refactor(emqx_opentelemetry): pass only channel info to trace functions

apps/emqx/src/emqx_channel.erl

@@ -399,7 +399,12 @@ handle_in(?PACKET(_), Channel = #channel{conn_state = ConnState}) when
 handle_in(Packet = ?PUBLISH_PACKET(_QoS), Channel) ->
     case emqx_packet:check(Packet) of
         ok ->
-            emqx_external_trace:trace_process_publish(Packet, Channel, fun process_publish/2);
+            emqx_external_trace:trace_process_publish(
+                Packet,
+                %% More info can be added in future, but for now only clientid is used
+                trace_info(Channel),
+                fun(PacketWithTrace) -> process_publish(PacketWithTrace, Channel) end
+            );
         {error, ReasonCode} ->
             handle_out(disconnect, ReasonCode, Channel)
     end;
@@ -924,7 +929,7 @@ handle_deliver(
     NSession = emqx_session_mem:enqueue(ClientInfo, Messages, Session),
     {ok, Channel#channel{session = NSession}};
 handle_deliver(Delivers, Channel) ->
-    Delivers1 = emqx_external_trace:start_trace_send(Delivers, Channel),
+    Delivers1 = emqx_external_trace:start_trace_send(Delivers, trace_info(Channel)),
     do_handle_deliver(Delivers1, Channel).
 
 do_handle_deliver(
@@ -1435,6 +1440,10 @@ overload_protection(_, #channel{clientinfo = #{zone := Zone}}) ->
     emqx_olp:backoff(Zone),
     ok.
 
+trace_info(Channel) ->
+    %% More info can be added in future, but for now only clientid is used
+    maps:from_list(info([clientid], Channel)).
+
 %%--------------------------------------------------------------------
 %% Enrich MQTT Connect Info
 

apps/emqx/src/emqx_external_trace.erl

@@ -15,18 +15,20 @@
 %%--------------------------------------------------------------------
 -module(emqx_external_trace).
 
--callback trace_process_publish(Packet, Channel, fun((Packet, Channel) -> Res)) -> Res when
+-callback trace_process_publish(Packet, ChannelInfo, fun((Packet) -> Res)) -> Res when
     Packet :: emqx_types:packet(),
-    Channel :: emqx_channel:channel(),
+    ChannelInfo :: channel_info(),
     Res :: term().
 
--callback start_trace_send(list(emqx_types:deliver()), emqx_channel:channel()) ->
+-callback start_trace_send(list(emqx_types:deliver()), channel_info()) ->
     list(emqx_types:deliver()).
 
 -callback end_trace_send(emqx_types:packet() | [emqx_types:packet()]) -> ok.
 
 -callback event(EventName :: term(), Attributes :: term()) -> ok.
 
+-type channel_info() :: #{atom() => _}.
+
 -export([
     provider/0,
     register_provider/1,
@@ -38,6 +40,8 @@
     event/2
 ]).
 
+-export_type([channel_info/0]).
+
 -define(PROVIDER, {?MODULE, trace_provider}).
 
 -define(with_provider(IfRegistered, IfNotRegistered),
@@ -79,17 +83,17 @@ provider() ->
 %% trace API
 %%--------------------------------------------------------------------
 
--spec trace_process_publish(Packet, Channel, fun((Packet, Channel) -> Res)) -> Res when
+-spec trace_process_publish(Packet, ChannelInfo, fun((Packet) -> Res)) -> Res when
     Packet :: emqx_types:packet(),
-    Channel :: emqx_channel:channel(),
+    ChannelInfo :: channel_info(),
     Res :: term().
-trace_process_publish(Packet, Channel, ProcessFun) ->
-    ?with_provider(?FUNCTION_NAME(Packet, Channel, ProcessFun), ProcessFun(Packet, Channel)).
+trace_process_publish(Packet, ChannelInfo, ProcessFun) ->
+    ?with_provider(?FUNCTION_NAME(Packet, ChannelInfo, ProcessFun), ProcessFun(Packet)).
 
