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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