Add metrics to track the cpu on the main thread consumed by each type…

… of request

synapse/http/server.py

@@ -53,6 +53,14 @@
     labels=["method", "servlet"]
 )
 
+response_ru_utime = metrics.register_distribution(
+    "response_ru_utime", labels=["method", "servlet"]
+)
+
+response_ru_stime = metrics.register_distribution(
+    "response_ru_stime", labels=["method", "servlet"]
+)
+
 _next_request_id = 0
 
 
@@ -221,6 +229,15 @@ def _async_render(self, request):
                 self.clock.time_msec() - start, request.method, servlet_classname
             )
 
+            try:
+                context = LoggingContext.current_context()
+                ru_utime, ru_stime = context.get_resource_usage()
+
+                response_ru_utime.inc_by(ru_utime, request.method, servlet_classname)
+                response_ru_stime.inc_by(ru_stime, request.method, servlet_classname)
+            except:
+                pass
+
             return
 
         # Huh. No one wanted to handle that? Fiiiiiine. Send 400.