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  1. Spark
  2. SPARK-24909

Spark scheduler can hang when fetch failures, executor lost, task running on lost executor, and multiple stage attempts

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Details

    • Bug
    • Status: Resolved
    • Critical
    • Resolution: Fixed
    • 2.3.1
    • 2.3.2, 2.4.0
    • Scheduler, Spark Core
    • None

    Description

      The DAGScheduler can hang if the executor was lost (due to fetch failure) and all the tasks in the tasks sets are marked as completed. (https://github.com/apache/spark/blob/master/core/src/main/scala/org/apache/spark/scheduler/DAGScheduler.scala#L1265)

      It never creates new task attempts in the task scheduler but the dag scheduler still has pendingPartitions.

      8/07/22 08:30:00 INFO scheduler.TaskSetManager: Starting task 55769.0 in stage 44.0 (TID 970752, host1.com, executor 33, partition 55769, PROCESS_LOCAL, 7874 bytes)
      
      18/07/22 08:30:29 INFO scheduler.DAGScheduler: Marking ShuffleMapStage 44 (repartition at Lift.scala:191) as failed due to a fetch failure from ShuffleMapStage 42 (map at foo.scala:27)
      18/07/22 08:30:29 INFO scheduler.DAGScheduler: Resubmitting ShuffleMapStage 42 (map at foo.scala:27) and ShuffleMapStage 44 (repartition at bar.scala:191) due to fetch failure
      ....
      
      18/07/22 08:30:56 INFO scheduler.DAGScheduler: Executor lost: 33 (epoch 18)
      18/07/22 08:30:56 INFO schedulerDAGScheduler: Shuffle files lost for executor: 33 (epoch 18)
      
      18/07/22 08:31:20 INFO scheduler.DAGScheduler: Submitting ShuffleMapStage 44 (MapPartitionsRDD[70] at repartition at bar.scala:191), which has no missing parents
      18/07/22 08:31:21 INFO cluster.YarnClusterScheduler: Adding task set 44.1 with 59955 tasks
      
      18/07/22 08:31:41 INFO scheduler.TaskSetManager: Finished task 55769.0 in stage 44.0 (TID 970752) in 101505 ms on host1.com (executor 33) (15081/73320)
      
      8/07/22 08:31:41 INFO scheduler.DAGScheduler: Ignoring possibly bogus ShuffleMapTask(44, 55769) completion from executor 33

       

      In the logs above you will see that task 55769.0 finished after the executor was lost and a new task set was started.  The DAG scheduler says "Ignoring possibly bogus".. but in the TaskSetManager side it has marked those tasks as completed for all stage attempts. The DAGScheduler gets hung here.  I did a heap dump on the process and can see that 55769 is still in the DAGScheduler pendingPartitions list but the tasksetmanagers are all complete

      Note to reproduce this, you need a situation where  you have a shufflemaptask (call it task1) fetching data from an executor where it also has other shufflemaptasks (call it task2) running (fetch from other hosts). the task1 fetching the data has to FetchFail which would cause the stage to fail and the executor to be marked as lost due to the fetch failure.  It restarts a new task set for the new stage attempt, then the shufflemaptask task2 that was running on the executor that was marked Lost finished.  The scheduler ignore that complete event  "Ignoring possible bogus ...". This results in a hang because at this point the TaskSetManager has already marked all tasks for all attempts of that stage as completed.

       

      Configs needed to be on:

      spark.blacklist.application.fetchFailure.enabled=true  
      spark.blacklist.application.fetchFailure.enabled=true

      spark.files.fetchFailure.unRegisterOutputOnHost=true

      spark.shuffle.service.enabled=true

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              tgraves Thomas Graves
              tgraves Thomas Graves
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