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Redhat services in Python

Stuart D. Gathman stuart at bmsi.com
Wed Dec 11 21:49:43 EST 2002 
I have no problem writing AIX services in python.  However, Linux with
sysv-initscript (e.g. Redhat) is driving me crazy.  The standard service
wrappers communicate via signals.  Simple enough.  I can start a
python service no problem - but which pid (there is one for each thread)
to kill for terminate?  If I save the child PID after forking the python
interpreter, I get the same value as calling os.getpid() - but sending
signals to this PI has no effect.  Generally, the 3rd PID in a ps listing
is the one to send signals to.  But how can I get that PID reliably?  Is
it necessary to write a C wrapper for python services in RedHat?

Here is an example start script for a service:

#!/bin/sh
cd /var/log/milter
exec >>milter.log 2>&1
python2 bms.py &
echo $! >milter.pid

The python code does:

  print "bms milter startup, PID =",os.getpid()

and the output is:

bms milter startup, PID = 1195

Here are the running processes (PPID is shown via indent):

 RUSER      PID STIME TTY        TIME CMD
 root         1 Dec09 ?          0:07init [3] 
#mail      1195 21:32 pts/1      0:00 python2 bms.py
#mail      1198 21:32 pts/1      0:00  python2 bms.py
#mail      1199 21:32 pts/1      0:00   python2 bms.py

The contents of milter.pid is also 1195.  However, to terminate python
requires "kill 1199".

How do other people solve this problem?

-- 
	      Stuart D. Gathman <stuart at bmsi.com>
Business Management Systems Inc.  Phone: 703 591-0911 Fax: 703 591-6154
"Confutatis maledictis, flamis acribus addictis" - background song for
a Microsoft sponsored "Where do you want to go from here?" commercial.
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