first

daemon/SimpleDaemon.py

@@ -0,0 +1,194 @@
+"""Generic linux daemon base class for python 3.x."""
+
+import sys, os, time, atexit, signal, logging
+
+
+class Daemon:
+    """A generic daemon class.
+
+    Usage: subclass the daemon class and override the run() method."""
+
+    def __init__(self, pidfile, error_log_file='/dev/null'):
+        self.logging = logging
+        self.logging.basicConfig(filename=error_log_file, filemode='w',
+                                 format='%(name)s - %(levelname)s - %(message)s\n')
+        self.logging.getLogger().addHandler(logging.StreamHandler(sys.stdout))
+        self.error_log_file = error_log_file
+        self.pidfile = pidfile
+        self.commands = {}
+
+    def __enter__(self):
+        self.base_commands()
+        self.reg_command()
+
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        pass
+
+    def daemonize(self):
+        """Deamonize class. UNIX double fork mechanism."""
+
+        try:
+            pid = os.fork()
+            if pid > 0:
+                # exit first parent
+                sys.exit(0)
+        except OSError as err:
+            sys.stderr.write('fork #1 failed: {0}\n'.format(err))
+            self.logging.error('fork #1 failed: {0}\n'.format(err))
+            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 as err:
+            sys.stderr.write('fork #2 failed: {0}\n'.format(err))
+            self.logging.error('fork #2 failed: {0}\n'.format(err))
+            sys.exit(1)
+
+        # redirect standard file descriptors
+        sys.stdout.flush()
+        sys.stderr.flush()
+        si = open(os.devnull, 'r')
+        so = open(os.devnull, 'a+')
+        se = open(os.devnull, 'a+')
+
+        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 start(self):
+        """Start the daemon."""
+        self.logging.info("Start")
+
+        # Check for a pidfile to see if the daemon already runs
+        try:
+            with open(self.pidfile, 'r') as pf:
+
+                pid = int(pf.read().strip())
+        except IOError:
+            pid = None
+
+        if pid:
+            message = "pidfile {0} already exist. " + \
+                      "Daemon already running?\n"
+            sys.stderr.write(message.format(self.pidfile))
+            self.logging.error(message.format(self.pidfile))
+            sys.exit(1)
+
+        # Start the daemon
+        self.daemonize()
+        self.run()
+
+    def stop(self):
+        """Stop the daemon."""
+        self.logging.info("Stop")
+
+        # Get the pid from the pidfile
+        try:
+            with open(self.pidfile, 'r') as pf:
+                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))
+            self.logging.error(message.format(self.pidfile))
+            return  # not an error in a restart
+
+        # Try killing the daemon process
+        try:
+            while 1:
+                os.kill(pid, signal.SIGTERM)
+                time.sleep(0.1)
+        except OSError as err:
+            e = str(err.args)
+            if e.find("No such process") > 0:
+                if os.path.exists(self.pidfile):
+                    os.remove(self.pidfile)
+            else:
+                print(str(err.args))
+                sys.exit(1)
+
+    def restart(self):
+        """Restart the daemon."""
+        self.logging.info("Restart")
+        self.stop()
+        self.start()
+
+    def status(self):
+        print("Status")
+        try:
+            with open(self.pidfile, 'r') as pf:
+
+                pid = int(pf.read().strip())
+        except IOError:
+            pid = None
+
+        if pid:
+            print("Process started, pid %d" % pid)
+        else:
+            print("Process is not running")
+
+    def console_stdout(self):
+        sys.stdout = sys.__stdout__
+        print(123)
+
+    def process_command(self):
+        if len(sys.argv) > 1:
+            command = sys.argv[1]
+            handler = self.get_command_handler(command)
+            if handler:
+                handler()
+            else:
+                print("Unknown command: %s" % command)
+        else:
+            print("usage: %s start|stop|restart|status" % sys.argv[0])
+            sys.exit(2)
+
+    def base_commands(self):
+        self.add_command('start', self.start)
+        self.add_command('stop', self.stop)
+        self.add_command('restart', self.restart)
+        self.add_command('status', self.status)
+        self.add_command('console_stdout', self.console_stdout)
+
+    def add_command(self, command, handler):
+        if command not in self.commands:
+            self.commands[command] = handler
+
+    def get_command_handler(self, command):
+        if command in self.commands:
+            return self.commands[command]
+
+        return None
+
+    def reg_command(self):
+        pass
+
+    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()."""