Hi all,
Updated - I found the logging for the error, and it’s happening during a GroupReduce. This is also happening at the same time as the leftOuterJoin and the CoGroup.
Caused by: java.io.FileNotFoundException: /mnt/yarn/usercache/hadoop/appcache/application_1600303450883_0004/flink-io-719a95fa-eca4-4ac4-b2c5-7799315b626d/87cb5c578a889080d681cc00fc11023b.000001.channel (Too many open files)
at java.io.RandomAccessFile.open0(Native Method) ~[?:1.8.0_252]
at java.io.RandomAccessFile.open(RandomAccessFile.java:316) ~[?:1.8.0_252]
at java.io.RandomAccessFile.<init>(RandomAccessFile.java:243) ~[?:1.8.0_252]
at java.io.RandomAccessFile.<init>(RandomAccessFile.java:124) ~[?:1.8.0_252]
at org.apache.flink.runtime.io.disk.iomanager.AbstractFileIOChannel.<init>(AbstractFileIOChannel.java:57) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.io.disk.iomanager.AsynchronousFileIOChannel.<init>(AsynchronousFileIOChannel.java:87) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.io.disk.iomanager.AsynchronousBlockReader.<init>(AsynchronousBlockReader.java:60) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.io.disk.iomanager.IOManagerAsync.createBlockChannelReader(IOManagerAsync.java:224) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.io.disk.iomanager.IOManager.createBlockChannelReader(IOManager.java:182) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$SpillingThread.getMergingIterator(UnilateralSortMerger.java:1543) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$SpillingThread.go(UnilateralSortMerger.java:1475) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
at org.apache.flink.runtime.operators.sort.UnilateralSortMerger$ThreadBase.run(UnilateralSortMerger.java:827) ~[flink-dist_2.12-1.11.1.jar:1.11.1]
I’m curious if increasing taskmanager.memory.segment-size would have an impact here (I assume it would still reduce the total number of open files being used by the leftOuterJoin and probably the CoGroup)
Thanks,
— Ken
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When I do a leftOuterJoin(stream, JoinHint.REPARTITION_SORT_MERGE), I’m running into an IOException caused by too many open files.
The slaves in my YARN cluster (each with 48 slots and 320gb memory) are currently set up with a limit of 32767, so I really don’t want to crank this up much higher.
In perusing the code, I assume the issue is that SpillingBuffer.nextSegment() can open a writer per segment.
So if I have a lot of data (e.g. several TBs) that I’m joining, I can wind up with > 32K segments that are open for writing.
Does that make sense? And is the best solution currently (without say using more, smaller servers to reduce the per-server load) to increase the taskmanager.memory.segment-size configuration setting from 32K to something larger, so I’d have fewer active segments?
If I do that, any known side-effects I should worry about?
Thanks,
— Ken
PS - a CoGroup is happening at the same time, so it’s possible that’s also hurting (or maybe the real source of the problem), but the leftOuterJoin failed first.
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Ken Krugler
http://www.scaleunlimited.comcustom big data solutions & training
Hadoop, Cascading, Cassandra & Solr
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