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Hadoop, mail # user - Too many fetch failures. Help!


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RE: Too many fetch failures. Help!
Devaraj k 2011-09-26, 15:39
Hi Bharath,

There are few reasons to cause this problem. I have listed below some reasons with solutions. This might help you to solve this. If you post the logs, the problem can be figured out.
Reason 1:
It could be that the mapping in the /etc/hosts file is not present.
The DNS server is down as a result of which the hostnames cannot be resolved.
The DNS server is in-correctly configured.

Solution: Setting the slave.host.name property can be one solution.  Appropriate changes need to be done based on the problem.
Reason 2: If the map outputs are larger, we may get java.lang.OutOfMemoryError: Java heap space. Because of this there are too many fetch failures.

Solution: The error, java.lang.OutOfMemoryError: Java heap space in task tracker logs can be solved by any of the following methods:

By decreasing the value configured for mapred.job.shuffle.input.buffer.percent.
By increasing the heap memory of child JVM options for the property mapred.child.java.opts.
Thanks
Devaraj

________________________________________
From: bharath vissapragada [[EMAIL PROTECTED]]
Sent: Monday, September 26, 2011 8:54 PM
To: [EMAIL PROTECTED]
Subject: Re: Too many fetch failures. Help!

Hey,

Try configuring your cluster with hostnames instead of ips and add
those entries to /etc/hosts and sync it across all the nodes in the
cluster. You need to restart the cluster after making these changes.

Hope this helps,

On Mon, Sep 26, 2011 at 8:46 PM, Abdelrahman Kamel <[EMAIL PROTECTED]> wrote:
> Hi,
> This is my first post here.
> I'm new to Hadoop.
> I've already installed Hadoop on 2 Ubuntu boxes (one is both master and
> slave and the other is only slave).
> When I run a Wordcount example on 5 small txt files, the process never
> completes and I get a "Too many fetch failures" error on my terminal.
> If you can help me, I cant post my terminal's output and any log files
> needed.
> Great thanks.
>
> --
> Abdelrahman Kamel
>

--
Regards,
Bharath .V
w:http://researchweb.iiit.ac.in/~bharath.v