84 lines
3 KiB
Python
84 lines
3 KiB
Python
# SPDX-License-Identifier: PSF-2.0
|
|
# Copied from: https://github.com/pycontribs/tendo
|
|
# Author: Sorin Sbarnea
|
|
# Changes: changed logging and formatting
|
|
import sys
|
|
import os
|
|
import errno
|
|
import tempfile
|
|
from .output import out
|
|
|
|
|
|
class SingleInstance(object):
|
|
"""
|
|
To prevent a script from running in parallel instantiate the
|
|
SingleInstance() class. If is there another instance
|
|
already running it will exit the application with the message
|
|
"Another instance is already running, quitting.",
|
|
returning an error code of -1.
|
|
|
|
>>> me = SingleInstance()
|
|
|
|
This is very useful to execute scripts by crontab that should only run
|
|
one at a time.
|
|
|
|
Note that this works by creating a lock file with a filename based
|
|
on the full path to the script file.
|
|
"""
|
|
|
|
def __init__(self, flavor_id="", exit_code=-1):
|
|
"""Create an exclusive lockfile or exit with an error and the given
|
|
exit code."""
|
|
self.initialized = False
|
|
scriptname = os.path.splitext(os.path.realpath(sys.argv[0]))[0]
|
|
lockname = scriptname.replace("/", "-").replace(":", "").replace("\\", "-")
|
|
if flavor_id:
|
|
lockname += "-%s" % flavor_id
|
|
lockname += '.lock'
|
|
tempdir = tempfile.gettempdir()
|
|
self.lockfile = os.path.normpath(os.path.join(tempdir, lockname))
|
|
out.debug("SingleInstance lockfile: " + self.lockfile)
|
|
if sys.platform == 'win32':
|
|
try:
|
|
# file already exists, try to remove it in case the previous
|
|
# execution was interrupted
|
|
if os.path.exists(self.lockfile):
|
|
os.unlink(self.lockfile)
|
|
self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
|
|
except OSError:
|
|
type, e, tb = sys.exc_info()
|
|
if e.errno == errno.EACCES: # EACCES == 13
|
|
self.exit(exit_code)
|
|
raise
|
|
else: # non Windows
|
|
import fcntl
|
|
self.fp = open(self.lockfile, 'w')
|
|
try:
|
|
fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
|
|
# raises IOError on Python << 3.3, else OSError
|
|
except OSError:
|
|
self.exit(exit_code)
|
|
self.initialized = True
|
|
|
|
def exit(self, exit_code):
|
|
"""Exit with an error message and the given exit code."""
|
|
out.error("Another instance is already running, quitting.")
|
|
sys.exit(exit_code)
|
|
|
|
def __del__(self):
|
|
"""Remove the lock file."""
|
|
if not self.initialized:
|
|
return
|
|
try:
|
|
if sys.platform == 'win32':
|
|
if hasattr(self, 'fd'):
|
|
os.close(self.fd)
|
|
os.unlink(self.lockfile)
|
|
else:
|
|
import fcntl
|
|
fcntl.lockf(self.fp, fcntl.LOCK_UN)
|
|
if os.path.isfile(self.lockfile):
|
|
os.unlink(self.lockfile)
|
|
except Exception as e:
|
|
out.exception("could not remove lockfile: %s" % e)
|