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https://issues.apache.org/jira/browse/SPARK-46182?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Dongjoon Hyun closed SPARK-46182.
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> Shuffle data lost on decommissioned executor caused by race condition between
> lastTaskRunningTime and lastShuffleMigrationTime
> ------------------------------------------------------------------------------------------------------------------------------
>
> Key: SPARK-46182
> URL: https://issues.apache.org/jira/browse/SPARK-46182
> Project: Spark
> Issue Type: Task
> Components: Spark Core
> Affects Versions: 3.4.1, 3.5.0
> Reporter: Xingbo Jiang
> Assignee: Xingbo Jiang
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.5.1, 3.4.3, 4.0.0
>
>
> We recently identified a very tricky race condition in decommissioned node,
> which could lead to shuffle data lost even data migration is enabled:
> * At 04:30:51, RDD block refresh happened, and found no pending works
> * Shortly after that (a few milliseconds), the shutdownThread in
> CoarseGrainedExecutorBackend found 1 running task, so lastTaskRunningTime
> updated to the current system nano time
> * Shortly after that, Shuffle block refresh happened, and found no pending
> works
> * Shortly after that, a task finished on the decommissioned executor, and
> generated new shuffle blocks
> * One second later, the shutdownThread in CoarseGrainedExecutorBackend found
> no running task, lastTaskRunningTime would not be updated, and the executor
> didn’t exit because min(lastRDDMigrationTime, lastShuffleMigrationTime) <
> lastTaskRunningTime
> * After 30 seconds, at 04:31:21, RDD block refresh happened, and found no
> pending works, lastRDDMigrationTime updated to the current system nano time
> * At this exact moment, all known blocks are migrated, and
> min(lastRDDMigrationTime, lastShuffleMigrationTime) > lastTaskRunningTime
> * shutdownThread is triggered, and asked to stop the executor
> * Shuffle block refresh thread was still sleeping, and got interrupted by the
> stop command, so it didn’t have the chance to discover the shuffle blocks
> generated by the previously finished task
> * Eventually, the executor exited, and the output of the task was lost, Spark
> need to recompute that partition
> The root cause for the race condition is that the Shuffle block refresh
> happened between lastTaskRunningTime was updated and task finished, in that
> case the shutdownThread could request to stop the executor before the
> BlockManagerDecommissioner discover the new shuffle blocks generated by the
> latest finished task.
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