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From "Sameer Paranjpye (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-1263) retry logic when dfs exist or open fails temporarily, e.g because of timeout
Date Wed, 02 May 2007 17:20:15 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-1263?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12493148
] 

Sameer Paranjpye commented on HADOOP-1263:
------------------------------------------

Should the number of attempts and sleep time be configurable?

Maybe we should start with reasonable defaults in code and make these configurable if we discover
situations where they don't work. Let's not introduce config variables unless they are required.

> 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
>         Attachments: retry.patch
>
>
> 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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