Initial import 0.1
authorEfrim <mission@libertalia.lan>
Mon, 31 Jan 2011 09:53:56 +0000 (10:53 +0100)
committerEfrim <mission@libertalia.lan>
Mon, 31 Jan 2011 09:53:56 +0000 (10:53 +0100)
src/daemon.py [new file with mode: 0644]

diff --git a/src/daemon.py b/src/daemon.py
new file mode 100644 (file)
index 0000000..787cb65
--- /dev/null
@@ -0,0 +1,194 @@
+# -*- coding: utf-8 -*-
+
+# Public Domain
+#
+# Copyright 2007, 2009 Sander Marechal <s.marechal@jejik.com>
+# Copyright 2010, 2011 Jack Kaliko <efrim@azylum.org>
+#
+# http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
+
+import atexit
+import os
+import sys
+import time
+from signal import signal, SIGTERM
+
+
+class Daemon(object):
+    """
+    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)
+
+        self.write_pid()
+        # 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())
+
+        atexit.register(self.shutdown)
+        self.signal_management()
+
+    def write_pid(self):
+        # write pidfile
+        if not self.pidfile:
+            return
+        pid = str(os.getpid())
+        try:
+            file(self.pidfile, 'w').write('%s\n' % pid)
+            #except IOError, wpid_err:
+        except Exception, wpid_err:
+            sys.stderr.write(u'Error trying to write pid file to %s: %s\n' %
+                   (unicode(self.pidfile, 'utf-8'), wpid_err))
+            sys.exit(1)
+        atexit.register(self.delpid)
+
+    def signal_management(self):
+        # Declare signal handlers
+        signal(SIGTERM, self.exit_handler)
+
+    def exit_handler(self, signum, frame):
+        sys.exit(1)
+
+    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 foreground(self):
+        """
+        Foreground/debug mode
+        """
+        self.write_pid()
+        atexit.register(self.shutdown)
+        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:
+            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):
+                    message = "Daemon not running? removing pid file %s.\n"
+                    sys.stderr.write(message % self.pidfile)
+                    os.remove(self.pidfile)
+            else:
+                print str(err)
+                sys.exit(1)
+
+    def restart(self):
+        """
+        Restart the daemon
+        """
+        self.stop()
+        self.start()
+
+    def shutdown(self):
+        """
+        You should override this method when you subclass Daemon. It will be
+        called when the process is being stopped.
+        Pay attention:
+        Daemon() uses atexit to call Daemon().shutdown(), as a consequence
+        shutdown and any other functions registered via this module are not
+        called when the program is killed by an un-handled/unknown signal.
+        This is the reason of Daemon().signal_management() existence.
+        """
+
+    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().
+        """
+
+
+def main():
+    pass
+
+# Script starts here
+if __name__ == '__main__':
+    main()
+
+# VIM MODLINE
+# vim: ai ts=4 sw=4 sts=4 expandtab