Directory refactoring to be more native to Python.

uplink/daemon.py

@@ -0,0 +1,156 @@
+# Copyright (c) 2022 Johannes Findeisen <you@hanez.org>
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is furnished
+# to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice (including the next
+# paragraph) shall be included in all copies or substantial portions of the
+# Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+# FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS
+# OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
+# WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF
+# OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+
+import atexit
+import os
+import signal
+import sys
+import time
+
+from logging import getLogger
+
+logger = getLogger(__name__)
+
+
+class Daemon:
+    """
+    Usage: subclass the daemon class and override the run() method.
+    """
+
+    def __init__(self, pid_file):
+        self.pid_file = pid_file
+
+    def daemonize(self):
+        """
+        Daemonize the class using the UNIX double fork mechanism.
+        """
+
+        # Do first fork
+        try:
+            pid = os.fork()
+            if pid > 0:
+                # Exit first parent
+                sys.exit(0)
+        except OSError as err:
+            logger.error(str("fork #1 failed: {0}".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:
+            logger.error(str("fork #2 failed: {0}".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?"
+            logger.error(str(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 pid_file
+        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?"
+            logger.error(str(message.format(self.pid_file)))
+            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.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):
+        """
+        You should override this method when you subclass Daemon.
+
+        It will be called after the process has been daemonized by
+        start() or restart().
+        """