pid
PidFile class featuring:
- stale detection
- pidfile locking (fcntl)
- chmod (default is 0o644)
- chown
- custom exceptions
Context Manager
PidFile can be used as a context manager:
from pid import PidFile
import os
with PidFile('foo') as p:
print(p.pidname) # -> 'foo'
print(p.piddir) # -> '/var/run' But you can modify it when initialize PidFile.
print(os.listdir('/var/run')) # -> ['foo.pid']
# pid file will delete after 'with' literal.
Decorator
PidFile can also be used a a decorator:
from pid.decorator import pidfile @pidfile() def main(): pass if __name__ == "__main__": main()
Exception Order
In default mode PidFile will try to acquire a file lock before anything else. This means that normally you get a PidFileAlreadyLockedError instead of the PidFileAlreadyRunningError when running a program twice.
If you just want to know if a program is already running its easiest to catch just PidFileError since it will capture all possible PidFile exceptions.
Behaviour
Changes in version 2.0.0 and going forward:
- pid is now friendly with daemon context managers such as python-daemon where the PidFile context manager is passed as a parameter. The new corrected behaviour will ensure the process environment is determinde at the time of acquiring/checking the lock. Prior behaviour would determine the process environment when instancing the class which may result in incorrect determination of the PID in the case of a process forking after instancing PidFile.
- Cleanup of pidfile on termination is done using atexit module. The default SIGTERM handler doesn't cleanly exit and therefore the atexit registered functions will not execute. A custom handler which triggers the atexit registered functions for cleanup will override the default SIGTERM handler. If a prior signal handler has been configured, then it will not be overridden.