fix(emqx_slow_subs): limit the max size of top-k table

apps/emqx_management/src/emqx_mgmt_api.erl

@@ -30,6 +30,7 @@
 -export([ node_query/5
         , cluster_query/4
         , select_table_with_count/5
+        , b2i/1
         ]).
 
 -export([do_query/6]).

apps/emqx_slow_subs/include/emqx_slow_subs.hrl

@@ -18,6 +18,8 @@
 
 -define(INDEX(Latency, ClientId), {Latency, ClientId}).
 
+-define(MAX_TAB_SIZE, 1000).
+
 -record(top_k, { index :: index()
                , type :: emqx_message_latency_stats:latency_type()
                , last_update_time :: pos_integer()

apps/emqx_slow_subs/src/emqx_slow_subs.erl

@@ -251,7 +251,8 @@ publish(TickTime, Notices) ->
     ok.
 
 load() ->
-    MaxSize = emqx:get_config([emqx_slow_subs, top_k_num]),
+    MaxSizeT = emqx:get_config([emqx_slow_subs, top_k_num]),
+    MaxSize = erlang:min(MaxSizeT, ?MAX_TAB_SIZE),
     _ = emqx:hook('message.slow_subs_stats',
                   {?MODULE, on_stats_update, [#{max_size => MaxSize}]}
                  ),

apps/emqx_slow_subs/src/emqx_slow_subs_api.erl

@@ -87,7 +87,11 @@ slow_subs(delete, _) ->
     ok = emqx_slow_subs:clear_history(),
     {204};
 
-slow_subs(get, #{query_string := QS}) ->
+slow_subs(get, #{query_string := QST}) ->
+    LimitT = maps:get(<<"limit">>, QST, ?MAX_TAB_SIZE),
+    Limit = erlang:min(?MAX_TAB_SIZE, emqx_mgmt_api:b2i(LimitT)),
+    Page = maps:get(<<"page">>, QST, 1),
+    QS = QST#{<<"limit">> => Limit, <<"page">> => Page},
     Data = emqx_mgmt_api:paginate({?TOPK_TAB, [{traverse, last_prev}]}, QS, ?FORMAT_FUN),
     {200, Data}.
 

apps/emqx_slow_subs/src/emqx_slow_subs_schema.erl

@@ -14,7 +14,7 @@ fields("emqx_slow_subs") ->
           "The latency threshold for statistics, the minimum value is 100ms")}
     , {expire_interval,
        sc(emqx_schema:duration_ms(),
-          "5m",
+          "300s",
           "The eviction time of the record, which in the statistics record table")}
     , {top_k_num,
        sc(integer(),

apps/emqx_slow_subs/test/emqx_slow_subs_SUITE.erl

@@ -90,7 +90,7 @@ t_log_and_pub(_) ->
     ?assert(RecSum >= 5),
     ?assert(lists:all(fun(E) -> E =< 3 end, Recs)),
 
-    timer:sleep(2000),
+    timer:sleep(3000),
     ?assert(ets:info(?TOPK_TAB, size) =:= 0),
     [Client ! stop || Client <- Clients],
     ok.