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PyBitmessage/src/singleinstance.py

92 lines
3.1 KiB

#! /usr/bin/env python
import atexit
import errno
from multiprocessing import Process
import os
import sys
import state
try:
import fcntl # @UnresolvedImport
except:
pass
class singleinstance:
"""
Implements a single instance application by creating a lock file at appdata.
This is based upon the singleton class from tendo https://github.com/pycontribs/tendo
which is under the Python Software Foundation License version 2
"""
def __init__(self, flavor_id="", daemon=False):
self.initialized = False
self.counter = 0
self.daemon = daemon
self.lockPid = None
self.lockfile = os.path.normpath(os.path.join(state.appdata, 'singleton%s.lock' % flavor_id))
if not self.daemon and not state.curses:
# Tells the already running (if any) application to get focus.
import bitmessageqt
bitmessageqt.init()
self.lock()
self.initialized = True
atexit.register(self.cleanup)
def lock(self):
if self.lockPid is None:
self.lockPid = os.getpid()
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 | os.O_TRUNC)
except OSError:
type, e, tb = sys.exc_info()
if e.errno == 13:
print 'Another instance of this application is already running'
sys.exit(-1)
print(e.errno)
raise
else:
pidLine = "%i\n" % self.lockPid
os.write(self.fd, pidLine)
else: # non Windows
self.fp = open(self.lockfile, 'w')
try:
if self.daemon and self.lockPid != os.getpid():
fcntl.lockf(self.fp, fcntl.LOCK_EX) # wait for parent to finish
else:
fcntl.lockf(self.fp, fcntl.LOCK_EX | fcntl.LOCK_NB)
self.lockPid = os.getpid()
except IOError:
print 'Another instance of this application is already running'
sys.exit(-1)
else:
pidLine = "%i\n" % self.lockPid
self.fp.write(pidLine)
self.fp.flush()
def cleanup(self):
if not self.initialized:
return
if self.daemon and self.lockPid == os.getpid():
# these are the two initial forks while daemonizing
return
print "Cleaning up lockfile"
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)
if os.path.isfile(self.lockfile):
os.unlink(self.lockfile)
except Exception, e:
pass