Add "dc_id" to metrics

src/mtp_handler.erl

@@ -331,7 +331,7 @@ handle_upstream_header(DcId, S) ->
         {ok, Sock} ->
             AddrStr = inet:ntoa(Addr),
             mtp_metric:count_inc([?APP, out_connect_ok, total], 1,
-                             #{labels => [AddrStr]}),
+                             #{labels => [DcId, AddrStr]}),
             lager:info("Connected to ~s:~p", [AddrStr, Port]),
             down_handshake1(S#state{down_sock = Sock});
         {error, Reason} = Err ->

src/mtp_metric.erl

@@ -123,7 +123,7 @@ active_metrics() ->
 
      {count, [?APP, out_connect_ok, total],
       "Proxy out connections",
-      #{labels => [listener, dc]}},
+      #{labels => [listener, dc_id, addr]}},
      {count, [?APP, out_connect_error, total],
       "Proxy out connect errors",
       #{labels => [listener, reason]}},