Add runtime callback for 'pingreq' messages (#24)

* Add runtime callback for 'pingreq' messages

* CI: remove OTP 24, add OTP 27

Author: mworrell

.github/workflows/test.yml

@@ -18,7 +18,7 @@ jobs:
 
     strategy:
       matrix:
-        otp_version: [24, 25, 26]
+        otp_version: [25, 26, 27]
         os: [ubuntu-latest]
 
     container:

src/mqtt_sessions_process.erl

@@ -416,8 +416,10 @@ handle_incoming(#{ type := subscribe } = Msg, _Options, State) ->
 handle_incoming(#{ type := unsubscribe } = Msg, _Options, State) ->
     packet_unsubscribe(Msg, State);
 
-handle_incoming(#{ type := pingreq }, _Options, State) ->
-    State1 = reply_or_drop(#{ type => pingresp }, State),
+handle_incoming(#{ type := pingreq } = Msg, _Options, State) ->
+    #state{ runtime = Runtime, user_context = UserContext } = State,
+    {ok, UserContext1} = Runtime:ping(UserContext),
+    State1 = reply_or_drop(#{ type => pingresp }, State#state{ user_context = UserContext1 }),
     {ok, State1};
 handle_incoming(#{ type := pingresp }, _Options, State) ->
     {ok, State};

src/mqtt_sessions_runtime.erl

@@ -25,6 +25,7 @@
     new_user_context/3,
     connect/4,
     control_message/3,
+    ping/1,
     reauth/2,
     is_allowed/4,
     is_valid_message/3
@@ -152,6 +153,12 @@ connect(_Packet, _IsSessionPresent, _Options, UserContext) ->
 reauth(#{ type := auth }, _UserContext) ->
     {error, notsupported}.
 
+%% @doc Called on a pingreq message from the remote. Used this to keep processes or track connection status.
+-spec ping(UserContext) -> {ok, UserContext1} when
+    UserContext :: user_context(),
+    UserContext1 :: user_context().
+ping(UserContext) ->
+    {ok, UserContext}.
 
 -spec is_allowed( publish | subscribe, topic(), mqtt_packet_map:mqtt_packet(), user_context()) -> boolean().
 is_allowed(publish, _Topic, _Packet, _UserContext) ->