[GitHub] [helix] alirezazamani commented on issue #461: Investigate FixedTargetTaskAssignmentCalculator

[GitBox <gi...@apache.org>]

alirezazamani commented on issue #461: Investigate FixedTargetTaskAssignmentCalculator
URL: https://github.com/apache/helix/issues/461#issuecomment-539685233
 
 
   Here is the outcome of the investigation on FixedTargetedTasks:
   1- These tasks will be assigned to the instances based on the on the outcome of the class:FixedTargetTaskAssignmentCalculator -> function:computeAssignmentAndChargeResource.
   
   2- In the function:updatePreviousAssignedTasksStatus of the class:AbstractTaskDispatcher, whenever currentState is INIT (currentState==INIT or (currentState==null and Context==INIT) or (currentState==null and Context==null)), this partition will be added to assignedPartitions and will be excluded from being assignment in the method mentioned in Step1. In conclusion, whenever this task is targeted task, it makes sense to not take any decision about this task and let the FixedTargetTaskAssignmentCalculator to decide on the new assignment of the targeted task.
   
   3- However, for the cases where current state is actually INIT, we might not have any assignment, because in function:computeAssignmentAndChargeResource, line 260: in condition "prevInstance.equals(instance)", we break and there won't be any assignment. As a result, this break should be removed which allows this function to take new decision for the tasks.
   
   4- Finally, with these changes, One of the tests will fails. This test is called TestTaskNumAttempts.
   The reason is potentially related to pending messages and race condition that can happen when there is pending message for the tasks.
   
   5- More investigation is needed.

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