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From "Philip Zeyliger (JIRA)" <j...@apache.org>
Subject [jira] Created: (HADOOP-7198) Hadoop defaults for web UI ports often fall smack in the middle of Linux ephemeral port range
Date Thu, 17 Mar 2011 23:44:29 GMT
Hadoop defaults for web UI ports often fall smack in the middle of Linux ephemeral port range
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                 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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