Ryan Blue created SPARK-26873:
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Summary: 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: 2.4.0, 2.3.2, 2.2.3
Reporter: Ryan Blue
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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