Python execute remote command and don't wait for return

Question

I'm working on testing a corosync cluster. I'm trying to fail the interface that has the floating-IP to ensure the resource migrates over to another node with python.

Now the dilemma is my command does execute on the remote machine, but my test code hangs forever waiting for a reply it will never get--thenode will get rebooted because of the injected failure.

ssh = SSHClient(self.get_ms_ip(ms),
                        self.get_ms_user(ms),
                        self.get_ms_password(ms))
ssh.connect()
self.logger.info("Failing FIP eth now on %s" % ms)
ssh.exec_command(cmd, timeout=1)
#Code never reached this comment.

In python, how can I send the command and just continue on without waiting for any return? I've tried wrapping my ssh.exec_command with subprocess.Popen as suggested here Run Process and Don't Wait but that didn't yield anything different.

Similarly worded question – although about different problem – not waiting for long/infinite commands – I believe most users who come here will actually look for that: Do not wait for commands to finish when executing them with Python Paramiko. — Martin Prikryl
– Martin Prikryl, Commented Feb 10, 2021 at 7:10

Colin vH · Accepted Answer · 2014-11-29 06:18:27Z

2

You don't want a subprocess, you want a thread. Spawn a thread that runs the exec_command call and you'll be able to continue with your code.

answered Nov 29, 2014 at 6:18

Colin vH

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HayatoY · Accepted Answer · 2014-11-29 06:21:41Z

0

Did you try nohup?

ssh.exec_command('nohup %s &'%cmd, timeout=1)

answered Nov 29, 2014 at 6:21

HayatoY

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2 Comments

user597608 Over a year ago

Tried nohup and the code does continue but now my cmd is failing. Following is my cmd: cmd = "echo %s | sudo -S ifdown eth3" % self.get_ms_root_password(ms)

HayatoY Over a year ago

try this wrapper. easier to exec sudo commands. stackoverflow.com/a/22592827/2854735

user597608 · Accepted Answer · 2014-12-03 00:44:39Z

0

Python doesn't handle threads nicely; can't manually exit a thread. I ended up having to make a worker method that would create the shh connection and run exec_command that would be run as a seperate multiprocessing.Process.

This way I was able to cleanup after a test properly before the next test ran (as part of python's unit test framework).

answered Dec 3, 2014 at 0:44

user597608

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