87 lines
3.1 KiB
Python
87 lines
3.1 KiB
Python
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# -*- coding: iso-8859-1 -*-
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# Copied from: https://github.com/pycontribs/tendo
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# License: PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
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# Author: Sorin Sbarnea
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# Changes: changed logging and formatting
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import sys
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import os
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import errno
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import tempfile
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from .output import out
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class SingleInstance(object):
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"""
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To prevent a script from running in parallel instantiate the
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SingleInstance() class. If is there another instance
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already running it will exit the application with the message
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"Another instance is already running, quitting.",
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returning an error code of -1.
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>>> me = SingleInstance()
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This is very useful to execute scripts by crontab that should only run
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one at a time.
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Note that this works by creating a lock file with a filename based
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on the full path to the script file.
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"""
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def __init__(self, flavor_id="", exit_code=-1):
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"""Create an exclusive lockfile or exit with an error and the given
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exit code."""
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self.initialized = False
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scriptname = os.path.splitext(os.path.abspath(sys.argv[0]))[0]
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lockname = scriptname.replace("/", "-").replace(":", "").replace("\\", "-")
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if flavor_id:
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lockname += "-%s" % flavor_id
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lockname += '.lock'
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tempdir = tempfile.gettempdir()
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self.lockfile = os.path.normpath(os.path.join(tempdir, lockname))
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out.debug("SingleInstance lockfile: " + self.lockfile)
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print(self.lockfile)
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if sys.platform == 'win32':
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try:
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# file already exists, try to remove it in case the previous
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# execution was interrupted
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if os.path.exists(self.lockfile):
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os.unlink(self.lockfile)
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self.fd = os.open(self.lockfile, os.O_CREAT | os.O_EXCL | os.O_RDWR)
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except OSError:
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type, e, tb = sys.exc_info()
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if e.errno == errno.EACCES: # EACCES == 13
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self.exit(exit_code)
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raise
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else: # non Windows
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import fcntl
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self.fp = open(self.lockfile, 'w')
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try:
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fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
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# raises IOError on Python << 3.3, else OSError
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except (IOError, OSError):
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self.exit(exit_code)
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self.initialized = True
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def exit(self, exit_code):
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"""Exit with an error message and the given exit code."""
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out.error("Another instance is already running, quitting.")
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sys.exit(exit_code)
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def __del__(self):
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"""Remove the lock file."""
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if not self.initialized:
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return
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try:
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if sys.platform == 'win32':
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if hasattr(self, 'fd'):
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os.close(self.fd)
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os.unlink(self.lockfile)
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else:
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import fcntl
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fcntl.lockf(self.fp, fcntl.LOCK_UN)
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if os.path.isfile(self.lockfile):
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os.unlink(self.lockfile)
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except StandardError as e:
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out.exception("could not remove lockfile: %s" % e)
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