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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