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From "Apache Spark (JIRA)" <j...@apache.org>
Subject [jira] [Assigned] (SPARK-26873) FileFormatWriter creates inconsistent MR job IDs
Date Wed, 13 Feb 2019 23:02:00 GMT

     [ https://issues.apache.org/jira/browse/SPARK-26873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Apache Spark reassigned SPARK-26873:
------------------------------------

    Assignee:     (was: Apache Spark)

> FileFormatWriter creates inconsistent MR job IDs
> ------------------------------------------------
>
>                 Key: SPARK-26873
>                 URL: https://issues.apache.org/jira/browse/SPARK-26873
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.2.3, 2.3.2, 2.4.0
>            Reporter: Ryan Blue
>            Priority: Blocker
>              Labels: correctness
>
> FileFormatWriter uses the current time to create a Job ID that is used when calling Hadoop
committers. This ID is used to produce task and task attempt IDs used in commits.
> The problem is that Spark [generates this Job ID|https://github.com/apache/spark/blob/master/sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileFormatWriter.scala#L209]
in {{executeTask}} for every task:
> {code:lang=scala}
>   /** Writes data out in a single Spark task. */
>   private def executeTask(
>       description: WriteJobDescription,
>       sparkStageId: Int,
>       sparkPartitionId: Int,
>       sparkAttemptNumber: Int,
>       committer: FileCommitProtocol,
>       iterator: Iterator[InternalRow]): WriteTaskResult = {
>     val jobId = SparkHadoopWriterUtils.createJobID(new Date, sparkStageId)
>     val taskId = new TaskID(jobId, TaskType.MAP, sparkPartitionId)
>     val taskAttemptId = new TaskAttemptID(taskId, sparkAttemptNumber)
> ...
> {code}
> Because this is called in each task, the Job ID used is not consistent across tasks,
which violates the contract expected by Hadoop committers.
> If a committer expects identical task IDs across attempts for correctness, this breaks
correctness. For example, a Hadoop committer should be able to rename an output file to a
path based on the task ID to ensure that only one copy is committed.
> We hit this issue when preemption caused a task to die just after the commit operation.
The commit coordinator authorized a second task commit because the first did not complete
due to preemption.



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