Pidfile featuring stale detection and file-locking, can also be used as context-manager or decorator
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PidFile class featuring:
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']
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Logging to file is also possible when using PidFile with a daemon context manager
(e.g. python-daemon <https://pypi.python.org/pypi/python-daemon/>
_). This requires some care in
handling the open files when the daemon starts to avoid closing them, which causes problems with the
logging. In particular, the open handlers should be preserved::
import sys import logging import logging.config
import daemon from pid impor PidFile
logging.config.fileConfig(fname="logging.conf", disable_existing_loggers=False) log = logging.getLogger(name)
PIDNAME = "/tmp/mydaemon.pid"
def get_logging_handles(logger): handles = [] for handler in logger.handlers: handles.append(handler.stream.fileno()) if logger.parent: handles += get_logging_handles(logger.parent) return handles
def daemonize(): file_preserve = get_logging_handles(logging.root) pid_file = PidFile(pidname=PIDNAME)
with daemon.DaemonContext(stdout=sys.stdout,
stderr=sys.stderr,
stdin=sys.stdin,
pidfile=_pid_file,
files_preserve=files_preserve):
run_daemon_job()
print("DONE!")
if name == "main": daemonize()
This assumes a logging.conf
file has been created, see e.g. basic tutorial <https://docs.python.org/3/howto/logging.html#logging-basic-tutorial>
_ for logging.
PidFile can also be used a a decorator::
from pid.decorator import pidfile
@pidfile() def main(): pass
if name == "main": main()
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.
Changes in version 2.0.0 and going forward:
python-daemon <https://pypi.python.org/pypi/python-daemon/>
_ where
the PidFile context manager is passed as a parameter. The
new corrected behaviour will ensure the process environment is
determined 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.\
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.