feat(exhook): make request_failed_action working

apps/emqx_exhook/etc/emqx_exhook.conf

@@ -0,0 +1,38 @@
+##====================================================================
+## EMQ X Hooks
+##====================================================================
+
+exhook: {
+    ## The default value or action will be returned, while the request to
+    ## the gRPC server failed or no available grpc server running.
+    ##
+    ## Default: deny
+    ## Value: ignore | deny
+    request_failed_action: deny
+
+    ## The timeout to request grpc server
+    ##
+    ## Default: 5s
+    ## Value: Duration
+    request_timeout: 5s
+
+    ## Whether to automatically reconnect (initialize) the gRPC server
+    ##
+    ## When gRPC is not available, exhook tries to request the gRPC service at
+    ## that interval and reinitialize the list of mounted hooks.
+    ##
+    ## Default: false
+    ## Value: false | Duration
+    auto_reconnect: 60s
+
+    servers: [
+    #    { name: "default"
+    #      url: "http://127.0.0.1:9000"
+    #      #ssl: {
+    #      #  cacertfile: "{{ platform_etc_dir }}/certs/cacert.pem"
+    #      #  certfile: "{{ platform_etc_dir }}/certs/cert.pem"
+    #      #  keyfile: "{{ platform_etc_dir }}/certs/key.pem"
+    #      #}
+    #    }
+    ]
+}

apps/emqx_exhook/src/emqx_exhook.erl

@@ -64,29 +64,54 @@ cast(Hookpoint, Req) ->
 
 cast(_, _, []) ->
     ok;
-cast(Hookpoint, Req, [ServiceName|More]) ->
+cast(Hookpoint, Req, [ServerName|More]) ->
     %% XXX: Need a real asynchronous running
     _ = emqx_exhook_server:call(Hookpoint, Req,
-                                emqx_exhook_mngr:server(ServiceName)),
+                                emqx_exhook_mngr:server(ServerName)),
     cast(Hookpoint, Req, More).
 
 -spec call_fold(atom(), term(), function())
   -> {ok, term()}
    | {stop, term()}.
 call_fold(Hookpoint, Req, AccFun) ->
-    call_fold(Hookpoint, Req, AccFun, emqx_exhook_mngr:running()).
+    FailedAction = emqx_exhook_mngr:get_request_failed_action(),
+    ServerNames = emqx_exhook_mngr:running(),
+    case ServerNames == [] andalso FailedAction == deny of
+        true ->
+            {stop, deny_action_result(Hookpoint, Req)};
+        _ ->
+            call_fold(Hookpoint, Req, FailedAction, AccFun, ServerNames)
+    end.
 
-call_fold(_, Req, _, []) ->
+call_fold(_, Req, _, _, []) ->
     {ok, Req};
-call_fold(Hookpoint, Req, AccFun, [ServiceName|More]) ->
-    case emqx_exhook_server:call(Hookpoint, Req,
-                                 emqx_exhook_mngr:server(ServiceName)) of
+call_fold(Hookpoint, Req, FailedAction, AccFun, [ServerName|More]) ->
+    Server = emqx_exhook_mngr:server(ServerName),
+    case emqx_exhook_server:call(Hookpoint, Req, Server) of
         {ok, Resp} ->
             case AccFun(Req, Resp) of
-                {stop, NReq} -> {stop, NReq};
-                {ok, NReq} -> call_fold(Hookpoint, NReq, AccFun, More);
-                _ -> call_fold(Hookpoint, Req, AccFun, More)
+                {stop, NReq} ->
+                    {stop, NReq};
+                {ok, NReq} ->
+                    call_fold(Hookpoint, NReq, FailedAction, AccFun, More);
+                _ ->
+                    call_fold(Hookpoint, Req, FailedAction, AccFun, More)
             end;
         _ ->
-            call_fold(Hookpoint, Req, AccFun, More)
+            case FailedAction of
+                deny ->
+                    {stop, deny_action_result(Hookpoint, Req)};
+                _ ->
+                    call_fold(Hookpoint, Req, FailedAction, AccFun, More)
+            end
     end.
+
+%% XXX: Hard-coded the deny response
+deny_action_result('client.authenticate', _) ->
+    #{result => false};
+deny_action_result('client.check_acl', _) ->
+    #{result => false};
+deny_action_result('message.publish', Msg) ->
+    %% TODO: Not support to deny a message
+    %% maybe we can put the 'allow_publish' into message header
+    Msg.

apps/emqx_exhook/src/emqx_exhook_mngr.erl

@@ -34,6 +34,8 @@
 %% Helper funcs
 -export([ running/0
         , server/1
+        , put_request_failed_action/1
+        , get_request_failed_action/0
         ]).
 
