Python: subprocess loops forever

I'm trying to start/stop rsyslog through a python script:

RSYSLOG_INIT_SCRIPT='/etc/init.s/rsyslogd'
subprocess.call([RSYSLOG_INIT_SCRIPT,'stop'])

/etc/init.d/rsyslogd is a regular init sc开发者_开发知识库ript. The problem is that it continues executing this script again and again. (I've added an echo to the script to confirm this).

This is the stacktrace when i kill it:

  File "queuerunner.py", line 72, in <module>
    rsysloglauncher.startrsyslog()
  File "/root/logging-server/Logging-server-init/src/initializer/rsyslog/rsysloglauncher.py", line 23, in startrsyslog
    subprocess.call([RSYSLOG_INIT_SCRIPT,"stop"])
  File "/storage/local/python-2.6.4/lib/python2.6/subprocess.py", line 470, in call
    return Popen(*popenargs, **kwargs).wait()
  File "/storage/local/python-2.6.4/lib/python2.6/subprocess.py", line 1157, in wait
    pid, sts = os.waitpid(self.pid, 0)

---

Not sure what is going on, but try creating your shell script like this:

#!/bin/sh
while :
do
    echo "Sleeping..."
    sleep 1
done

Then confirm that your python program when running this script does the same thing.

Then confirm the python call with this script:

#!/bin/sh
echo "I will exit"

See if you can get more output from the original script, create a 'proxy' script - which you will call from your Python script.

#!/bin/sh
/etc/init.s/rsyslogd stop > /tmp/log 2>&1

And edit your original script to produce more output:

#!/bin/sh -xv

I'm assuming it's bourne-shell or bash.

Then call this script : and then check the /tmp/log with a :

tail -f /tmp/log

Also, can you get the :

subprocess.call(...

To return a PID of the process that is created ? If so, then track it using something like:

ps -eaf |grep <PID>

Where should be replaced by the actual PID of course.

Depending on OS, you might also be able to :

truss -o /tmp/truss.out <PID>

If this 'truss.out' continues to fill up with system calls, then you know your shell-script is looping - and then something differs (I'm not sure what yet) between the commandline invocation and the python invocation.

I agree with the other poster : it looks like the script is looping - rather than a problem strictly with the python script.

Another thing to try:

Right at the start of the script, echo out the arguments - you might find that it loops if it cannot get hold of the correct params or something.

---

Are you sure the script isn't looping itself? The python code looks like it's just waiting for the sub-process to exit.

Get the PID of the python script, then do:

watch pstree -ap <PID>

Look to see if the PID of the start/stop script is the same - maybe the python code is looping itself for some reason.

If the init.d script PID is constant, then do strace or truss on that PID to see what it's doing.