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https://issues.apache.org/jira/browse/KYLIN-4567?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17159290#comment-17159290
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ASF GitHub Bot commented on KYLIN-4567:
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zzcclp commented on pull request #1259:
URL: https://github.com/apache/kylin/pull/1259#issuecomment-659485193
LGTM
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> Improve TopN merge performance in MR engine
> -------------------------------------------
>
> Key: KYLIN-4567
> URL: https://issues.apache.org/jira/browse/KYLIN-4567
> Project: Kylin
> Issue Type: Improvement
> Components: Measure - TopN
> Reporter: Guangxu Cheng
> Assignee: Guangxu Cheng
> Priority: Major
>
> We have a cube that needs to calculate the TOPN of 13 columns. The number of
> data source is only 500k. But, the cubing job always fail when building base
> cuboid.
> we found that the map task always killed by the ApplicationMaster due to time
> out
> {noformat}
> ERROR-[-10001]-[MR]:[Mr Task
> Timeout]:[AttemptID:attempt_1591996262448_229922_m_000000_1 Timed out after
> 3600 secs!] ERROR-[-10015]-[MR]:[Container Exit Accidentally]:[Container
> killed by the ApplicationMaster. Container killed on request. Exit code is
> 143 Container exited with a non-zero exit code 143 ]
> {noformat}
> the stack information as below:
> {noformat}
> "SpillThread" #35 daemon prio=5 os_prio=0 tid=0x00007f9a89771800 nid=0x133a2
> runnable [0x00007f9a56e3f000]
> java.lang.Thread.State: RUNNABLE
> at java.util.LinkedList.toArray(LinkedList.java:1052)
> at java.util.List.sort(List.java:477)
> at java.util.Collections.sort(Collections.java:175)
> at
> org.apache.kylin.measure.topn.TopNCounter.sortAndRetain(TopNCounter.java:96)
> at
> org.apache.kylin.measure.topn.TopNCounter.merge(TopNCounter.java:183)
> at
> org.apache.kylin.measure.topn.TopNAggregator.aggregate(TopNAggregator.java:44)
> at
> org.apache.kylin.measure.topn.TopNAggregator.aggregate(TopNAggregator.java:27)
> at
> org.apache.kylin.measure.MeasureAggregators.aggregate(MeasureAggregators.java:83)
> at
> org.apache.kylin.engine.mr.steps.CuboidReducer.doReduce(CuboidReducer.java:108)
> at
> org.apache.kylin.engine.mr.steps.CuboidReducer.doReduce(CuboidReducer.java:44)
> at
> org.apache.kylin.engine.mr.KylinReducer.reduce(KylinReducer.java:77)
> at org.apache.hadoop.mapreduce.Reducer.run(Reducer.java:171)
> at
> org.apache.hadoop.mapred.Task$NewCombinerRunner.combine(Task.java:1688)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.sortAndSpill(MapTask.java:1645)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer.access$900(MapTask.java:884)
> at
> org.apache.hadoop.mapred.MapTask$MapOutputBuffer$SpillThread.run(MapTask.java:1540)
> {noformat}
> From the stack information, we found that sorting takes a lot of time. After
> merge another counter into this counter, need to re-sort this counter. Maybe
> we can reduce the frequency of sorting
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