make sure only one processing running on the system

single_process_lock.py

import fcntl
import sys
from contextlib import contextmanager
from os.path import isfile

from absl import logging as log


@contextmanager
def single_process_lock(lockfile: str):
    fp = open(lockfile, "w")
    fp.flush()
    try:
        fcntl.lockf(fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
    except IOError:
        log.error("another instance is already running.")
        sys.exit(1)

    yield fp

    fcntl.lockf(fp, fcntl.LOCK_UN)
    if isfile(lockfile):
        os.unlink(lockfile)
        
        
if __name__ == "__main__":
  import tempfile
  from os.path import join
  with single_proess_lock(tempfile.gettempdir(), "myprocess.lock"):
    sleep(60)