--spec start_trace_send(list(emqx_types:deliver()), emqx_channel:channel()) ->
+-spec start_trace_send(list(emqx_types:deliver()), channel_info()) ->
     list(emqx_types:deliver()).
-start_trace_send(Delivers, Channel) ->
-    ?with_provider(?FUNCTION_NAME(Delivers, Channel), Delivers).
+start_trace_send(Delivers, ChannelInfo) ->
+    ?with_provider(?FUNCTION_NAME(Delivers, ChannelInfo), Delivers).
 
 -spec end_trace_send(emqx_types:packet() | [emqx_types:packet()]) -> ok.
 end_trace_send(Packets) ->

apps/emqx_opentelemetry/src/emqx_otel_trace.erl

@@ -94,17 +94,17 @@ stop() ->
 %% trace API
 %%--------------------------------------------------------------------
 
--spec trace_process_publish(Packet, Channel, fun((Packet, Channel) -> Res)) -> Res when
+-spec trace_process_publish(Packet, ChannelInfo, fun((Packet) -> Res)) -> Res when
     Packet :: emqx_types:packet(),
-    Channel :: emqx_channel:channel(),
+    ChannelInfo :: emqx_external_trace:channel_info(),
     Res :: term().
-trace_process_publish(Packet, Channel, ProcessFun) ->
+trace_process_publish(Packet, ChannelInfo, ProcessFun) ->
     case maybe_init_ctx(Packet) of
         false ->
-            ProcessFun(Packet, Channel);
+            ProcessFun(Packet);
         RootCtx ->
             RootCtx1 = otel_ctx:set_value(RootCtx, ?IS_ENABLED, true),
-            Attrs = maps:merge(packet_attributes(Packet), channel_attributes(Channel)),
+            Attrs = maps:merge(packet_attributes(Packet), channel_attributes(ChannelInfo)),
             SpanCtx = otel_tracer:start_span(RootCtx1, ?current_tracer, process_message, #{
                 attributes => Attrs
             }),
@@ -113,22 +113,22 @@ trace_process_publish(Packet, Channel, ProcessFun) ->
             Packet1 = put_ctx_to_packet(Ctx, Packet),
             _ = otel_ctx:attach(Ctx),
             try
-                ProcessFun(Packet1, Channel)
+                ProcessFun(Packet1)
             after
                 _ = ?end_span(),
                 clear()
             end
     end.
 
--spec start_trace_send(list(emqx_types:deliver()), emqx_channel:channel()) ->
+-spec start_trace_send(list(emqx_types:deliver()), emqx_external_trace:channel_info()) ->
     list(emqx_types:deliver()).
-start_trace_send(Delivers, Channel) ->
+start_trace_send(Delivers, ChannelInfo) ->
     lists:map(
         fun({deliver, Topic, Msg} = Deliver) ->
             case get_ctx_from_msg(Msg) of
                 Ctx when is_map(Ctx) ->
                     Attrs = maps:merge(
-                        msg_attributes(Msg), sub_channel_attributes(Channel)
+                        msg_attributes(Msg), sub_channel_attributes(ChannelInfo)
                     ),
                     StartOpts = #{attributes => Attrs},
                     SpanCtx = otel_tracer:start_span(
@@ -216,11 +216,11 @@ msg_attributes(Msg) ->
 packet_attributes(#mqtt_packet{variable = Packet}) ->
     #{'messaging.destination.name' => emqx_packet:info(topic_name, Packet)}.
 
-channel_attributes(Channel) ->
-    #{'messaging.client_id' => emqx_channel:info(clientid, Channel)}.
+channel_attributes(ChannelInfo) ->
+    #{'messaging.client_id' => maps:get(clientid, ChannelInfo, undefined)}.
 
-sub_channel_attributes(Channel) ->
-    channel_attributes(Channel).
+sub_channel_attributes(ChannelInfo) ->
+    channel_attributes(ChannelInfo).
 
 put_ctx_to_msg(OtelCtx, Msg = #message{extra = Extra}) when is_map(Extra) ->
     Msg#message{extra = Extra#{?EMQX_OTEL_CTX => OtelCtx}};