Create pid file to avoid having two daemons.

ospd/main.py

@@ -22,10 +22,14 @@
 
 import os
 import sys
+import atexit
+import signal
+
+from functools import partial
 
 from typing import Type, Optional
 
-from ospd.misc import go_to_background
+from ospd.misc import go_to_background, create_pid, remove_pidfile
 from ospd.ospd import OSPDaemon
 from ospd.parser import create_parser, ParserType
 from ospd.server import TlsServer, UnixSocketServer
@@ -128,11 +132,20 @@ def main(
         print_version(daemon)
         sys.exit()
 
-    daemon.init()
-
     if not args.foreground:
         go_to_background()
 
+    if not create_pid(args.pid_file):
+        sys.exit()
+
+    # Set signal handler and cleanup
+    atexit.register(remove_pidfile, pidfile=args.pid_file)
+    signal.signal(
+        signal.SIGTERM, partial(remove_pidfile, args.pid_file)
+    )
+
+    daemon.init()
+
     if not daemon.check():
         return 1
 

ospd/misc.py

@@ -30,6 +30,7 @@
 
 from enum import Enum
 from collections import OrderedDict
+from pathlib import Path
 
 from ospd.network import target_str_to_list
 
@@ -408,3 +409,31 @@ def go_to_background():
     except OSError as errmsg:
         LOGGER.error('Fork failed: %s', errmsg)
         sys.exit(1)
+
+def create_pid(pidfile):
+    """ Check if there is an already running daemon and creates the pid file.
+    Otherwise gives an error. """
+
+    pid = str(os.getpid())
+
+    if Path(pidfile).is_file():
+        LOGGER.error("There is an already running process.")
+        return False
+
+    try:
+        with open(pidfile, 'w') as f:
+            f.write(pid)
+    except (FileNotFoundError, PermissionError) as e:
+        msg = "Failed to create pid file %s. %s" % (os.path.dirname(pidfile), e)
+        LOGGER.error(msg)
+        return False
+
+    return True
+
+def remove_pidfile(pidfile, signum=None, frame=None):
+    """ Removes the pidfile before ending the daemon. """
+    pidpath = Path(pidfile)
+    if pidpath.is_file():
+        LOGGER.debug("Finishing daemon process")
+        pidpath.unlink()
+        sys.exit()

ospd/parser.py

@@ -33,6 +33,7 @@
 DEFAULT_UNIX_SOCKET_MODE = "0o700"
 DEFAULT_CONFIG_PATH = "~/.config/ospd.conf"
 DEFAULT_UNIX_SOCKET_PATH = "/tmp/ospd.sock"
+DEFAULT_PID_PATH = "/run/ospd/ospd.pid"
 
 ParserType = argparse.ArgumentParser
 Arguments = argparse.Namespace
@@ -78,6 +79,11 @@ def __init__(self, description):
             default=DEFAULT_UNIX_SOCKET_PATH,
             help='Unix file socket to listen on. Default: %(default)s',
         )
+        parser.add_argument(
+            '--pid-file',
+            default=DEFAULT_PID_PATH,
+            help='Unix file socket to listen on.'
+        )
 
         parser.add_argument(
             '-m',