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https://issues.apache.org/jira/browse/HDFS-3618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13410144#comment-13410144
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Uma Maheswara Rao G commented on HDFS-3618:
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We should treat that as fence failed, in 'command not found' case.
In other part, I am wordering why it is hanging? Because, StreamPumper is just
uses BufferedReader. ReadLine will wait for the input on comsole. It should
print command not found message right?
Untill it reads line, it will wait there.
We may have to read the line only when it is really ready, can we make use of
BufferedReader#ready api?
Within the fenceTimeout, if the stream is not ready then, we can return false
instead of waiting for the input forever?
> SSH fencing option may incorrectly succeed if nc (netcat) command not present
> -----------------------------------------------------------------------------
>
> Key: HDFS-3618
> URL: https://issues.apache.org/jira/browse/HDFS-3618
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: auto-failover
> Reporter: Brahma Reddy Battula
> Attachments: zkfc.txt, zkfc_threaddump.out
>
>
> Started NN's and zkfc's in Suse11.
> Suse11 will have netcat installation and netcat -z will work(but nc -z wn't
> work)..
> While executing following command, got command not found hence rc will be
> other than zero and assuming that server was down..Here we are ending up
> without checking whether service is down or not..
> {code}
> LOG.info(
> "Indeterminate response from trying to kill service. " +
> "Verifying whether it is running using nc...");
> rc = execCommand(session, "nc -z " + serviceAddr.getHostName() +
> " " + serviceAddr.getPort());
> if (rc == 0) {
> // the service is still listening - we are unable to fence
> LOG.warn("Unable to fence - it is running but we cannot kill it");
> return false;
> } else {
> LOG.info("Verified that the service is down.");
> return true;
> }
> {code}
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