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https://issues.apache.org/jira/browse/SPARK-21971?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]
Takeshi Yamamuro closed SPARK-21971.
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Resolution: Not A Problem
> Too many open files in Spark due to concurrent files being opened
> -----------------------------------------------------------------
>
> Key: SPARK-21971
> URL: https://issues.apache.org/jira/browse/SPARK-21971
> Project: Spark
> Issue Type: Bug
> Components: Spark Core, SQL
> Affects Versions: 2.1.0, 2.2.0
> Reporter: Rajesh Balamohan
> Priority: Minor
>
> When running Q67 of TPC-DS at 1 TB dataset on multi node cluster, it
> consistently fails with "too many open files" exception.
> {noformat}
> O scheduler.TaskSetManager: Finished task 25.0 in stage 844.0 (TID 243786) in
> 394 ms on machine111.xyz (executor 2) (189/200)
> 17/08/20 10:33:45 INFO scheduler.TaskSetManager: Finished task 172.0 in stage
> 844.0 (TID 243932) in 11996 ms on cn116-10.l42scl.hortonworks.com (executor
> 6) (190/200)
> 17/08/20 10:37:40 WARN scheduler.TaskSetManager: Lost task 144.0 in stage
> 844.0 (TID 243904, machine1.xyz, executor 1):
> java.nio.file.FileSystemException:
> /grid/3/hadoop/yarn/local/usercache/rbalamohan/appcache/application_1490656001509_7207/blockmgr-5180e3f0-f7ed-44bb-affc-8f99f09ba7bc/28/temp_local_690afbf7-172d-4fdb-8492-3e2ebd8d5183:
> Too many open files
> at
> sun.nio.fs.UnixException.translateToIOException(UnixException.java:91)
> at
> sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
> at
> sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
> at
> sun.nio.fs.UnixFileSystemProvider.newFileChannel(UnixFileSystemProvider.java:177)
> at java.nio.channels.FileChannel.open(FileChannel.java:287)
> at java.nio.channels.FileChannel.open(FileChannel.java:335)
> at
> org.apache.spark.io.NioBufferedFileInputStream.<init>(NioBufferedFileInputStream.java:43)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeSorterSpillReader.<init>(UnsafeSorterSpillReader.java:75)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeSorterSpillWriter.getReader(UnsafeSorterSpillWriter.java:150)
> at
> org.apache.spark.util.collection.unsafe.sort.UnsafeExternalSorter.getIterator(UnsafeExternalSorter.java:607)
> at
> org.apache.spark.sql.execution.ExternalAppendOnlyUnsafeRowArray.generateIterator(ExternalAppendOnlyUnsafeRowArray.scala:169)
> at
> org.apache.spark.sql.execution.ExternalAppendOnlyUnsafeRowArray.generateIterator(ExternalAppendOnlyUnsafeRowArray.scala:173)
> {noformat}
> Cluster was configured with multiple cores per executor.
> Window function uses "spark.sql.windowExec.buffer.spill.threshold=4096" which
> causes large number of spills in larger dataset. With multiple cores per
> executor, this reproduces easily.
> {{UnsafeExternalSorter::getIterator()}} invokes {{spillWriter.getReader}} for
> all the available spillWriters. {{UnsafeSorterSpillReader}} opens up the file
> in its constructor and closes the file later as a part of its close() call.
> This causes too many open files issue.
> Note that this is not a file leak, but more of concurrent files being open at
> any given time depending on the dataset being processed.
> One option could be to increase "spark.sql.windowExec.buffer.spill.threshold"
> so that fewer spill files are generated, but it is hard to determine the
> sweetspot for all workload. Another option is to set ulimit to "unlimited"
> for files, but that would not be a good production setting. It would be good
> to consider reducing the number of concurrent
> "UnsafeExternalSorter::getIterator".
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