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From Devaraj k <devara...@huawei.com>
Subject RE: Too many fetch failures. Help!
Date Mon, 26 Sep 2011 15:39:24 GMT
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.


From: bharath vissapragada [bharathvissapragada1990@gmail.com]
Sent: Monday, September 26, 2011 8:54 PM
To: common-user@hadoop.apache.org
Subject: Re: Too many fetch failures. Help!


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 <abdoukamel@gmail.com> 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

Bharath .V

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