-strategy.fixed-delay.delay" and and large "slot.idle.timeout". So possibly in production it is a rare case.




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