From 068421d0e14d50ef35c9f7fe3eb92311586a7513 Mon Sep 17 00:00:00 2001
From: Zhongwen Deng <zhongwencool@gmail.com>
Date: Sat, 7 May 2022 16:48:03 +0800
Subject: [PATCH] feat: don't dispatch requests until dispatch is ready

---
 apps/emqx/src/emqx_tls_lib.erl                | 28 ++++++++-----------
 apps/emqx_dashboard/src/emqx_dashboard.erl    |  2 +-
 .../src/emqx_dashboard_listener.erl           | 17 +++++++----
 .../src/emqx_dashboard_middleware.erl         | 20 +++++++++++++
 4 files changed, 44 insertions(+), 23 deletions(-)

diff --git a/apps/emqx/src/emqx_tls_lib.erl b/apps/emqx/src/emqx_tls_lib.erl
index 17aaad74e..f59a67f4a 100644
--- a/apps/emqx/src/emqx_tls_lib.erl
+++ b/apps/emqx/src/emqx_tls_lib.erl
@@ -27,9 +27,6 @@
     all_ciphers/0
 ]).
 
--compile(export_all).
--compile(nowarn_export_all).
-
 %% SSL files
 -export([
     ensure_ssl_files/2,
@@ -219,19 +216,18 @@ default_versions(_) ->
 %% Deduplicate a list without re-ordering the elements.
 dedup([]) ->
     [];
-dedup(List) ->
-    lists:reverse(
-        lists:foldl(
-            fun(L, Acc) ->
-                case lists:member(L, Acc) of
-                    false -> [L | Acc];
-                    true -> Acc
-                end
-            end,
-            [],
-            List
-        )
-    ).
+dedup(List0) ->
+    List = lists:foldl(
+        fun(L, Acc) ->
+            case lists:member(L, Acc) of
+                false -> [L | Acc];
+                true -> Acc
+            end
+        end,
+        [],
+        List0
+    ),
+    lists:reverse(List).
 
 %% parse comma separated tls version strings
 parse_versions(Versions) ->
diff --git a/apps/emqx_dashboard/src/emqx_dashboard.erl b/apps/emqx_dashboard/src/emqx_dashboard.erl
index 6c50ca0c7..974d438be 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard.erl
@@ -81,7 +81,7 @@ start_listeners(Listeners) ->
         security => [#{'basicAuth' => []}, #{'bearerAuth' => []}],
         swagger_global_spec => GlobalSpec,
         dispatch => Dispatch,
-        middlewares => [cowboy_router, ?EMQX_MIDDLE, cowboy_handler]
+        middlewares => [?EMQX_MIDDLE, cowboy_router, cowboy_handler]
     },
     Res =
         lists:foldl(
diff --git a/apps/emqx_dashboard/src/emqx_dashboard_listener.erl b/apps/emqx_dashboard/src/emqx_dashboard_listener.erl
index db06d42ab..31f309f9a 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard_listener.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard_listener.erl
@@ -25,7 +25,7 @@
 
 -behaviour(gen_server).
 
--export([start_link/0]).
+-export([start_link/0, is_ready/0]).
 
 -export([
     init/1,
@@ -37,29 +37,34 @@
     code_change/3
 ]).
 
+is_ready() ->
+    ready =:= gen_server:call(?MODULE, get_state, 10000).
+
 start_link() ->
     gen_server:start_link({local, ?MODULE}, ?MODULE, [], []).
 
 init([]) ->
     erlang:process_flag(trap_exit, true),
     ok = add_handler(),
-    {ok, #{}, {continue, regenerate_dispatch}}.
+    {ok, undefined, {continue, regenerate_dispatch}}.
 
-handle_continue(regenerate_dispatch, State) ->
+handle_continue(regenerate_dispatch, _State) ->
     regenerate_minirest_dispatch(),
-    {noreply, State, hibernate}.
+    {noreply, ready, hibernate}.
 
+handle_call(get_state, _From, State) ->
+    {reply, State, State, hibernate};
 handle_call(_Request, _From, State) ->
     {reply, ok, State, hibernate}.
 
 handle_cast(_Request, State) ->
     {noreply, State, hibernate}.
 
-handle_info({update_listeners, OldListeners, NewListeners}, State) ->
+handle_info({update_listeners, OldListeners, NewListeners}, _State) ->
     ok = emqx_dashboard:stop_listeners(OldListeners),
     ok = emqx_dashboard:start_listeners(NewListeners),
     regenerate_minirest_dispatch(),
-    {noreply, State, hibernate};
+    {noreply, ready, hibernate};
 handle_info(_Info, State) ->
     {noreply, State, hibernate}.
 
diff --git a/apps/emqx_dashboard/src/emqx_dashboard_middleware.erl b/apps/emqx_dashboard/src/emqx_dashboard_middleware.erl
index 77b6dbdd0..b07ab21f4 100644
--- a/apps/emqx_dashboard/src/emqx_dashboard_middleware.erl
+++ b/apps/emqx_dashboard/src/emqx_dashboard_middleware.erl
@@ -21,6 +21,7 @@
 -export([execute/2]).
 
 execute(Req, Env) ->
+    waiting_dispatch_ready(),
     CORS = emqx_conf:get([dashboard, cors], false),
     case CORS andalso cowboy_req:header(<<"origin">>, Req, undefined) of
         false ->
@@ -31,3 +32,22 @@ execute(Req, Env) ->
             Req2 = cowboy_req:set_resp_header(<<"Access-Control-Allow-Origin">>, <<"*">>, Req),
             {ok, Req2, Env}
     end.
+
+waiting_dispatch_ready() ->
+    waiting_dispatch_ready(5).
+
+waiting_dispatch_ready(0) ->
+    ok;
+waiting_dispatch_ready(Count) ->
+    case emqx_sys:uptime() < timer:minutes(1) of
+        true ->
+            case emqx_dashboard_listener:is_ready() of
+                true ->
+                    ok;
+                false ->
+                    timer:sleep(100),
+                    waiting_dispatch_ready(Count - 1)
+            end;
+        false ->
+            ok
+    end.