Source Code for Module linspector.lib.core.daemon

  1  import sys 
  2  import os 
  3  import time 
  4  import atexit 
  5  from signal import SIGTERM 
  6   
  7   
  8 -class Daemon: 
  9      """ 
 10      A generic daemon class. 
 11   
 12      Usage: subclass the Daemon class and override the run() method 
 13      """ 
 14   
 15 -    def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'): 
 16          self.stdin = stdin 
 17          self.stdout = stdout 
 18          self.stderr = stderr 
 19          self.pidfile = pidfile 
 20   
 21 -    def daemonize(self): 
 22          """ 
 23          do the UNIX double-fork magic, see Stevens' "Advanced 
 24          Programming in the UNIX Environment" for details (ISBN 0201563177) 
 25          http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16 
 26          """ 
 27          try: 
 28              pid = os.fork() 
 29              if pid > 0: 
 30                  # exit first parent 
 31                  sys.exit(0) 
 32          except OSError, e: 
 33              sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror)) 
 34              sys.exit(1) 
 35   
 36          # decouple from parent environment 
 37          os.chdir("/") 
 38          os.setsid() 
 39          os.umask(0) 
 40   
 41          # do second fork 
 42          try: 
 43              pid = os.fork() 
 44              if pid > 0: 
 45                  # exit from second parent 
 46                  sys.exit(0) 
 47          except OSError, e: 
 48              sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror)) 
 49              sys.exit(1) 
 50   
 51          # redirect standard file descriptors 
 52          sys.stdout.flush() 
 53          sys.stderr.flush() 
 54          si = file(self.stdin, 'r') 
 55          so = file(self.stdout, 'a+') 
 56          se = file(self.stderr, 'a+', 0) 
 57          os.dup2(si.fileno(), sys.stdin.fileno()) 
 58          os.dup2(so.fileno(), sys.stdout.fileno()) 
 59          os.dup2(se.fileno(), sys.stderr.fileno()) 
 60   
 61          # write pidfile 
 62          atexit.register(self.delpid) 
 63          pid = str(os.getpid()) 
 64          file(self.pidfile, 'w+').write("%s\n" % pid) 
 65   
 66 -    def delpid(self): 
 67          os.remove(self.pidfile) 
 68   
 69 -    def start(self): 
 70          """ 
 71          Start the daemon 
 72          """ 
 73          # Check for a pidfile to see if the daemon already runs 
 74          try: 
 75              pf = file(self.pidfile, 'r') 
 76              pid = int(pf.read().strip()) 
 77              pf.close() 
 78          except IOError: 
 79              pid = None 
 80   
 81          if pid: 
 82              message = "pidfile %s already exist. daemon already running?\n" 
 83              sys.stderr.write(message % self.pidfile) 
 84              sys.exit(1) 
 85   
 86          # Start the daemon 
 87          self.daemonize() 
 88          self.run() 
 89   
 90 -    def stop(self): 
 91          """ 
 92          Stop the daemon 
 93          """ 
 94          # Get the pid from the pidfile 
 95          try: 
 96              pf = file(self.pidfile, 'r') 
 97              pid = int(pf.read().strip()) 
 98              pf.close() 
 99          except IOError: 
100              pid = None 
101   
102          if not pid: 
103              message = "pidfile %s does not exist. daemon not running?\n" 
104              sys.stderr.write(message % self.pidfile) 
105              return # not an error in a restart 
106   
107          # Try killing the daemon process 
108          try: 
109              while 1: 
110                  os.kill(pid, SIGTERM) 
111                  time.sleep(0.1) 
112          except OSError, err: 
113              err = str(err) 
114              if err.find("No such process") > 0: 
115                  if os.path.exists(self.pidfile): 
116                      os.remove(self.pidfile) 
117              else: 
118                  print str(err) 
119                  sys.exit(1) 
120   
121 -    def restart(self): 
122          """ 
123          Restart the daemon 
124          """ 
125          self.stop() 
126          self.start() 
127   
128 -    def run(self): 
129          """ 
130          You should override this method when you subclass Daemon. 
131          It will be called after the process has been 
132          daemonized by start() or restart(). 
133          """ 
134