web_server: Log requests to WSGI app

- This is quite useful for debugging even on production machines.

- CherryPy can't be used for logging as grafting a WSGI application bypasses the
usual mechanisms of logging.

- Keep requests for static files turned off in CherryPy as these are not very
useful.

Tests:

- Making a request print an INFO message on the log with method and path after
the /freedombox part. Logs can be seen in systemd journal.

- Requests for static files are not logged.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/web_server.py

@@ -72,8 +72,19 @@ def init():
         'engine.autoreload.match': AUTORELOAD_REGEX,
     })
 
+    def _logging_middleware(application):
+        """A WSGI middleware to log messages before executing them."""
+
+        def _wrapper(environ, start_response):
+            """Log request, then hand control to original app."""
+            logger.info("%s %s", environ['REQUEST_METHOD'],
+                        environ['PATH_INFO'])
+            return application(environ, start_response)
+
+        return _wrapper
+
     application = web_framework.get_wsgi_application()
-    cherrypy.tree.graft(application, cfg.server_dir)
+    cherrypy.tree.graft(_logging_middleware(application), cfg.server_dir)
 
     static_dir = os.path.join(cfg.file_root, 'static')
     _mount_static_directory(static_dir, web_framework.get_static_url())