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From "Sital Kedia (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (SPARK-15074) Spark shuffle service bottlenecked while fetching large amount of intermediate data
Date Mon, 02 May 2016 22:43:12 GMT

    [ https://issues.apache.org/jira/browse/SPARK-15074?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15267659#comment-15267659
] 

Sital Kedia commented on SPARK-15074:
-------------------------------------

[~rxin], [~srowen] - Please let me know what you think of the idea of having an LRU cache
to avoid open/close the index file or if you have any better idea?

> Spark shuffle service bottlenecked while fetching large amount of intermediate data
> -----------------------------------------------------------------------------------
>
>                 Key: SPARK-15074
>                 URL: https://issues.apache.org/jira/browse/SPARK-15074
>             Project: Spark
>          Issue Type: Improvement
>          Components: Shuffle
>    Affects Versions: 1.6.1
>            Reporter: Sital Kedia
>
> While running a job which produces more than 90TB of intermediate data, we find that
about 10-15% of the reducer execution time is being spent in shuffle fetch. 
> Jstack of the shuffle service reveals that most of the time the shuffle service is reading
the index files generated by the mapper. 
> {code}
> java.lang.Thread.State: RUNNABLE
> 	at java.io.FileInputStream.readBytes(Native Method)
> 	at java.io.FileInputStream.read(FileInputStream.java:255)
> 	at java.io.DataInputStream.readFully(DataInputStream.java:195)
> 	at java.io.DataInputStream.readLong(DataInputStream.java:416)
> 	at org.apache.spark.network.shuffle.ExternalShuffleBlockResolver.getSortBasedShuffleBlockData(ExternalShuffleBlockResolver.java:277)
> 	at org.apache.spark.network.shuffle.ExternalShuffleBlockResolver.getBlockData(ExternalShuffleBlockResolver.java:190)
> 	at org.apache.spark.network.shuffle.ExternalShuffleBlockHandler.handleMessage(ExternalShuffleBlockHandler.java:85)
> 	at org.apache.spark.network.shuffle.ExternalShuffleBlockHandler.receive(ExternalShuffleBlockHandler.java:72)
> 	at org.apache.spark.network.server.TransportRequestHandler.processRpcRequest(TransportRequestHandler.java:149)
> 	at org.apache.spark.network.server.TransportRequestHandler.handle(TransportRequestHandler.java:102)
> 	at org.apache.spark.network.server.TransportChannelHandler.channelRead0(TransportChannelHandler.java:104)
> 	at org.apache.spark.network.server.TransportChannelHandler.channelRead0(TransportChannelHandler.java:51)
> 	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
> 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
> 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
> 	at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:266)
> 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
> 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
> 	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:103)
> 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
> 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
> 	at org.apache.spark.network.util.TransportFrameDecoder.channelRead(TransportFrameDecoder.java:86)
> 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:308)
> 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:294)
> 	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:846)
> 	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:131)
> 	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:511)
> 	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:468)
> 	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:382)
> 	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:354)
> 	at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
> 	at java.lang.Thread.run(Thread.java:745)
> {code}
> The issue is that for each shuffle fetch, we reopen the same index file again and read
it. It would be much efficient, if we can avoid opening the same file multiple times and cache
the data. We can use an LRU cache to save the index file information. This way we can also
limit the number of entries in the cache so that we don't blow up the memory indefinitely.




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