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https://issues.apache.org/jira/browse/SPARK-26873?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Apache Spark reassigned SPARK-26873:
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Assignee: 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
> Assignee: Apache Spark
> 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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