Myasuka opened a new pull request #7711: [FLINK-11618][state] Refactor operator state repartition mechanism URL: https://github.com/apache/flink/pull/7711 ## What is the purpose of the change There existed two problems during state assignment when parallelism not changed: 1. If we only have even-split redistributed state, current implementation actually cannot ensure state assignment to keep as the same as previously. This is because current `StateAssignmentOperation#collectPartitionableStates` would repartition managedOperatorStates without subtask-index information. Take an example, if we have a operator-state with parallelism as 2, and subtask-0's managed-operatorstate is empty while subtask-1 not. Although new parallelism still keeps as 2, after `StateAssignmentOperation#collectPartitionableStates` and state assigned, subtask-0 would be assigned the managed-operatorstate while subtask-1 got none. 1. We should only redistribute union state and not touch the even-split state. Redistribute even-split state would cause unexpected behavior after `RestartPipelinedRegionStrategy` supported to restore state. This PR will fix the above two problems. ## Brief change log - Refactor `StateAssignmentOperation#collectPartitionableStates` to let returned `managedOperatorStates` has subtask-index information. - Refactor API of `OperatorStateRepartitioner` and its implementation `RoundRobinOperatorStateRepartitioner`. The logical of comparing old and new parallelism is now located in `OperatorStateRepartitioner#repartitionState`. - Refactor `AbstractStreamOperatorTestHarness` to extract the logic of repartitioning operator state into a new method `AbstractStreamOperatorTestHarness#repartitionOperatorState` instead of previously contained in `AbstractStreamOperatorTestHarness#initializeState`. ## Verifying this change This change added tests and can be verified as follows: - Added `StateAssignmentOperationTest` to verify the logic of `StateAssignmentOperation#reDistributePartitionableStates`. - Existed all tests using `AbstractStreamOperatorTestHarness` could verify the refactor of `StateAssignmentOperation` generate the expected results as before. ## Does this pull request potentially affect one of the following parts: - Dependencies (does it add or upgrade a dependency): no - The public API, i.e., is any changed class annotated with `@Public(Evolving)`: no - The serializers: no - The runtime per-record code paths (performance sensitive): no - Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Yarn/Mesos, ZooKeeper: yes, this could affect state assignment when restoring checkpoint - The S3 file system connector: no ## Documentation - Does this pull request introduce a new feature? no - If yes, how is the feature documented? not applicable, this is a internal implementation, current doc should be enough.
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