fix(persistent_sessions): channels can terminate without a session

apps/emqx/src/emqx_channel.erl

@@ -1179,20 +1179,27 @@ terminate(_, #channel{conn_state = idle}) -> ok;
 terminate(normal, Channel) ->
     run_terminate_hook(normal, Channel);
 terminate({shutdown, kicked}, Channel) ->
-    _ = emqx_persistent_session:persist(Channel#channel.clientinfo,
-                                        Channel#channel.conninfo,
-                                        Channel#channel.session),
+    persist_if_session(Channel),
     run_terminate_hook(kicked, Channel);
 terminate({shutdown, Reason}, Channel) when Reason =:= discarded;
                                             Reason =:= takeovered ->
     run_terminate_hook(Reason, Channel);
 terminate(Reason, Channel = #channel{will_msg = WillMsg}) ->
     (WillMsg =/= undefined) andalso publish_will_msg(WillMsg),
-    _ = emqx_persistent_session:persist(Channel#channel.clientinfo,
-                                        Channel#channel.conninfo,
-                                        Channel#channel.session),
+    persist_if_session(Channel),
     run_terminate_hook(Reason, Channel).
 
+persist_if_session(#channel{session = Session} = Channel) ->
+    case emqx_session:is_session(Session) of
+        true ->
+            _ = emqx_persistent_session:persist(Channel#channel.clientinfo,
+                                                Channel#channel.conninfo,
+                                                Channel#channel.session),
+            ok;
+        false ->
+            ok
+    end.
+
 run_terminate_hook(_Reason, #channel{session = undefined}) -> ok;
 run_terminate_hook(Reason, #channel{clientinfo = ClientInfo, session = Session}) ->
     emqx_session:terminate(ClientInfo, Reason, Session).

apps/emqx/src/emqx_session.erl

@@ -58,6 +58,7 @@
 
 -export([ info/1
         , info/2
+        , is_session/1
         , stats/1
         ]).
 
@@ -202,6 +203,9 @@ init(Opts) ->
 %% Info, Stats
 %%--------------------------------------------------------------------
 
+is_session(#session{}) -> true;
+is_session(_) -> false.
+
 %% @doc Get infos of the session.
 -spec(info(session()) -> emqx_types:infos()).
 info(Session) ->