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https://issues.apache.org/jira/browse/SPARK-18981?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sean Owen resolved SPARK-18981.
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Resolution: Won't Fix
> The last job hung when speculation is on
> ----------------------------------------
>
> Key: SPARK-18981
> URL: https://issues.apache.org/jira/browse/SPARK-18981
> Project: Spark
> Issue Type: Bug
> Components: Spark Core
> Affects Versions: 2.0.2
> Environment: spark2.0.2
> hadoop2.5.0
> Reporter: roncenzhao
> Priority: Critical
> Attachments: job_hang.png, run_scala.sh, Test.scala
>
>
> CONF:
> spark.speculation true
> spark.dynamicAllocation.minExecutors 0
> spark.executor.cores 2
> When I run the follow app, the bug will trigger.
> ```
> sc.runJob(job1)
> sleep(100s)
> sc.runJob(job2) // the job2 will hang and never be scheduled
> ```
> The triggering condition is described as follows:
> condition1: During the sleeping time, the executors will be released and the
> # of the executor will be zero some seconds later. The #numExecutorsTarget in
> 'ExecutorAllocationManager' will be 0.
> condition2: In 'ExecutorAllocationListener.onTaskEnd()', the numRunningTasks
> will be negative during the ending of job1's tasks.
> condition3: The job2 only hava one task.
> result:
> In the method 'ExecutorAllocationManager.updateAndSyncNumExecutorsTarget()',
> we will calculate #maxNeeded in 'maxNumExecutorsNeeded()'. Obviously,
> #numRunningOrPendingTasks will be negative and the #maxNeeded will be 0 or
> negative. So the 'ExecutorAllocationManager' will not request container from
> yarn. The app will hang.
> In the attachments, submitting the app by 'run_scala.sh' will lead to the
> 'hang' problem as the 'job_hang.png' shows.
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