ahenk deamon class

opt/ahenk/base/deamon/BaseDeamon.py

@@ -0,0 +1,129 @@
+#!/usr/bin/env python
+ 
+import sys, os, time, atexit
+from signal import SIGTERM
+ 
+class BaseDeamon:
+        """
+        A generic daemon class.
+       
+        Usage: subclass the Daemon class and override the run() method
+        """
+        def __init__(self, pidfile, stdin='/dev/null', stdout='/dev/null', stderr='/dev/null'):
+                self.stdin = stdin
+                self.stdout = stdout
+                self.stderr = stderr
+                self.pidfile = pidfile
+       
+        def daemonize(self):
+                """
+                do the UNIX double-fork magic, see Stevens' "Advanced
+                Programming in the UNIX Environment" for details (ISBN 0201563177)
+                http://www.erlenstar.demon.co.uk/unix/faq_2.html#SEC16
+                """
+                try:
+                        pid = os.fork()
+                        if pid > 0:
+                                # exit first parent
+                                sys.exit(0)
+                except OSError, e:
+                        sys.stderr.write("fork #1 failed: %d (%s)\n" % (e.errno, e.strerror))
+                        sys.exit(1)
+       
+                # decouple from parent environment
+                os.chdir("/")
+                os.setsid()
+                os.umask(0)
+       
+                # do second fork
+                try:
+                        pid = os.fork()
+                        if pid > 0:
+                                # exit from second parent
+                                sys.exit(0)
+                except OSError, e:
+                        sys.stderr.write("fork #2 failed: %d (%s)\n" % (e.errno, e.strerror))
+                        sys.exit(1)
+       
+                # redirect standard file descriptors
+                sys.stdout.flush()
+                sys.stderr.flush()
+                si = file(self.stdin, 'r')
+                so = file(self.stdout, 'a+')
+                se = file(self.stderr, 'a+', 0)
+                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())
+                file(self.pidfile,'w+').write("%s\n" % pid)
+       
+        def delpid(self):
+                os.remove(self.pidfile)
+ 
+        def start(self):
+                """
+                Start the daemon
+                """
+                # Check for a pidfile to see if the daemon already runs
+                try:
+                        pf = file(self.pidfile,'r')
+                        pid = int(pf.read().strip())
+                        pf.close()
+                except IOError:
+                        pid = None
+       
+                if pid:
+                        message = "pidfile %s already exist. Daemon already running?\n"
+                        sys.stderr.write(message % self.pidfile)
+                        sys.exit(1)
+               
+                # Start the daemon
+                self.daemonize()
+                self.run()
+ 
+        def stop(self):
+                """
+                Stop the daemon
+                """
+                # Get the pid from the pidfile
+                try:
+                        pf = file(self.pidfile,'r')
+                        pid = int(pf.read().strip())
+                        pf.close()
+                except IOError:
+                        pid = None
+       
+                if not pid:
+                        message = "pidfile %s does not exist. Daemon not running?\n"
+                        sys.stderr.write(message % self.pidfile)
+                        return # not an error in a restart
+ 
+                # Try killing the daemon process       
+                try:
+                        while 1:
+                                os.kill(pid, SIGTERM)
+                                time.sleep(0.1)
+                except OSError, err:
+                        err = str(err)
+                        if err.find("No such process") > 0:
+                                if os.path.exists(self.pidfile):
+                                        os.remove(self.pidfile)
+                        else:
+                                print str(err)
+                                sys.exit(1)
+ 
+        def restart(self):
+                """
+                Restart the daemon
+                """
+                self.stop()
+                self.start()
+ 
+        def run(self):
+                """
+                You should override this method when you subclass Daemon. It will be called after the process has been
+                daemonized by start() or restart().
+                """