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https://issues.apache.org/jira/browse/SPARK-26175?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16705842#comment-16705842
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Hyukjin Kwon commented on SPARK-26175:
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Thanks for pinging me - just checked. Let me take a look as well.
> PySpark cannot terminate worker process if user program reads from stdin
> ------------------------------------------------------------------------
>
> Key: SPARK-26175
> URL: https://issues.apache.org/jira/browse/SPARK-26175
> Project: Spark
> Issue Type: Bug
> Components: PySpark
> Affects Versions: 2.4.0
> Reporter: Ala Luszczak
> Priority: Major
> Labels: Hydrogen
>
> PySpark worker daemon reads from stdin the worker PIDs to kill.
> https://github.com/apache/spark/blob/1bb60ab8392adf8b896cc04fb1d060620cf09d8a/python/pyspark/daemon.py#L127
> However, the worker process is a forked process from the worker daemon
> process and we didn't close stdin on the child after fork. This means the
> child and user program can read stdin as well, which blocks daemon from
> receiving the PID to kill. This can cause issues because the task reaper
> might detect the task was not terminated and eventually kill the JVM.
> Possible fix could be:
> * Closing stdin of the worker process right after fork.
> * Creating a new socket to receive PIDs to kill instead of using stdin.
> h4. Steps to reproduce
> # Paste the following code in pyspark:
> {code}
> import subprocess
> def task(_):
> subprocess.check_output(["cat"])
> sc.parallelize(range(1), 1).mapPartitions(task).count()
> {code}
> # Press CTRL+C to cancel the job.
> # The following message is displayed:
> {code}
> 18/11/26 17:52:51 WARN PythonRunner: Incomplete task 0.0 in stage 0 (TID 0)
> interrupted: Attempting to kill Python Worker
> 18/11/26 17:52:52 WARN TaskSetManager: Lost task 0.0 in stage 0.0 (TID 0,
> localhost, executor driver): TaskKilled (Stage cancelled)
> {code}
> # Run {{ps -xf}} to see that {{cat}} process was in fact not killed:
> {code}
> 19773 pts/2 Sl+ 0:00 | | \_ python
> 19803 pts/2 Sl+ 0:11 | | \_
> /usr/lib/jvm/java-8-oracle/bin/java -cp
> /home/ala/Repos/apache-spark-GOOD-2/conf/:/home/ala/Repos/apache-spark-GOOD-2/assembly/target/scala-2.12/jars/*
> -Xmx1g org.apache.spark.deploy.SparkSubmit --name PySparkShell pyspark-shell
> 19879 pts/2 S 0:00 | | \_ python -m pyspark.daemon
> 19895 pts/2 S 0:00 | | \_ python -m pyspark.daemon
> 19898 pts/2 S 0:00 | | \_ cat
> {code}
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