fix(mgmt clients api): hold channel info after client disconnects for display in api

Fixes https://emqx.atlassian.net/browse/EMQX-12266

apps/emqx/src/emqx_persistent_session_ds.erl

@@ -658,16 +658,17 @@ replay_batch(Srs0, Session0, ClientInfo) ->
 %%--------------------------------------------------------------------
 
 -spec disconnect(session(), emqx_types:conninfo()) -> {shutdown, session()}.
-disconnect(Session = #{s := S0}, ConnInfo) ->
-    S1 = emqx_persistent_session_ds_state:set_last_alive_at(now_ms(), S0),
-    S2 =
+disconnect(Session = #{id := Id, s := S0}, ConnInfo) ->
+    S1 = maybe_set_offline_info(S0, Id),
+    S2 = emqx_persistent_session_ds_state:set_last_alive_at(now_ms(), S1),
+    S3 =
         case ConnInfo of
             #{expiry_interval := EI} when is_number(EI) ->
-                emqx_persistent_session_ds_state:set_expiry_interval(EI, S1);
+                emqx_persistent_session_ds_state:set_expiry_interval(EI, S2);
             _ ->
-                S1
+                S2
         end,
-    S = emqx_persistent_session_ds_state:commit(S2),
+    S = emqx_persistent_session_ds_state:commit(S3),
     {shutdown, Session#{s => S}}.
 
 -spec terminate(Reason :: term(), session()) -> ok.
@@ -1175,6 +1176,19 @@ try_get_live_session(ClientId) ->
             not_found
     end.
 
+-spec maybe_set_offline_info(emqx_persistent_session_ds_state:t(), emqx_types:clientid()) ->
+    emqx_persistent_session_ds_state:t().
+maybe_set_offline_info(S, Id) ->
+    case emqx_cm:lookup_client({clientid, Id}) of
+        [{_Key, ChannelInfo, Stats}] ->
+            emqx_persistent_session_ds_state:set_offline_info(
+                #{chan_info => ChannelInfo, stats => Stats},
+                S
+            );
+        _ ->
+            S
+    end.
+
 %%--------------------------------------------------------------------
 %% SeqNo tracking
 %% --------------------------------------------------------------------

apps/emqx/src/emqx_persistent_session_ds.hrl

@@ -81,5 +81,6 @@
 -define(will_message, will_message).
 -define(clientinfo, clientinfo).
 -define(protocol, protocol).
+-define(offline_info, offline_info).
 
 -endif.

apps/emqx/src/emqx_persistent_session_ds_state.erl

@@ -35,6 +35,7 @@
 -export([get_expiry_interval/1, set_expiry_interval/2]).
 -export([get_clientinfo/1, set_clientinfo/2]).
 -export([get_will_message/1, set_will_message/2, clear_will_message/1, clear_will_message_now/1]).
+-export([set_offline_info/2]).
 -export([get_peername/1, set_peername/2]).
 -export([get_protocol/1, set_protocol/2]).
 -export([new_id/1]).
@@ -372,6 +373,10 @@ clear_will_message_now(SessionId) when is_binary(SessionId) ->
 clear_will_message(Rec) ->
     set_will_message(undefined, Rec).
 
+-spec set_offline_info(_Info :: map(), t()) -> t().
+set_offline_info(Info, Rec) ->
+    set_meta(?offline_info, Info, Rec).
+
 -spec new_id(t()) -> {emqx_persistent_session_ds:subscription_id(), t()}.
 new_id(Rec) ->
     LastId =

apps/emqx_management/src/emqx_mgmt_api_clients.erl

@@ -1745,6 +1745,17 @@ format_channel_info(WhichNode, {_, ClientInfo0, ClientStats}, Opts) ->
 format_channel_info(undefined, {ClientId, PSInfo0 = #{}}, _Opts) ->
     format_persistent_session_info(ClientId, PSInfo0).
 
+format_persistent_session_info(
+    _ClientId, #{metadata := #{offline_info := #{chan_info := ChanInfo, stats := Stats}}} = PSInfo
+) ->
+    Info0 = format_channel_info(_Node = undefined, {_Key = undefined, ChanInfo, Stats}, #{
+        fields => all
+    }),
+    Info0#{
+        connected => false,
+        is_persistent => true,
+        subscriptions_cnt => maps:size(maps:get(subscriptions, PSInfo, #{}))
+    };
 format_persistent_session_info(ClientId, PSInfo0) ->
     Metadata = maps:get(metadata, PSInfo0, #{}),
     {ProtoName, ProtoVer} = maps:get(protocol, Metadata),

apps/emqx_management/test/emqx_mgmt_api_clients_SUITE.erl

@@ -1800,6 +1800,11 @@ maybe_json_decode(X) ->
         {error, _} -> X
     end.
 
+get_client_request(Port, ClientId) ->
+    Host = "http://127.0.0.1:" ++ integer_to_list(Port),
+    Path = emqx_mgmt_api_test_util:api_path(Host, ["clients", ClientId]),
+    request(get, Path, []).
+
 list_request(Port) ->
     list_request(Port, _QueryParams = "").
 
@@ -1874,6 +1879,19 @@ assert_single_client(Opts) ->
         {ok, {{_, 200, _}, _, #{<<"connected">> := IsConnected}}},
         lookup_request(ClientId, APIPort)
     ),
+    ?assertMatch(
+        {ok,
+            {{_, 200, _}, _, #{
+                <<"connected">> := IsConnected,
+                <<"is_persistent">> := true,
+                %% contains statistics from disconnect time
+                <<"recv_pkt">> := _,
+                %% contains channel info from disconnect time
+                <<"listener">> := _,
+                <<"clean_start">> := _
+            }}},
+        get_client_request(APIPort, ClientId)
+    ),
     ok.
 
 connect_client(Opts) ->