 %% gen_server callbacks
@@ -100,7 +102,7 @@ call(Pid, Req) ->
 %% gen_server callbacks
 %%--------------------------------------------------------------------
 
-init([Servers, AutoReconnect, ReqOpts]) ->
+init([Servers, AutoReconnect, ReqOpts0]) ->
     process_flag(trap_exit, true),
     %% XXX: Due to the ExHook Module in the enterprise,
     %% this process may start multiple times and they will share this table
@@ -111,7 +113,13 @@ init([Servers, AutoReconnect, ReqOpts]) ->
             ok
     end,
 
+    %% put the global option
+    put_request_failed_action(
+      maps:get(request_failed_action, ReqOpts0, deny)
+     ),
+
     %% Load the hook servers
+    ReqOpts = maps:without([request_failed_action], ReqOpts0),
     {Waiting, Running} = load_all_servers(Servers, ReqOpts),
     {ok, ensure_reload_timer(
            #state{waiting = Waiting,
@@ -272,6 +280,12 @@ clean_reload_timer(Name, State = #state{trefs = TRefs}) ->
 %%--------------------------------------------------------------------
 %% Server state persistent
 
+put_request_failed_action(Val) ->
+    persistent_term:put({?APP, request_failed_action}, Val).
+
+get_request_failed_action() ->
+    persistent_term:get({?APP, request_failed_action}).
+
 save(Name, ServerState) ->
     Saved = persistent_term:get(?APP, []),
     persistent_term:put(?APP, lists:reverse([Name | Saved])),

apps/emqx_exhook/src/emqx_exhook_sup.erl

@@ -47,13 +47,18 @@ init([]) ->
     {ok, {{one_for_one, 10, 100}, [Mngr]}}.
 
 servers() ->
-    application:get_env(emqx_exhook, servers, []).
+    env(servers, []).
 
 auto_reconnect() ->
-    application:get_env(emqx_exhook, auto_reconnect, 60000).
+    env(auto_reconnect, 60000).
 
 request_options() ->
-    #{timeout => application:get_env(emqx_exhook, request_timeout, 5000)}.
+    #{timeout => env(request_timeout, 5000),
+      request_failed_action => env(request_failed_action, deny)
+     }.
+
+env(Key, Def) ->
+    application:get_env(emqx_exhook, Key, Def).
 
 %%--------------------------------------------------------------------
 %% APIs

apps/emqx_exhook/test/emqx_exhook_SUITE.erl

@@ -58,6 +58,26 @@ t_noserver_nohook(_) ->
     ok = emqx_exhook:enable(default),
     ?assertNotEqual([], ets:tab2list(emqx_hooks)).
 
+t_access_failed_if_no_server_running(_) ->
+    emqx_exhook:disable(default),
+    ClientInfo = #{clientid => <<"user-id-1">>,
+                   username => <<"usera">>,
+                   peerhost => {127,0,0,1},
+                   sockport => 1883,
+                   protocol => mqtt,
+                   mountpoint => undefined
+                  },
+    ?assertMatch({stop, #{auth_result := not_authorized}},
+                 emqx_exhook_handler:on_client_authenticate(ClientInfo, #{auth_result => success})),
+
+    ?assertMatch({stop, deny},
+                 emqx_exhook_handler:on_client_check_acl(ClientInfo, publish, <<"t/1">>, allow)),
+
+    Message = emqx_message:make(<<"t/1">>, <<"abc">>),
+    ?assertMatch({stop, Message},
+                 emqx_exhook_handler:on_message_publish(Message)),
+    emqx_exhook:enable(default).
+
 t_cli_list(_) ->
     meck_print(),
     ?assertEqual( [[emqx_exhook_server:format(emqx_exhook_mngr:server(Name)) || Name  <- emqx_exhook:list()]]