Handle pidfile properly, redirect stderr in daemon

Handle pidfile creation properly, as part of daemonization process.
Parse config file and setup logging before daemonization.
Redirect stderr to logfile upon daemonization, otherwise numerous
unexpected exceptions get lost.

nfdhcpd

@@ -31,6 +31,7 @@ import traceback
 import subprocess
 
 import daemon
+import daemon.pidlockfile
 import nfqueue
 import pyinotify
 
@@ -826,11 +827,6 @@ if __name__ == "__main__":
 
     opts, args = parser.parse_args()
 
-    if opts.daemonize:
-        d = daemon.DaemonContext()
-        d.umask = 0022
-        d.open()
-
     try:
         config = ConfigObj(opts.config_file, configspec=config_spec)
     except ConfigObjError, err:
@@ -850,16 +846,33 @@ if __name__ == "__main__":
                               ", ".join(section_list))
         sys.exit(1)
 
-    pidfile = open(config["general"]["pidfile"], "w")
-    pidfile.write("%s" % os.getpid())
-    pidfile.close()
-
     logger = logging.getLogger()
     if opts.debug:
         logger.setLevel(logging.DEBUG)
     else:
         logger.setLevel(logging.INFO)
 
+    if opts.daemonize:
+        logfile = os.path.join(config["general"]["logdir"], LOG_FILENAME)
+        handler = logging.handlers.RotatingFileHandler(logfile,
+                                                       maxBytes=2097152)
+    else:
+        handler = logging.StreamHandler()
+
+    handler.setFormatter(logging.Formatter(LOG_FORMAT))
+    logger.addHandler(handler)
+
+    if opts.daemonize:
+        pidfile = daemon.pidlockfile.TimeoutPIDLockFile
+            config["general"]["pidfile"], 10)
+
+        d = daemon.DaemonContext(pidfile=pidfile,
+                                 stdout=handler.stream,
+                                 stderr=handler.stream,
+                                 files_preserve=[handler.stream])
+        d.umask = 0022
+        d.open()
+
     logging.info("Starting up")
 
     proxy_opts = {}
@@ -902,16 +915,6 @@ if __name__ == "__main__":
     capng.capng_change_id(uid.pw_uid, uid.pw_gid,
                           capng.CAPNG_DROP_SUPP_GRP|capng.CAPNG_CLEAR_BOUNDING)
 
-    if opts.daemonize:
-        logfile = os.path.join(config["general"]["logdir"], LOG_FILENAME)
-        handler = logging.handlers.RotatingFileHandler(logfile,
-                                                       maxBytes=2097152)
-    else:
-        handler = logging.StreamHandler()
-
-    handler.setFormatter(logging.Formatter(LOG_FORMAT))
-    logger.addHandler(handler)
-
     logging.info("Ready to serve requests")
     try:
         proxy.serve()