Importing changeset from gns3dms repo

gns3dms/modules/daemon.py

@@ -7,38 +7,38 @@ class daemon:
 
     Usage: subclass the daemon class and override the run() method."""
 
-    def __init__(self, pidfile, options): 
+    def __init__(self, pidfile, options):
         self.pidfile = pidfile
         self.options = options
-    
+
     def daemonize(self):
         """Deamonize class. UNIX double fork mechanism."""
 
-        try: 
-            pid = os.fork() 
+        try:
+            pid = os.fork()
             if pid > 0:
                 # exit first parent
-                sys.exit(0) 
-        except OSError as err: 
+                sys.exit(0)
+        except OSError as err:
             sys.stderr.write('fork #1 failed: {0}\n'.format(err))
             sys.exit(1)
-    
+
         # decouple from parent environment
-        os.chdir('/') 
-        os.setsid() 
-        os.umask(0) 
-    
+        os.chdir('/')
+        os.setsid()
+        os.umask(0)
+
         # do second fork
-        try: 
-            pid = os.fork() 
+        try:
+            pid = os.fork()
             if pid > 0:
 
                 # exit from second parent
-                sys.exit(0) 
-        except OSError as err: 
+                sys.exit(0)
+        except OSError as err:
             sys.stderr.write('fork #2 failed: {0}\n'.format(err))
-            sys.exit(1) 
-    
+            sys.exit(1)
+
         # redirect standard file descriptors
         sys.stdout.flush()
         sys.stderr.flush()
@@ -49,17 +49,26 @@ class daemon:
         os.dup2(si.fileno(), sys.stdin.fileno())
         os.dup2(so.fileno(), sys.stdout.fileno())
         os.dup2(se.fileno(), sys.stderr.fileno())
-    
+
         # write pidfile
         atexit.register(self.delpid)
 
         pid = str(os.getpid())
         with open(self.pidfile,'w+') as f:
             f.write(pid + '\n')
-    
+
     def delpid(self):
         os.remove(self.pidfile)
 
+    def check_pid(self, pid):
+        """ Check For the existence of a unix pid. """
+        try:
+            os.kill(pid, 0)
+        except OSError:
+            return False
+        else:
+            return True
+
     def start(self):
         """Start the daemon."""
 
@@ -70,13 +79,19 @@ class daemon:
                 pid = int(pf.read().strip())
         except IOError:
             pid = None
-    
+
         if pid:
-            message = "pidfile {0} already exist. " + \
-                    "Daemon already running?\n"
+            pid_exist = self.check_pid(pid)
+
+            if pid_exist:
+                message = "Already running: %s\n" % (pid)
+                sys.stderr.write(message)
+                sys.exit(1)
+            else:
+                message = "pidfile {0} already exist. " + \
+                    "but process is dead\n"
             sys.stderr.write(message.format(self.pidfile))
-            sys.exit(1)
-        
+
         # Start the daemon
         self.daemonize()
         self.run()
@@ -90,14 +105,14 @@ class daemon:
                 pid = int(pf.read().strip())
         except IOError:
             pid = None
-    
+
         if not pid:
             message = "pidfile {0} does not exist. " + \
                     "Daemon not running?\n"
             sys.stderr.write(message.format(self.pidfile))
             return # not an error in a restart
 
-        # Try killing the daemon process    
+        # Try killing the daemon process
         try:
             while 1:
                 os.kill(pid, signal.SIGTERM)
@@ -118,6 +133,6 @@ class daemon:
 
     def run(self):
         """You should override this method when you subclass Daemon.
-        
-        It will be called after the process has been daemonized by 
+
+        It will be called after the process has been daemonized by
         start() or restart()."""