feat: add mqtt runtime insights to telemetry data

apps/emqx_modules/src/emqx_telemetry.erl

@@ -76,10 +76,13 @@
 -record(state, {
     uuid :: undefined | binary(),
     url :: string(),
-    report_interval :: undefined | non_neg_integer(),
+    report_interval :: non_neg_integer(),
-    timer = undefined :: undefined | reference()
+    timer = undefined :: undefined | reference(),
+    previous_metrics = #{} :: map()
 }).
 
+-type state() :: #state{}.
+
 %% The count of 100-nanosecond intervals between the UUID epoch
 %% 1582-10-15 00:00:00 and the UNIX epoch 1970-01-01 00:00:00.
 -define(GREGORIAN_EPOCH_OFFSET, 16#01b21dd213814000).
@@ -136,6 +139,7 @@ get_telemetry() ->
 %% is very small, it should be safe to ignore.
 -dialyzer([{nowarn_function, [init/1]}]).
 init(_Opts) ->
+    State0 = empty_state(),
     UUID1 =
         case mnesia:dirty_read(?TELEMETRY, ?UNIQUE_ID) of
             [] ->
@@ -148,19 +152,15 @@ init(_Opts) ->
             [#telemetry{uuid = UUID} | _] ->
                 UUID
         end,
-    {ok, #state{
+    {ok, State0#state{uuid = UUID1}}.
-        url = ?TELEMETRY_URL,
-        report_interval = timer:seconds(?REPORT_INTERVAL),
-        uuid = UUID1
-    }}.
 
-handle_call(enable, _From, State) ->
+handle_call(enable, _From, State0) ->
     case ?MODULE:official_version(emqx_app:get_release()) of
         true ->
-            report_telemetry(State),
+            State = report_telemetry(State0),
             {reply, ok, ensure_report_timer(State)};
         false ->
-            {reply, {error, not_official_version}, State}
+            {reply, {error, not_official_version}, State0}
     end;
 handle_call(disable, _From, State = #state{timer = Timer}) ->
     case ?MODULE:official_version(emqx_app:get_release()) of
@@ -173,7 +173,8 @@ handle_call(disable, _From, State = #state{timer = Timer}) ->
 handle_call(get_uuid, _From, State = #state{uuid = UUID}) ->
     {reply, {ok, UUID}, State};
 handle_call(get_telemetry, _From, State) ->
-    {reply, {ok, get_telemetry(State)}, State};
+    {_State, Telemetry} = get_telemetry(State),
+    {reply, {ok, Telemetry}, State};
 handle_call(Req, _From, State) ->
     ?SLOG(error, #{msg => "unexpected_call", call => Req}),
     {reply, ignored, State}.
@@ -186,10 +187,11 @@ handle_continue(Continue, State) ->
     ?SLOG(error, #{msg => "unexpected_continue", continue => Continue}),
     {noreply, State}.
 
-handle_info({timeout, TRef, time_to_report_telemetry_data}, State = #state{timer = TRef}) ->
+handle_info({timeout, TRef, time_to_report_telemetry_data}, State0 = #state{timer = TRef}) ->
+    State =
         case get_status() of
-        true -> report_telemetry(State);
+            true -> report_telemetry(State0);
-        false -> ok
+            false -> State0
         end,
     {noreply, ensure_report_timer(State)};
 handle_info(Info, State) ->
@@ -307,6 +309,9 @@ messages_sent() ->
 messages_received() ->
     emqx_metrics:val('messages.received').
 
+topic_count() ->
+    emqx_stats:getstat('topics.count').
+
 generate_uuid() ->
     MicroSeconds = erlang:system_time(microsecond),
     Timestamp = MicroSeconds * 10 + ?GREGORIAN_EPOCH_OFFSET,
@@ -323,9 +328,11 @@ generate_uuid() ->
         )
     ).
 
-get_telemetry(#state{uuid = UUID}) ->
+-spec get_telemetry(state()) -> {state(), proplists:proplist()}.
+get_telemetry(State0 = #state{uuid = UUID}) ->
     OSInfo = os_info(),
-    [
+    {MQTTRTInsights, State} = mqtt_runtime_insights(State0),
+    {State, [
         {emqx_version, bin(emqx_app:get_release())},
         {license, [{edition, <<"community">>}]},
         {os_name, bin(get_value(os_name, OSInfo))},
@@ -339,11 +346,12 @@ get_telemetry(#state{uuid = UUID}) ->
         {messages_received, messages_received()},
         {messages_sent, messages_sent()},
         {build_info, build_info()},
-        {vm_specs, vm_specs()}
+        {vm_specs, vm_specs()},
-    ].
+        {mqtt_runtime_insights, MQTTRTInsights}
+    ]}.
 
