| # --------------------------------------------------------------------------- |
| # |
| # Copyright (c) 2005, Greg Stein |
| # |
| # Licensed under the Apache License, Version 2.0 (the "License"); |
| # you may not use this file except in compliance with the License. |
| # You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| # |
| # --------------------------------------------------------------------------- |
| # |
| # This software lives at: |
| # http://gstein.googlecode.com/svn/trunk/python/daemonize.py |
| # |
| |
| import os |
| import signal |
| import sys |
| import time |
| |
| |
| # possible return values from Daemon.daemonize() |
| DAEMON_RUNNING = 'The daemon is running' |
| DAEMON_NOT_RUNNING = 'The daemon is not running' |
| DAEMON_COMPLETE = 'The daemon has completed its operations' |
| DAEMON_STARTED = 'The daemon has been started' |
| |
| |
| class Daemon(object): |
| |
| def __init__(self, logfile, pidfile): |
| self.logfile = logfile |
| self.pidfile = pidfile |
| |
| def foreground(self): |
| "Run in the foreground." |
| ### we should probably create a pidfile. other systems may try to detect |
| ### the pidfile to see if this "daemon" is running. |
| self.setup() |
| self.run() |
| ### remove the pidfile |
| |
| def daemonize_exit(self): |
| try: |
| result = self.daemonize() |
| except (ChildFailed, DaemonFailed), e: |
| # duplicate the exit code |
| sys.exit(e.code) |
| except (ChildTerminatedAbnormally, ChildForkFailed, |
| DaemonTerminatedAbnormally, DaemonForkFailed), e: |
| sys.stderr.write('ERROR: %s\n' % e) |
| sys.exit(1) |
| except ChildResumedIncorrectly: |
| sys.stderr.write('ERROR: continued after receiving unknown signal.\n') |
| sys.exit(1) |
| |
| if result == DAEMON_STARTED or result == DAEMON_COMPLETE: |
| sys.exit(0) |
| elif result == DAEMON_NOT_RUNNING: |
| sys.stderr.write('ERROR: the daemon exited with a success code ' |
| 'without signalling its startup.\n') |
| sys.exit(1) |
| |
| # in original process. daemon is up and running. we're done. |
| |
| def daemonize(self): |
| # fork off a child that can detach itself from this process. |
| try: |
| pid = os.fork() |
| except OSError, e: |
| raise ChildForkFailed(e.errno, e.strerror) |
| |
| if pid > 0: |
| # we're in the parent. let's wait for the child to finish setting |
| # things up -- on our exit, we want to ensure the child is accepting |
| # connections. |
| cpid, status = os.waitpid(pid, 0) |
| assert pid == cpid |
| if os.WIFEXITED(status): |
| code = os.WEXITSTATUS(status) |
| if code: |
| raise ChildFailed(code) |
| return DAEMON_RUNNING |
| |
| # the child did not exit cleanly. |
| raise ChildTerminatedAbnormally(status) |
| |
| # we're in the child. |
| |
| # decouple from the parent process |
| os.chdir('/') |
| os.umask(0) |
| os.setsid() |
| |
| # remember this pid so the second child can signal it. |
| thispid = os.getpid() |
| |
| # register a signal handler so the SIGUSR1 doesn't stop the process. |
| # this object will also record whether if got signalled. |
| daemon_accepting = SignalCatcher(signal.SIGUSR1) |
| |
| # if the daemon process exits before sending SIGUSR1, then we need to see |
| # the problem. trap SIGCHLD with a SignalCatcher. |
| daemon_exit = SignalCatcher(signal.SIGCHLD) |
| |
| # perform the second fork |
| try: |
| pid = os.fork() |
| except OSError, e: |
| raise DaemonForkFailed(e.errno, e.strerror) |
| |
| if pid > 0: |
| # in the parent. |
| |
| # we want to wait for the daemon to signal that it has created and |
| # bound the socket, and is (thus) ready for connections. if the |
| # daemon improperly exits before serving, we'll see SIGCHLD and the |
| # .pause will return. |
| ### we should add a timeout to this. allow an optional parameter to |
| ### specify the timeout, in case it takes a long time to start up. |
| signal.pause() |
| |
| if daemon_exit.signalled: |
| # reap the daemon process, getting its exit code. bubble it up. |
| cpid, status = os.waitpid(pid, 0) |
| assert pid == cpid |
| if os.WIFEXITED(status): |
| code = os.WEXITSTATUS(status) |
| if code: |
