11 PID_FILE = '/var/run/node_mgr.pid'
13 def as_daemon_thread(run):
14 """Call function <run> with no arguments in its own thread."""
15 thr = threading.Thread(target=run)
19 def close_nonstandard_fds():
20 """Close all open file descriptors other than 0, 1, and 2."""
22 for fd in range(3, os.sysconf(_SC_OPEN_MAX)):
24 except OSError: pass # most likely an fd that isn't open
26 # after http://www.erlenstar.demon.co.uk/unix/faq_2.html
28 """Daemonize the current process."""
29 if os.fork() != 0: os._exit(0)
31 if os.fork() != 0: os._exit(0)
34 devnull = os.open(os.devnull, os.O_RDWR)
35 for fd in range(3): os.dup2(devnull, fd)
38 """Return a deep copy of obj."""
39 return cPickle.loads(cPickle.dumps(obj, -1))
41 def fork_as(su, function, *args):
42 """fork(), cd / to avoid keeping unused directories open, close all nonstandard file descriptors (to avoid capturing open sockets), fork() again (to avoid zombies) and call <function> with arguments <args> in the grandchild process. If <su> is not None, set our group and user ids appropriately in the child process."""
47 close_nonstandard_fds()
48 pw_ent = pwd.getpwnam(su)
52 if child_pid == 0: function(*args)
54 os.seteuid(os.getuid()) # undo su so we can write the log file
55 os.setegid(os.getgid())
58 else: os.waitpid(child_pid, 0)
61 """We use a pid file to ensure that only one copy of NM is running at a given time. If successful, this function will write a pid file containing the pid of the current process. The return value is the pid of the other running process, or None otherwise."""
63 if os.access(PID_FILE, os.F_OK): # check for a pid file
64 handle = open(PID_FILE) # pid file exists, read it
65 other_pid = int(handle.read())
67 # check for a process with that pid by sending signal 0
68 try: os.kill(other_pid, 0)
70 if e.errno == errno.ESRCH: other_pid = None # doesn't exist
71 else: raise # who knows
73 # write a new pid file
74 write_file(PID_FILE, lambda f: f.write(str(os.getpid())))
77 def write_file(filename, do_write):
78 """Write file <filename> atomically by opening a temporary file, using <do_write> to write that file, and then renaming the temporary file."""
79 os.rename(write_temp_file(do_write), filename)
81 def write_temp_file(do_write):
82 fd, temporary_filename = tempfile.mkstemp()
83 f = os.fdopen(fd, 'w')
86 return temporary_filename