Lot of refactoring to prepare project renaming to my old and similiar project linspector

monipy/core/daemon.py

@@ -0,0 +1,147 @@
+"""
+This file is part of monipy (https://hanez.org/monipy/)
+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('monipy')
+
+
+class Daemon:
+    # 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 pid file.
+        atexit.register(self.delete_pid)
+
+        pid = str(os.getpid())
+        with open(self.__pid_file, 'w+') as f:
+            f.write(pid + '\n')
+
+    def delete_pid(self):
+        os.remove(self.__pid_file)
+
+    def start(self):
+        # start the daemon. check for a pidfile to see if the daemon already runs before.
+
+        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().
+        """