Directories restructered

daemon.py

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+"""
+Generic linux daemon base class for python 3.x.
+
+Original Source:
+https://web.archive.org/web/20131017130434/http://www.jejik.com/articles/2007/02/a_simple_unix_linux_daemon_in_python/
+https://web.archive.org/web/20131017130434/http://www.jejik.com/files/examples/daemon3x.py
+See daemon3x.py in the uplink source tree.
+
+More Information:
+https://franklingu.github.io/programming/2016/03/01/creating-daemon-process-python-example-explanation/
+https://dpbl.wordpress.com/2017/02/12/a-tutorial-on-python-daemon/
+"""
+
+from logging import getLogger
+import sys
+import os
+import time
+import atexit
+import signal
+
+logger = getLogger(__name__)
+
+
+# TODO: Check why pid files are not being deleted when sending the TERM signal
+class Daemon:
+    """
+    A generic daemon class.
+
+    Usage: subclass the daemon class and override the run() method.
+    """
+
+    def __init__(self, pid_file):
+        self.pid_file = pid_file
+
+    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:
+            logger.error('fork #1 failed: {0}\n'.format(err))
+            sys.exit(1)
+
+        # decouple from parent environme
+        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:
+            logger.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.del_pid)
+
+        pid = str(os.getpid())
+        with open(self.pid_file, 'w+') as f:
+            f.write(pid + '\n')
+
+    def del_pid(self):
+        os.remove(self.pid_file)
+
+    def start(self):
+        """
+        Start the daemon.
+        """
+
+        # Check for a pidfile to see if the daemon already runs
+        try:
+            with open(self.pid_file, 'r') as pf:
+                pid = int(pf.read().strip())
+        except IOError:
+            pid = None
+
+        if pid:
+            message = "pid_file {0} already exist. Daemon already running?\n"
+            logger.error(message.format(self.pid_file))
+            sys.exit(1)
+
+        # Start the daemon
+        self.daemonize()
+        self.run()
+
+    def stop(self):
+        """
+        Stop the daemon.
+        """
+
+        # Get the pid from the pidfile
+        try:
+            with open(self.pid_file, 'r') as pf:
+                pid = int(pf.read().strip())
+        except IOError:
+            pid = None
+
+        if not pid:
+            message = "pid_file {0} does not exist. Daemon not running?\n"
+            logger.error(message.format(self.pid_file))
+            # not an error in a restart
+            return
+
+        # 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.pid_file):
+                    os.remove(self.pid_file)
+            else:
+                logger.error(str(err.args))
+                sys.exit(1)
+
+    def restart(self):
+        """
+        Restart the daemon.
+        """
+        self.stop()
+        self.start()
+
+    def run(self):
+        """
+        Override this method when you subclass Daemon.
+        It will be called after the process has been daemonized by
+        start() or restart().
+        """