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https://issues.apache.org/jira/browse/HDFS-3618?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13418935#comment-13418935
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Uma Maheswara Rao G commented on HDFS-3618:
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Hi Eli, Thanks a lot for taking a look.
I think we have to handle 127 and 126 code separateltly and return false as
they indicate command not exist or doesn't have
permissions.http://theory.uwinnipeg.ca/localfiles/infofiles/bash/bashref_43.html#SEC50
{quote}
Looks like we return ChannelExec#getExitStatus, which may return non-zero
values, eg -1.
{quote}
When I checked the changeLog of JSCh, I observed below change.
{quote}
•feature: added 'Channel.isClosed()'. Channel.getExitStatus() should be invoked
after Channel.isClosed()==true.
{quote}
Looking at our code, we are not calling in that way right?
After calling status only we are disconnecting in finally.
{code}
return exec.getExitStatus();
} finally {
cleanup(exec);
}
{code}
I found a case where we have to call ChannelExec#getExitStatus after
Channel.isClosed()==true
do you think we have to hanlde this case?
> 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
> Affects Versions: 2.1.0-alpha
> 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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