PepMiniiso/pylibraries/tendo/singleton.py

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#! /usr/bin/env python
import logging
import os
import sys
import tempfile
if sys.platform != "win32":
import fcntl
class SingleInstanceException(BaseException):
pass
class SingleInstance(object):
"""Class that can be instantiated only once per machine.
If you want to prevent your script from running in parallel just instantiate SingleInstance() class. If is there another instance already running it will throw a `SingleInstanceException`.
>>> import tendo
... me = SingleInstance()
This option is very useful if you have scripts executed by crontab at small amounts of time.
Remember that this works by creating a lock file with a filename based on the full path to the script file.
Providing a flavor_id will augment the filename with the provided flavor_id, allowing you to create multiple singleton instances from the same file. This is particularly useful if you want specific functions to have their own singleton instances.
"""
def __init__(self, flavor_id="", lockfile=""):
self.initialized = False
if lockfile:
self.lockfile = lockfile
else:
basename = os.path.splitext(os.path.abspath(sys.argv[0]))[0].replace(
"/", "-").replace(":", "").replace("\\", "-") + '-%s' % flavor_id + '.lock'
self.lockfile = os.path.normpath(
tempfile.gettempdir() + '/' + basename)
logger.debug("SingleInstance lockfile: " + self.lockfile)
if sys.platform == 'win32':
try:
# file already exists, we try to remove (in case 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 == 13:
logger.error(
"Another instance is already running, quitting.")
raise SingleInstanceException()
print(e.errno)
raise
else: # non Windows
self.fp = open(self.lockfile, 'w')
self.fp.flush()
try:
fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
except IOError:
logger.warning(
"Another instance is already running, quitting.")
raise SingleInstanceException()
self.initialized = True
def __del__(self):
if not self.initialized:
return
try:
if sys.platform == 'win32':
if hasattr(self, 'fd'):
os.close(self.fd)
os.unlink(self.lockfile)
else:
fcntl.lockf(self.fp, fcntl.LOCK_UN)
# os.close(self.fp)
if os.path.isfile(self.lockfile):
os.unlink(self.lockfile)
except Exception as e:
if logger:
logger.warning(e)
else:
print("Unloggable error: %s" % e)
sys.exit(-1)
logger = logging.getLogger("tendo.singleton")