[jira] [Resolved] (FLINK-3880) Improve performance of Accumulator map

["Maximilian Michels (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/FLINK-3880?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Maximilian Michels resolved FLINK-3880.
---------------------------------------
       Resolution: Fixed
    Fix Version/s: 1.1.0

Fixed with 9fccd6e5d626455174c830ba32eff06e60173020.

> Improve performance of Accumulator map
> --------------------------------------
>
>                 Key: FLINK-3880
>                 URL: https://issues.apache.org/jira/browse/FLINK-3880
>             Project: Flink
>          Issue Type: Improvement
>    Affects Versions: 1.1.0
>            Reporter: Ken Krugler
>            Assignee: Maximilian Michels
>            Priority: Minor
>             Fix For: 1.1.0
>
>
> I was looking at improving DataSet performance - this is for a job created using the Cascading-Flink planner for Cascading 3.1.
> While doing a quick "poor man's profiler" session with one of the TaskManager processes, I noticed that many (most?) of the threads that were actually running were in this state:
> {code:java}
> "DataSource (/working1/terms) (8/20)" daemon prio=10 tid=0x00007f55673e0800 nid=0x666a runnable [0x00007f556abcf000]
>    java.lang.Thread.State: RUNNABLE
>     at java.util.Collections$SynchronizedMap.get(Collections.java:2037)
>     - locked <0x00000006e73fe718> (a java.util.Collections$SynchronizedMap)
>     at org.apache.flink.api.common.functions.util.AbstractRuntimeUDFContext.getAccumulator(AbstractRuntimeUDFContext.java:162)
>     at org.apache.flink.api.common.functions.util.AbstractRuntimeUDFContext.getLongCounter(AbstractRuntimeUDFContext.java:113)
>     at com.dataartisans.flink.cascading.runtime.util.FlinkFlowProcess.getOrInitCounter(FlinkFlowProcess.java:245)
>     at com.dataartisans.flink.cascading.runtime.util.FlinkFlowProcess.increment(FlinkFlowProcess.java:128)
>     at com.dataartisans.flink.cascading.runtime.util.FlinkFlowProcess.increment(FlinkFlowProcess.java:122)
>     at cascading.tap.hadoop.util.MeasuredRecordReader.next(MeasuredRecordReader.java:65)
>     at cascading.scheme.hadoop.SequenceFile.source(SequenceFile.java:97)
>     at cascading.tuple.TupleEntrySchemeIterator.getNext(TupleEntrySchemeIterator.java:166)
>     at cascading.tuple.TupleEntrySchemeIterator.hasNext(TupleEntrySchemeIterator.java:139)
>     at com.dataartisans.flink.cascading.runtime.source.TapSourceStage.readNextRecord(TapSourceStage.java:70)
>     at com.dataartisans.flink.cascading.runtime.source.TapInputFormat.reachedEnd(TapInputFormat.java:175)
>     at org.apache.flink.runtime.operators.DataSourceTask.invoke(DataSourceTask.java:173)
>     at org.apache.flink.runtime.taskmanager.Task.run(Task.java:559)
>     at java.lang.Thread.run(Thread.java:745)}}}
> {code}
> It looks like Cascading is asking Flink to increment a counter with each Tuple read, and that in turn is often blocked on getting access to the Accumulator object in a map. It looks like this is a SynchronizedMap, but using a ConcurrentHashMap (for example) would reduce this contention.



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