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Posted to common-dev@hadoop.apache.org by "Philip Zeyliger (JIRA)" <ji...@apache.org> on 2011/03/18 00:44:29 UTC

[jira] Created: (HADOOP-7198) Hadoop defaults for web UI ports often fall smack in the middle of Linux ephemeral port range

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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