| raise DaemonFailed(code) |
| return DAEMON_NOT_RUNNING |
| |
| # the daemon did not exit cleanly. |
| raise DaemonTerminatedAbnormally(status) |
| |
| if daemon_accepting.signalled: |
| # the daemon is up and running, so save the pid and return success. |
| if self.pidfile: |
| open(self.pidfile, 'w').write('%d\n' % pid) |
| return DAEMON_STARTED |
| |
| # some other signal popped us out of the pause. the daemon might not |
| # be running. |
| raise ChildResumedIncorrectly() |
| |
| # we're a deamon now. get rid of the final remnants of the parent. |
| # start by restoring default signal handlers |
| signal.signal(signal.SIGUSR1, signal.SIG_DFL) |
| signal.signal(signal.SIGCHLD, signal.SIG_DFL) |
| sys.stdout.flush() |
| sys.stderr.flush() |
| si = open('/dev/null', 'r') |
| so = open(self.logfile, 'a+') |
| se = open(self.logfile, 'a+', 0) # unbuffered |
| os.dup2(si.fileno(), sys.stdin.fileno()) |
| os.dup2(so.fileno(), sys.stdout.fileno()) |
| os.dup2(se.fileno(), sys.stderr.fileno()) |
| # note: we could not inline the open() calls. after the fileno() completed, |
| # the file would be closed, making the fileno invalid. gotta hold them |
| # open until now: |
| si.close() |
| so.close() |
| se.close() |
| |
| # TEST: don't release the parent immediately. the whole parent stack |
| # should pause along with this sleep. |
| #time.sleep(10) |
| |
| # everything is set up. call the initialization function. |
| self.setup() |
| |
| # sleep for one second before signalling. we want to make sure the |
| # parent has called signal.pause() |
| ### we should think of a better wait around the race condition. |
| time.sleep(1) |
| |
| # okay. the daemon is ready. signal the parent to tell it we're set. |
| os.kill(thispid, signal.SIGUSR1) |
| |
| # start the daemon now. |
| self.run() |
| |
| # The daemon is shutting down, so toss the pidfile. |
| try: |
| os.remove(self.pidfile) |
| except OSError: |
| pass |
| |
| return DAEMON_COMPLETE |
| |
| def setup(self): |
| raise NotImplementedError |
| |
| def run(self): |
| raise NotImplementedError |
| |
| |
| class SignalCatcher(object): |
| def __init__(self, signum): |
| self.signalled = False |
| signal.signal(signum, self.sig_handler) |
| |
| def sig_handler(self, signum, frame): |
| self.signalled = True |
| |
| |
| class ChildTerminatedAbnormally(Exception): |
| "The child process terminated abnormally." |
| def __init__(self, status): |
| Exception.__init__(self, status) |
| self.status = status |
| def __str__(self): |
| return 'child terminated abnormally (0x%04x)' % self.status |
| |
| class ChildFailed(Exception): |
| "The child process exited with a failure code." |
| def __init__(self, code): |
| Exception.__init__(self, code) |
| self.code = code |
| def __str__(self): |
| return 'child failed with exit code %d' % self.code |
| |
| class ChildForkFailed(Exception): |
| "The child process could not be forked." |
| def __init__(self, errno, strerror): |
| Exception.__init__(self, errno, strerror) |
| self.errno = errno |
| self.strerror = strerror |
| def __str__(self): |
| return 'child fork failed with error %d (%s)' % self.args |
| |
| class ChildResumedIncorrectly(Exception): |
| "The child resumed its operation incorrectly." |
| |
| class DaemonTerminatedAbnormally(Exception): |
| "The daemon process terminated abnormally." |
| def __init__(self, status): |
| Exception.__init__(self, status) |
| self.status = status |
| def __str__(self): |
| return 'daemon terminated abnormally (0x%04x)' % self.status |
| |
| class DaemonFailed(Exception): |
| "The daemon process exited with a failure code." |
| def __init__(self, code): |
| Exception.__init__(self, code) |
| self.code = code |
| def __str__(self): |
| return 'daemon failed with exit code %d' % self.code |
| |
| class DaemonForkFailed(Exception): |
| "The daemon process could not be forked." |
| def __init__(self, errno, strerror): |
| Exception.__init__(self, errno, strerror) |
| self.errno = errno |
| self.strerror = strerror |
| def __str__(self): |
| return 'daemon fork failed with error %d (%s)' % self.args |