-report_telemetry(State = #state{url = URL}) ->
+report_telemetry(State0 = #state{url = URL}) ->
-    Data = get_telemetry(State),
+    {State, Data} = get_telemetry(State0),
     case emqx_json:safe_encode(Data) of
         {ok, Bin} ->
             httpc_request(post, URL, [], Bin),
@@ -351,7 +359,8 @@ report_telemetry(State = #state{url = URL}) ->
         {error, Reason} ->
             %% debug? why?
             ?tp(debug, telemetry_data_encode_error, #{data => Data, reason => Reason})
-    end.
+    end,
+    State.
 
 httpc_request(Method, URL, Headers, Body) ->
     HTTPOptions = [{timeout, 10_000}],
@@ -401,9 +410,52 @@ vm_specs() ->
         {total_memory, proplists:get_value(available_memory, SysMemData)}
     ].
 
+-spec mqtt_runtime_insights(state()) -> {map(), state()}.
+mqtt_runtime_insights(State0) ->
+    {MQTTRates, State} = update_mqtt_rates(State0),
+    MQTTRTInsights = MQTTRates#{num_topics => topic_count()},
+    {MQTTRTInsights, State}.
+
+-spec update_mqtt_rates(state()) -> {map(), state()}.
+update_mqtt_rates(
+    State = #state{
+        previous_metrics = PrevMetrics0,
+        report_interval = ReportInterval
+    }
+) when
+    is_integer(ReportInterval), ReportInterval > 0
+->
+    MetricsToCheck =
+        [
+            {messages_sent_rate, messages_sent, fun messages_sent/0},
+            {messages_received_rate, messages_received, fun messages_received/0}
+        ],
+    {Metrics, PrevMetrics} =
+        lists:foldl(
+            fun({RateKey, CountKey, Fun}, {Rates0, PrevMetrics1}) ->
+                NewCount = Fun(),
+                OldCount = maps:get(CountKey, PrevMetrics1, 0),
+                Rate = (NewCount - OldCount) / ReportInterval,
+                Rates = Rates0#{RateKey => Rate},
+                PrevMetrics2 = PrevMetrics1#{CountKey => NewCount},
+                {Rates, PrevMetrics2}
+            end,
+            {#{}, PrevMetrics0},
+            MetricsToCheck
+        ),
+    {Metrics, State#state{previous_metrics = PrevMetrics}};
+update_mqtt_rates(State) ->
+    {#{}, State}.
+
 bin(L) when is_list(L) ->
     list_to_binary(L);
 bin(A) when is_atom(A) ->
     atom_to_binary(A);
 bin(B) when is_binary(B) ->
     B.
+
+empty_state() ->
+    #state{
+        url = ?TELEMETRY_URL,
+        report_interval = timer:seconds(?REPORT_INTERVAL)
+    }.

apps/emqx_modules/test/emqx_telemetry_SUITE.erl

@@ -134,6 +134,10 @@ t_get_telemetry(_Config) ->
     ?assert(0 =< get_value(num_cpus, VMSpecs)),
     ?assert(is_integer(get_value(total_memory, VMSpecs))),
     ?assert(0 =< get_value(total_memory, VMSpecs)),
+    MQTTRTInsights = get_value(mqtt_runtime_insights, TelemetryData),
+    ?assert(is_number(maps:get(messages_sent_rate, MQTTRTInsights))),
+    ?assert(is_number(maps:get(messages_received_rate, MQTTRTInsights))),
+    ?assert(is_integer(maps:get(num_topics, MQTTRTInsights))),
     ok.
 
 t_enable(_) ->
@@ -156,6 +160,31 @@ t_send_after_enable(_) ->
         meck:unload([emqx_telemetry])
     end.
 
+t_mqtt_runtime_insights(_) ->
+    State0 = emqx_telemetry:empty_state(),
+    {MQTTRTInsights1, State1} = emqx_telemetry:mqtt_runtime_insights(State0),
+    ?assertEqual(
+        #{
+            messages_sent_rate => 0.0,
+            messages_received_rate => 0.0,
+            num_topics => 0
+        },
+        MQTTRTInsights1
+    ),
+    %% add some fake stats
+    emqx_metrics:set('messages.sent', 10_000_000_000),
+    emqx_metrics:set('messages.received', 20_000_000_000),
+    emqx_stats:setstat('topics.count', 30_000),
+    {MQTTRTInsights2, _State2} = emqx_telemetry:mqtt_runtime_insights(State1),
+    assert_approximate(MQTTRTInsights2, messages_sent_rate, "16.53"),
+    assert_approximate(MQTTRTInsights2, messages_received_rate, "33.07"),
+    ?assertEqual(30_000, maps:get(num_topics, MQTTRTInsights2)),
+    ok.
+
+assert_approximate(Map, Key, Expected) ->
+    Value = maps:get(Key, Map),
+    ?assertEqual(Expected, float_to_list(Value, [{decimals, 2}])).
+
 bin(L) when is_list(L) ->
     list_to_binary(L);
 bin(B) when is_binary(B) ->