fix(retain): add `hasnext` into the meta data for the `GET /retain/messages`

apps/emqx_retainer/src/emqx_retainer.erl

@@ -78,7 +78,7 @@
 -callback store_retained(context(), message()) -> ok.
 -callback read_message(context(), topic()) -> {ok, list()}.
 -callback page_read(context(), topic(), non_neg_integer(), non_neg_integer()) ->
-    {ok, list()}.
+    {ok, HasNext :: boolean(), list()}.
 -callback match_messages(context(), topic(), cursor()) -> {ok, list(), cursor()}.
 -callback clear_expired(context()) -> ok.
 -callback clean(context()) -> ok.

apps/emqx_retainer/src/emqx_retainer_api.erl

@@ -181,15 +181,27 @@ lookup_retained(get, #{query_string := Qs}) ->
     Page = maps:get(<<"page">>, Qs, 1),
     Limit = maps:get(<<"limit">>, Qs, emqx_mgmt:default_row_limit()),
     Topic = maps:get(<<"topic">>, Qs, undefined),
-    {ok, Msgs} = emqx_retainer_mnesia:page_read(undefined, Topic, Page, Limit),
+    {ok, HasNext, Msgs} = emqx_retainer_mnesia:page_read(undefined, Topic, Page, Limit),
+    Meta =
+        case Topic of
+            undefined ->
+                #{count => emqx_retainer_mnesia:size(?TAB_MESSAGE)};
+            _ ->
+                #{}
+        end,
     {200, #{
         data => [format_message(Msg) || Msg <- Msgs],
-        meta => #{page => Page, limit => Limit, count => emqx_retainer_mnesia:size(?TAB_MESSAGE)}
+        meta =>
+            Meta#{
+                page => Page,
+                limit => Limit,
+                hasnext => HasNext
+            }
     }}.
 
 with_topic(get, #{bindings := Bindings}) ->
     Topic = maps:get(topic, Bindings),
-    {ok, Msgs} = emqx_retainer_mnesia:page_read(undefined, Topic, 1, 1),
+    {ok, _, Msgs} = emqx_retainer_mnesia:page_read(undefined, Topic, 1, 1),
     case Msgs of
         [H | _] ->
             {200, format_detail_message(H)};
@@ -202,12 +214,12 @@ with_topic(get, #{bindings := Bindings}) ->
 with_topic(delete, #{bindings := Bindings}) ->
     Topic = maps:get(topic, Bindings),
     case emqx_retainer_mnesia:page_read(undefined, Topic, 1, 1) of
-        {ok, []} ->
+        {ok, _, []} ->
             {404, #{
                 code => <<"NOT_FOUND">>,
                 message => <<"Viewed message doesn't exist">>
             }};
-        {ok, _} ->
+        {ok, _, _} ->
             emqx_retainer_mnesia:delete_message(undefined, Topic),
             {204}
     end.

apps/emqx_retainer/src/emqx_retainer_mnesia.erl

@@ -231,20 +231,18 @@ page_read(_, Topic, Page, Limit) ->
             false ->
                 more
         end,
-    PageRows =
     case SkipResult of
         closed ->
-                [];
+            {ok, false, []};
         more ->
             case qlc_next_answers(Cursor, Limit) of
                 {closed, Rows} ->
-                        Rows;
+                    {ok, false, Rows};
                 {more, Rows} ->
                     qlc:delete_cursor(Cursor),
-                        Rows
+                    {ok, true, Rows}
             end
-        end,
+    end.
-    {ok, PageRows}.
 
 clean(_) ->
     _ = mria:clear_table(?TAB_MESSAGE),

apps/emqx_retainer/test/emqx_retainer_SUITE.erl

@@ -133,7 +133,7 @@ t_store_and_clean(_) ->
     ),
     timer:sleep(100),
 
-    {ok, List} = emqx_retainer:page_read(<<"retained">>, 1, 10),
+    {ok, _, List} = emqx_retainer:page_read(<<"retained">>, 1, 10),
     ?assertEqual(1, length(List)),
     ?assertMatch(
         {ok, [#message{payload = <<"this is a retained message">>}]},
@@ -159,7 +159,7 @@ t_store_and_clean(_) ->
     ),
 
     ok = emqx_retainer:clean(),
-    {ok, List2} = emqx_retainer:page_read(<<"retained">>, 1, 10),
+    {ok, _, List2} = emqx_retainer:page_read(<<"retained">>, 1, 10),
     ?assertEqual(0, length(List2)),
     ?assertMatch(
         {ok, []},
@@ -486,12 +486,12 @@ t_clear_expired(_) ->
         ),
         timer:sleep(1000),
 
-        {ok, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
+        {ok, _, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
         ?assertEqual(5, erlang:length(List)),
 
         timer:sleep(4500),
 
-        {ok, List2} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
+        {ok, _, List2} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
         ?assertEqual(0, erlang:length(List2)),
 
         ok = emqtt:disconnect(C1)
@@ -522,7 +522,7 @@ t_max_payload_size(_) ->
         ),
 
         timer:sleep(500),
-        {ok, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
+        {ok, _, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 10),
         ?assertEqual(1, erlang:length(List)),
 
         ok = emqtt:disconnect(C1)
@@ -546,10 +546,10 @@ t_page_read(_) ->
     lists:foreach(Fun, lists:seq(1, 9)),
     timer:sleep(200),
 
-    {ok, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 5),
+    {ok, _, List} = emqx_retainer:page_read(<<"retained/+">>, 1, 5),
     ?assertEqual(5, length(List)),
 
-    {ok, List2} = emqx_retainer:page_read(<<"retained/+">>, 2, 5),
+    {ok, _, List2} = emqx_retainer:page_read(<<"retained/+">>, 2, 5),
     ?assertEqual(4, length(List2)),
 
     ok = emqtt:disconnect(C1).