I'm using python-daemon, and having the problem that when I kill -9 a process, it leaves a pidfile behind (ok) and the next time I run my program it doesn't work unless I have already removed the pidfile by hand (not ok).
I catch all exceptions in order that context.close() is called before terminating -- when this happens (e.g. on a kill) the /var/run/mydaemon.pid* files are removed and a subsequent daemon run succeeds. However, when using SIGKILL (kill -9), I don't have the chance to call context.close(), and the /var/run files remain. In this instance, the next time I run my program it does not start successfully -- the original process returns, but the daemonized process blocks at context.open().
It seems like python-daemon ought to be noticing that there is a pidfile for a process that no longer exists, and clearing it out, but that isn't happening. Am I supposed to be doing this by hand?
Note: I'm not using with because this code runs on Python 2.4
from daemon import DaemonContext
from daemon.pidlockfile import PIDLockFile
context = DaemonContext(pidfile = PIDLockFile("/var/run/mydaemon.pid"))
context.open()
try:
retry_main_loop()
except Exception, e:
pass
context.close()
If you are running linux, and process level locks are acceptable, read on.
We try to acquire the lock. If it fails, check if the lock is acquired by a running process. If no, break the lock and continue.
from lockfile.pidlockfile import PIDLockFile
from lockfile import AlreadyLocked
pidfile = PIDLockFile("/var/run/mydaemon.pid", timeout=-1)
try:
pidfile.acquire()
except AlreadyLocked:
try:
os.kill(pidfile.read_pid(), 0)
print 'Process already running!'
exit(1)
except OSError: #No process with locked PID
pidfile.break_lock()
#pidfile can now be used to create DaemonContext
Edit: Looks like PIDLockFile is available only on lockfile >= 0.9