Either --state-file or logfile arguments must be specified.

apachedex/__init__.py

@@ -1304,6 +1304,9 @@ def main():
       'ignored. Useful to exclude monitoring systems.')
 
   args = parser.parse_args()
+  if not args.logfile and not args.state_file:
+    parser.error('Either --state-file or logfile arguments '
+                 'must be specified.')
   if DURATION_US_FORMAT in args.logformat:
     getDuration = lambda x: int(x.group('duration'))
   elif DURATION_S_FORMAT in args.logformat: