Implement PID file support in nntp.tiny.daemon

bin/nntp-tiny-server

@@ -6,6 +6,7 @@ import argparse
 from nntp.tiny.config import Config
 from nntp.tiny.db     import Database
 from nntp.tiny.server import Server
+from nntp.tiny.daemon import Daemon
 
 parser = argparse.ArgumentParser(description='Tiny NNTP server')
 parser.add_argument('--daemon', '-d', action='store_true', help='Run NNTP server as daemon in background')
@@ -16,9 +17,6 @@ config = Config.load()
 server = Server(config)
 
 if args.daemon:
-    pid = os.fork()
-
-    if pid > 0:
-        exit(0)
+    Daemon.init(config)
 
 server.run()

lib/nntp/tiny/config.py

@@ -4,11 +4,35 @@ import configparser
 from typing import Optional
 
 class ConfigException(Exception):
-    def __init__(self, path: str):
-        self.path = path
+    pass
+
+class ConfigSectionException(ConfigException):
+    def __init__(self, section: str):
+        self.section = section
 
     def __str__(self):
-        return "Unable to locate file '" + self.path + "'"
+        return "Missing configuration section '%s'" % (
+            self.section
+        )
+
+class ConfigValueException(ConfigException):
+    def __init__(self, section: str, value: str):
+        self.section = section
+        self.value   = value
+
+    def __str__(self):
+        return "Missing configuration value '%s' in section '%s'" % (
+            self.value, self.section
+        )
+
+class ConfigFileException(ConfigException):
+    def __init__(self, paths: list):
+        self.paths = paths
+
+    def __str__(self):
+        return "Unable to locate configuration file in: %s" % (
+            ", ".join(self.paths)
+        )
 
 class Config():
     SEARCH_PATHS = [
@@ -29,7 +53,7 @@ class Config():
             path = Config.find()
             
         if path is None:
-            raise ConfigException(path)
+            raise ConfigFileException(Config.SEARCH_PATHS)
 
         parser = configparser.ConfigParser()
         parser.read(path)

lib/nntp/tiny/daemon.py

@@ -0,0 +1,26 @@
+import os
+import signal
+import configparser
+
+from nntp.tiny.config import (ConfigSectionException,
+                              ConfigValueException)
+
+class Daemon():
+    def init(config: configparser.ConfigParser):
+        if not config.has_section('daemon'):
+            raise ConfigSectionException('daemon')
+
+        if not config.has_option('daemon', 'pidfile'):
+            raise ConfigValueException('daemon', 'pidfile')
+
+        pidfile = config.get('daemon', 'pidfile')
+
+        pid = os.fork()
+
+        if pid > 0:
+            exit(0)
+
+        with open(pidfile, 'w') as fh:
+            print(str(os.getpid()), file=fh)
+
+        signal.signal(signal.SIGTERM, lambda s, f: os.unlink(pidfile))