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From "Mridul Muralidharan (JIRA)" <>
Subject [jira] [Commented] (SPARK-3277) LZ4 compression cause the the ExternalSort exception
Date Thu, 28 Aug 2014 22:25:10 GMT


Mridul Muralidharan commented on SPARK-3277:

Sounds great, thx !
I suspect it is because for lzo we configure it to write block on flush (partial if insufficient
data to fill block); but for lz4, either such config does not exist or we dont use that.
Resulting in flush becoming noop in case the data in current block is insufficientto cause
a compressed block to be created - while close will force patial block to be written out.

Which is why the asserion lists all sizes as 0

> LZ4 compression cause the the ExternalSort exception
> ----------------------------------------------------
>                 Key: SPARK-3277
>                 URL:
>             Project: Spark
>          Issue Type: Bug
>          Components: Spark Core
>    Affects Versions: 1.0.2, 1.1.0, 1.2.0
>            Reporter: hzw
>            Assignee: Andrew Or
>            Priority: Blocker
>         Attachments: test_lz4_bug.patch
> I tested the LZ4 compression,and it come up with such problem.(with wordcount)
> Also I tested the snappy and LZF,and they were OK.
> At last I set the  "spark.shuffle.spill" as false to avoid such exeception, but once
open this "switch", this error would come.
> It seems that if num of the[ words is few, wordcount will go through,but if it is a complex
text ,this problem will show
> Exeception Info as follow:
> {code}
> java.lang.AssertionError: assertion failed
>         at scala.Predef$.assert(Predef.scala:165)
>         at org.apache.spark.util.collection.ExternalAppendOnlyMap$DiskMapIterator.<init>(ExternalAppendOnlyMap.scala:416)
>         at org.apache.spark.util.collection.ExternalAppendOnlyMap.spill(ExternalAppendOnlyMap.scala:235)
>         at org.apache.spark.util.collection.ExternalAppendOnlyMap.insertAll(ExternalAppendOnlyMap.scala:150)
>         at org.apache.spark.Aggregator.combineValuesByKey(Aggregator.scala:58)
>         at org.apache.spark.shuffle.hash.HashShuffleWriter.write(HashShuffleWriter.scala:55)
>         at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:68)
>         at org.apache.spark.scheduler.ShuffleMapTask.runTask(ShuffleMapTask.scala:41)
>         at
>         at org.apache.spark.executor.Executor$
>         at java.util.concurrent.ThreadPoolExecutor.runWorker(
>         at java.util.concurrent.ThreadPoolExecutor$
>         at
> {code}

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