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From "Harsh J (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-7198) Hadoop defaults for web UI ports often fall smack in the middle of Linux ephemeral port range
Date Wed, 15 Jun 2011 17:17:47 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-7198?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13049900#comment-13049900
] 

Harsh J commented on HADOOP-7198:
---------------------------------

I guess we could make a documentation note at most for this.

Do you have any other ideas in mind?

> Hadoop defaults for web UI ports often fall smack in the middle of Linux ephemeral port
range
> ---------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-7198
>                 URL: https://issues.apache.org/jira/browse/HADOOP-7198
>             Project: Hadoop Common
>          Issue Type: Wish
>            Reporter: Philip Zeyliger
>            Priority: Trivial
>
> It turns out (see http://en.wikipedia.org/wiki/Ephemeral_port and  /proc/sys/net/ipv4/ip_local_port_range)
that when you bind to port 0, Linux chooses an ephemeral port.  On my default-ridden Ubuntu
Maverick box and on CentOS 5.5, that range is 32768-61000.  So, when HBase binds to 60030
or when mapReduce binds to 50070, there's a small chance that you'll conflict with, say, an
FTP session, or with some other Hadoop daemon that's had a listening address configured as
:0.
> I don't know that there's a practical resolution here, since changing the defaults seems
like an ill-fated effort, but if you have any ephemeral port use, you can run into this. 
We've now run into it once.

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