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From "Doug Cutting (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HADOOP-197) Hook InetAddress.getLocalHost().getHostName() to support cluster simulatation.
Date Fri, 05 May 2006 18:45:28 GMT
    [ http://issues.apache.org/jira/browse/HADOOP-197?page=comments#action_12378098 ] 

Doug Cutting commented on HADOOP-197:

> Also, in general, I will wave my arms in the air and say that a single machine might
have any of several names and just using the one from InetAddress may not be the right thing
all the time [ ...]

Yes,  for sure.  The more common problem is with machines with multiple public ips, or hosts
that return the loopback address.  There isn't really a good way (yet) in java to get the
preferred public ip (if any) from a host.


I just wanted to understand whether this was the issue you were having, or something else.

I'm up for implementing this feature.  I don't particularly like the name InetAddressWrapper,
since it is not a complete wrapper.  So if we rename this NetworkUtils, then, unless someone
objects, I'm up for committing it.


> Hook InetAddress.getLocalHost().getHostName() to support cluster simulatation.
> ------------------------------------------------------------------------------
>          Key: HADOOP-197
>          URL: http://issues.apache.org/jira/browse/HADOOP-197
>      Project: Hadoop
>         Type: Improvement

>   Components: mapred, dfs
>  Environment: all
>     Reporter: alan wootton
>     Priority: Minor
>  Attachments: InetAddressWrapper.patch
> I have been running a simulation for weeks now (and also a 30 machine crawl). To make
it work I need to sometimes 
> let DataNodes, and TaskTrackers think they have a different machine-name than the one
in InetAddress.getLocalHost()
> The patch is:
> 1) replace InetAddress.getLocalHost().getHostName() with xxxx
> 	1.a)xxxx could be "conf.get("inetaddress.localhost.name",InetAddress.getLocalHost().getHostName())"
> 	1.b)or, xxxx could be a static call, I chose the latter: "InetAddressWrapper.getLocalHostName(conf)"
> 2) InetAddressWrapper.getLocalHostName(conf) checks the config for a hostname, and then
calls InetAddress.getLocalHost().getHostName()
> There's 3 places where it happens:
> DataNode
> DFSClient
> TaskTracker
> I did not patch the two tests that call InetAddress because they are not really using

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