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Date: Wed, 25 Apr 2007 11:51:16 -0700 (PDT)
From: "Hairong Kuang (JIRA)" <jira@apache.org>
To: hadoop-dev@lucene.apache.org
Subject: [jira] Commented: (HADOOP-1263) retry logic when dfs exist or open
 fails temporarily, e.g because of timeout
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    [ https://issues.apache.org/jira/browse/HADOOP-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12491730 ] 

Hairong Kuang commented on HADOOP-1263:
---------------------------------------

Tome, thank you so much. Owen also mentioned the retry package to me yesterday. I start to take a look at it and try to figure out how to use it. The info that you provided is definitely helpful.

> retry logic when dfs exist or open fails temporarily, e.g because of timeout
> ----------------------------------------------------------------------------
>
>                 Key: HADOOP-1263
>                 URL: https://issues.apache.org/jira/browse/HADOOP-1263
>             Project: Hadoop
>          Issue Type: Improvement
>          Components: dfs
>    Affects Versions: 0.12.3
>            Reporter: Christian Kunz
>         Assigned To: Hairong Kuang
>
> Sometimes, when many (e.g. 1000+) map jobs start at about the same time and require supporting files from filecache, it happens that some map tasks fail because of rpc timeouts. With only the default number of 10 handlers on the namenode, the probability is high that the whole job fails (see Hadoop-1182). It is much better with a higher number of handlers, but some map tasks still fail.
> This could be avoided if rpc clients did retry when encountering a timeout before throwing an exception.
> Examples of exceptions:
> java.net.SocketTimeoutException: timed out waiting for rpc response
> at org.apache.hadoop.ipc.Client.call(Client.java:473)
> at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:163)
> at org.apache.hadoop.dfs.$Proxy1.exists(Unknown Source)
> at org.apache.hadoop.dfs.DFSClient.exists(DFSClient.java:320)
> at org.apache.hadoop.dfs.DistributedFileSystem$RawDistributedFileSystem.exists(DistributedFileSystem.java:170)
> at org.apache.hadoop.dfs.DistributedFileSystem$RawDistributedFileSystem.open(DistributedFileSystem.java:125)
> at org.apache.hadoop.fs.ChecksumFileSystem$FSInputChecker.(ChecksumFileSystem.java:110)
> at org.apache.hadoop.fs.ChecksumFileSystem.open(ChecksumFileSystem.java:330)
> at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:245)
> at org.apache.hadoop.filecache.DistributedCache.createMD5(DistributedCache.java:327)
> at org.apache.hadoop.filecache.DistributedCache.ifExistsAndFresh(DistributedCache.java:253)
> at org.apache.hadoop.filecache.DistributedCache.localizeCache(DistributedCache.java:169)
> at org.apache.hadoop.filecache.DistributedCache.getLocalCache(DistributedCache.java:86)
> at org.apache.hadoop.mapred.TaskRunner.run(TaskRunner.java:117)
> java.net.SocketTimeoutException: timed out waiting for rpc response
>         at org.apache.hadoop.ipc.Client.call(Client.java:473)
>         at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:163)
>         at org.apache.hadoop.dfs.$Proxy1.open(Unknown Source)
>         at org.apache.hadoop.dfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:511)
>         at org.apache.hadoop.dfs.DFSClient$DFSInputStream.<init>(DFSClient.java:498)
>         at org.apache.hadoop.dfs.DFSClient.open(DFSClient.java:207)
>         at org.apache.hadoop.dfs.DistributedFileSystem$RawDistributedFileSystem.open(DistributedFileSystem.java:129)
>         at org.apache.hadoop.fs.ChecksumFileSystem$FSInputChecker.<init>(ChecksumFileSystem.java:110)
>         at org.apache.hadoop.fs.ChecksumFileSystem.open(ChecksumFileSystem.java:330)
>         at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:245)
>         at org.apache.hadoop.fs.FileUtil.copy(FileUtil.java:82)
>         at org.apache.hadoop.fs.ChecksumFileSystem.copyToLocalFile(ChecksumFileSystem.java:577)
>         at org.apache.hadoop.fs.FileSystem.copyToLocalFile(FileSystem.java:766)
>         at org.apache.hadoop.mapred.TaskTracker.localizeJob(TaskTracker.java:370)
>         at org.apache.hadoop.mapred.TaskTracker.startNewTask(TaskTracker.java:877)
>         at org.apache.hadoop.mapred.TaskTracker.offerService(TaskTracker.java:545)
>         at org.apache.hadoop.mapred.TaskTracker.run(TaskTracker.java:913)
>         at org.apache.hadoop.mapred.TaskTracker.main(TaskTracker.java:1603)

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