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https://issues.apache.org/jira/browse/HDFS-3081?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Eli Collins updated HDFS-3081:
------------------------------
Target Version/s: 0.23.3 (was: 0.24.0)
> SshFenceByTcpPort uses netcat incorrectly
> -----------------------------------------
>
> Key: HDFS-3081
> URL: https://issues.apache.org/jira/browse/HDFS-3081
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: ha
> Affects Versions: 0.24.0
> Reporter: Philip Zeyliger
> Assignee: Todd Lipcon
>
> SshFencyByTcpPort currently assumes that the NN is listening on localhost.
> Typical setups have the namenode listening just on the hostname of the
> namenode, which would lead "nc -z" to not catch it.
> Here's an example in which the NN is running, listening on 8020, but doesn't
> respond to "localhost 8020".
> {noformat}
> [root@xxx ~]# lsof -P -p 5286 | grep -i listen
> java 5286 root 110u IPv4 1772357 TCP xxx:8020
> (LISTEN)
> java 5286 root 121u IPv4 1772397 TCP xxx:50070
> (LISTEN)
> [root@xxx ~]# nc -z localhost 8020
> [root@xxx ~]# nc -z xxx 8020
> Connection to xxx 8020 port [tcp/intu-ec-svcdisc] succeeded!
> {noformat}
> Here's the likely offending code:
> {code}
> LOG.info(
> "Indeterminate response from trying to kill service. " +
> "Verifying whether it is running using nc...");
> rc = execCommand(session, "nc -z localhost 8020");
> {code}
> Naively, we could rely on netcat to the correct hostname (since the NN ought
> to be listening on the hostname it's configured as), or just to use fuser.
> Fuser catches ports independently of what IPs they're bound to:
> {noformat}
> [root@xxx ~]# fuser 1234/tcp
> 1234/tcp: 6766 6768
> [root@xxx ~]# jobs
> [1]- Running nc -l localhost 1234 &
> [2]+ Running nc -l rhel56-18.ent.cloudera.com 1234 &
> [root@xxx ~]# sudo lsof -P | grep -i LISTEN | grep -i 1234
> nc 6766 root 3u IPv4 2563626
> TCP localhost:1234 (LISTEN)
> nc 6768 root 3u IPv4 2563671
> TCP xxx:1234 (LISTEN)
> {noformat}
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