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From Elazar Leibovich <elaz...@gmail.com>
Subject Re: Why Hadoop force using DNS?
Date Mon, 29 Jul 2013 15:11:54 GMT
This is a reason to force reverse resolution of IPs if they do not appear
in the dfs.allow. If the IP appear in dfs.allow, there's no reason to
reverse-resolve it.

On Mon, Jul 29, 2013 at 4:48 PM, Daryn Sharp <daryn@yahoo-inc.com> wrote:

>  One reason is the lists to accept or reject DN accepts hostnames.  If dns
> temporarily can't resolve an IP then an unauthorized DN might slip back
> into the cluster, or a decommissioning node might go back into service.
>  Daryn
>  On Jul 29, 2013, at 8:21 AM, 武泽胜 wrote:
>  I have the same confusion, anyone who can reply to this will be very
> appreciated.
>   From: Elazar Leibovich <elazarl@gmail.com>
> Reply-To: "user@hadoop.apache.org" <user@hadoop.apache.org>
> Date: Thursday, July 25, 2013 3:51 AM
> To: user <user@hadoop.apache.org>
> Subject: Why Hadoop force using DNS?
>   Looking at Hadoop source you can see that Hadoop relies on the fact
> each node has resolvable name.
>  For example, Hadoop 2 namenode reverse look the up of each node that
> connects to it. Also, there's no way way to tell a database to advertise an
> UP as it's address. Setting datanode.network.interface to, say, eth1, would
> cause Hadoop to reverse lookup UPs on eth1 and advertise the result.
>  Why is that? Using plain IPs is simple to set up, and I can't see a
> reason not to support them?

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