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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-210) Namenode not able to accept connections
Date Wed, 24 May 2006 23:11:30 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-210?page=comments#action_12413195 ] 

Doug Cutting commented on HADOOP-210:
-------------------------------------

Alan, yes, changing Server.java to use nio's Selector is what's under discussion, using a
single thread on the server to buffer requests until they are complete, then dispatching each
request to a worker thread.  Client.java must also be modified to buffer request objects so
that they can be written preceded by their size, permitting Server.java to determine when
each request has fully arrived.

> Namenode not able to accept connections
> ---------------------------------------
>
>          Key: HADOOP-210
>          URL: http://issues.apache.org/jira/browse/HADOOP-210
>      Project: Hadoop
>         Type: Bug

>   Components: dfs
>  Environment: linux
>     Reporter: Mahadev konar
>     Assignee: Mahadev konar

>
> I am running owen's random writer on a 627 node cluster (writing 10GB/node).  After running
for a while (map 12% reduce 1%) I get the following error on the Namenode:
> Exception in thread "Server listener on port 60000" java.lang.OutOfMemoryError: unable
to create new native thread
>         at java.lang.Thread.start0(Native Method)
>         at java.lang.Thread.start(Thread.java:574)
>         at org.apache.hadoop.ipc.Server$Listener.run(Server.java:105)
> After this, the namenode does not seem to be accepting connections from any of the clients.
All the DFSClient calls get timeout. Here is a trace for one of them:
> java.net.SocketTimeoutException: timed out waiting for rpc response
> 	at org.apache.hadoop.ipc.Client.call(Client.java:305)
> 	at org.apache.hadoop.ipc.RPC$Invoker.invoke(RPC.java:149)
> 	at org.apache.hadoop.dfs.$Proxy1.open(Unknown Source)
> 	at org.apache.hadoop.dfs.DFSClient$DFSInputStream.openInfo(DFSClient.java:419)
> 	at org.apache.hadoop.dfs.DFSClient$DFSInputStream.(DFSClient.java:406)
> 	at org.apache.hadoop.dfs.DFSClient.open(DFSClient.java:171)
> 	at org.apache.hadoop.dfs.DistributedFileSystem.openRaw(DistributedFileSystem.java:78)
> 	at org.apache.hadoop.fs.FSDataInputStream$Checker.(FSDataInputStream.java:46)
> 	at org.apache.hadoop.fs.FSDataInputStream.(FSDataInputStream.java:228)
> 	at org.apache.hadoop.fs.FileSystem.open(FileSystem.java:157)
> 	at org.apache.hadoop.mapred.TextInputFormat.getRecordReader(TextInputFormat.java:43)
> 	at org.apache.hadoop.mapred.MapTask.run(MapTask.java:105)
> 	at org.apache.hadoop.mapred.TaskTracker$Child.main(TaskTracker.java:785).
> The namenode then has around 1% CPU utilization at this time (after the outofmemory exception
has been thrown). I have profiled the NameNode and it seems to be using around a maixmum heap
size of 57MB (which is not much). So, heap size does not seem to be a problem. It might be
happening due to lack of Stack space? Any pointers?

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