fix(sessmem): avoid defining unsafe defaults in `#session`

apps/emqx/include/emqx_session_mem.hrl

@@ -26,7 +26,7 @@
     %% Client’s Subscriptions.
     subscriptions :: map(),
     %% Max subscriptions allowed
-    max_subscriptions = infinity :: non_neg_integer() | infinity,
+    max_subscriptions :: non_neg_integer() | infinity,
     %% Upgrade QoS?
     upgrade_qos = false :: boolean(),
     %% Client <- Broker: QoS1/2 messages sent to the client but
@@ -40,14 +40,14 @@
     %% Next packet id of the session
     next_pkt_id = 1 :: emqx_types:packet_id(),
     %% Retry interval for redelivering QoS1/2 messages (Unit: millisecond)
-    retry_interval = 0 :: timeout(),
+    retry_interval :: timeout(),
     %% Client -> Broker: QoS2 messages received from the client, but
     %% have not been completely acknowledged
     awaiting_rel :: map(),
     %% Maximum number of awaiting QoS2 messages allowed
-    max_awaiting_rel = infinity :: non_neg_integer() | infinity,
+    max_awaiting_rel :: non_neg_integer() | infinity,
     %% Awaiting PUBREL Timeout (Unit: millisecond)
-    await_rel_timeout = 0 :: timeout(),
+    await_rel_timeout :: timeout(),
     %% Created at
     created_at :: pos_integer()
 }).

apps/emqx/src/emqx_session_mem.erl

@@ -158,7 +158,7 @@ create(
     Conf
 ) ->
     QueueOpts = get_mqueue_conf(Zone),
-    Session = #session{
+    #session{
         id = emqx_guid:gen(),
         clientid = ClientId,
         created_at = erlang:system_time(millisecond),
@@ -167,9 +167,13 @@ create(
         inflight = emqx_inflight:new(ReceiveMax),
         mqueue = emqx_mqueue:init(QueueOpts),
         next_pkt_id = 1,
-        awaiting_rel = #{}
-    },
-    preserve_conf(Conf, Session).
+        awaiting_rel = #{},
+        max_subscriptions = maps:get(max_subscriptions, Conf),
+        max_awaiting_rel = maps:get(max_awaiting_rel, Conf),
+        upgrade_qos = maps:get(upgrade_qos, Conf),
+        retry_interval = maps:get(retry_interval, Conf),
+        await_rel_timeout = maps:get(await_rel_timeout, Conf)
+    }.
 
 get_mqueue_conf(Zone) ->
     #{
@@ -204,7 +208,7 @@ open(ClientInfo = #{clientid := ClientId}, ConnInfo, Conf) ->
             case emqx_cm:takeover_session_end(TakeoverState) of
                 {ok, Pendings} ->
                     Session1 = resize_inflight(ConnInfo, Session0),
-                    Session = preserve_conf(Conf, Session1),
+                    Session = apply_conf(Conf, Session1),
                     clean_session(ClientInfo, Session, Pendings);
                 {error, _} ->
                     % TODO log error?
@@ -219,7 +223,7 @@ resize_inflight(#{receive_maximum := ReceiveMax}, Session = #session{inflight =
         inflight = emqx_inflight:resize(ReceiveMax, Inflight)
     }.
 
-preserve_conf(Conf, Session = #session{}) ->
+apply_conf(Conf, Session = #session{}) ->
     Session#session{
         max_subscriptions = maps:get(max_subscriptions, Conf),
         max_awaiting_rel = maps:get(max_awaiting_rel, Conf),