[jira] [Created] (SPARK-12755) Spark may attempt to rebuild application UI before finishing writing the event logs in possible race condition

["Michael Allman (JIRA)" <ji...@apache.org>]

Michael Allman created SPARK-12755:
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             Summary: Spark may attempt to rebuild application UI before finishing writing the event logs in possible race condition
                 Key: SPARK-12755
                 URL: https://issues.apache.org/jira/browse/SPARK-12755
             Project: Spark
          Issue Type: Bug
          Components: Spark Core
    Affects Versions: 1.5.2
            Reporter: Michael Allman
            Priority: Minor


As reported in SPARK-6950, it appears that sometimes the standalone master attempts to build an application's historical UI before closing the app's event log. This is still an issue for us in 1.5.2+, and I believe I've found the underlying cause.

When stopping a {{SparkContext}}, the {{stop}} method stops the DAG scheduler:

https://github.com/apache/spark/blob/a76cf51ed91d99c88f301ec85f3cda1288bcf346/core/src/main/scala/org/apache/spark/SparkContext.scala#L1722-L1727

and then stops the event logger:

https://github.com/apache/spark/blob/a76cf51ed91d99c88f301ec85f3cda1288bcf346/core/src/main/scala/org/apache/spark/SparkContext.scala#L1722-L1727

Though it is difficult to follow the chain of events, one of the sequelae of stopping the DAG scheduler is that the master's {{rebuildSparkUI}} method is called. This method looks for the application's event logs, and its behavior varies based on the existence of an {{.inprogress}} file suffix. In particular, a warning is logged if this suffix exists:

https://github.com/apache/spark/blob/a76cf51ed91d99c88f301ec85f3cda1288bcf346/core/src/main/scala/org/apache/spark/deploy/master/Master.scala#L935

After calling the {{stop}} method on the DAG scheduler, the {{SparkContext}} stops the event logger:

https://github.com/apache/spark/blob/a76cf51ed91d99c88f301ec85f3cda1288bcf346/core/src/main/scala/org/apache/spark/SparkContext.scala#L1734-L1736

This renames the event log, dropping the {{.inprogress}} file sequence.

As such, a race condition exists where the master may attempt to process the application log file before finalizing it.



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