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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-16) RPC call times out while indexing map task is computing splits
Date Thu, 16 Feb 2006 21:00:09 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-16?page=comments#action_12366680 ] 

Doug Cutting commented on HADOOP-16:
------------------------------------

But, you're right, Bryan, I think this is still not optimal.  It should certainly check to
see if more map tasks have local input data for the calling node before it gives up.  Ideally
it should not be iterating through all map tasks either, but rather create a mapping of node
-> mapTask* for tasks that have local data for a node.  We could keep a queue of tasks
whose entries in this table have not yet been computed.  When we fail to find a task with
local data for a node, then we can pop a few (10?) entries off the queue and enter them in
the map, and if there are still no matches, just give the node a task with remote input data.
 This way we'd avoid ever doing too much work in a single call, and ever iterating over all
tasks.

> RPC call times out while indexing map task is computing splits
> --------------------------------------------------------------
>
>          Key: HADOOP-16
>          URL: http://issues.apache.org/jira/browse/HADOOP-16
>      Project: Hadoop
>         Type: Bug
>   Components: mapred
>  Environment: MapReduce multi-computer crawl environment: 11 machines (1 master with
JobTracker/NameNode, 10 slaves with TaskTrackers/DataNodes)
>     Reporter: Chris Schneider
>  Attachments: patch.16
>
> We've been using Nutch 0.8 (MapReduce) to perform some internet crawling. Things seemed
to be going well until...
> 060129 222409 Lost tracker 'tracker_56288'
> 060129 222409 Task 'task_m_10gs5f' has been lost.
> 060129 222409 Task 'task_m_10qhzr' has been lost.
>    ........
>    ........
> 060129 222409 Task 'task_r_zggbwu' has been lost.
> 060129 222409 Task 'task_r_zh8dao' has been lost.
> 060129 222455 Server handler 8 on 8010 caught: java.net.SocketException: Socket closed
> java.net.SocketException: Socket closed
>         at java.net.SocketOutputStream.socketWrite(SocketOutputStream.java:99)
>         at java.net.SocketOutputStream.write(SocketOutputStream.java:136)
>         at java.io.BufferedOutputStream.flushBuffer(BufferedOutputStream.java:65)
>         at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:123)
>         at java.io.DataOutputStream.flush(DataOutputStream.java:106)
>         at org.apache.nutch.ipc.Server$Handler.run(Server.java:216)
> 060129 222455 Adding task 'task_m_cia5po' to set for tracker 'tracker_56288'
> 060129 223711 Adding task 'task_m_ffv59i' to set for tracker 'tracker_25647'
> I'm hoping that someone could explain why task_m_cia5po got added to tracker_56288 after
this tracker was lost.
> The Crawl .main process died with the following output:
> 060129 221129 Indexer: adding segment: /user/crawler/crawl-20060129091444/segments/20060129200246
> Exception in thread "main" java.io.IOException: timed out waiting for response
>     at org.apache.nutch.ipc.Client.call(Client.java:296)
>     at org.apache.nutch.ipc.RPC$Invoker.invoke(RPC.java:127)
>     at $Proxy1.submitJob(Unknown Source)
>     at org.apache.nutch.mapred.JobClient.submitJob(JobClient.java:259)
>     at org.apache.nutch.mapred.JobClient.runJob(JobClient.java:288)
>     at org.apache.nutch.indexer.Indexer.index(Indexer.java:263)
>     at org.apache.nutch.crawl.Crawl.main(Crawl.java:127)
> However, it definitely seems as if the JobTracker is still waiting for the job to finish
(no failed jobs).
> Doug Cutting's response:
> The bug here is that the RPC call times out while the map task is computing splits. 
The fix is that the job tracker should not compute splits until after it has returned from
the submitJob RPC.  Please submit a bug in Jira to help remind us to fix this.

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