fix mysql auth error

apps/emqttd/src/emqttd_access_control.erl

@@ -179,6 +179,7 @@ handle_call({register_mod, Type, Mod, Opts}, _From, State) ->
                     ets:insert(?ACCESS_CONTROL_TAB, {tab_key(Type), [{Mod, ModState}|Mods]}),
                     ok;
                 {'EXIT', Error} ->
+                    lager:error("Access Control: register ~s error - ~p", [Mod, Error]),
                     {error, Error}
             end;
         _ -> 

plugins/emqttd_auth_mysql/etc/plugin.config

@@ -9,8 +9,9 @@
 ]},
 {emqttd_auth_mysql, [
    {users_table, mqtt_users},
+   {password_hash, plain},
    {field_mapper, [
        {username, username},
-       {password, password, plain}
+       {password, password}
    ]}
 ]}

plugins/emqttd_auth_mysql/src/emqttd_auth_mysql.erl

@@ -38,15 +38,19 @@
 
 init(Opts) -> 
     Mapper = proplists:get_value(field_mapper, Opts),
-    {ok, #state{user_table  = proplists:get_value(user_table, Opts, mqtt_users),
+    {ok, #state{user_table = proplists:get_value(user_table, Opts),
                 name_field = proplists:get_value(username, Mapper),
                 pass_field = proplists:get_value(password, Mapper),
-                pass_hash = proplists:get_value(Opts, password_hash)}}.
+                pass_hash  = proplists:get_value(password_hash, Opts)}}.
 
 check(#mqtt_client{username = undefined}, _Password, _State) ->
     {error, "Username undefined"};
+check(#mqtt_client{username = <<>>}, _Password, _State) ->
+    {error, "Username undefined"};
 check(_Client, undefined, _State) ->
     {error, "Password undefined"};
+check(_Client, <<>>, _State) ->
+    {error, "Password undefined"};
 check(#mqtt_client{username = Username}, Password,
       #state{user_table = UserTab, pass_hash = Type,
              name_field = NameField, pass_field = PassField}) ->

plugins/emqttd_auth_mysql/src/emqttd_auth_mysql_app.erl

@@ -40,7 +40,7 @@
 
 start(_StartType, _StartArgs) ->
     Env = application:get_all_env(),
-    emqttd_access_control:register_mod(auth, emqttd_auth_mysql, Env),
+    ok = emqttd_access_control:register_mod(auth, emqttd_auth_mysql, Env),
     supervisor:start_link({local, ?MODULE}, ?MODULE, []).
 
 prep_stop(State) ->

rel/files/plugins.config

@@ -9,7 +9,12 @@
 %    {encoding, utf8}
 % ]},
 % {emqttd_auth_mysql, [
-%    {user_table, mqtt_users}
+%     {users_table, mqtt_users},
+%     {password_hash, plain},
+%     {field_mapper, [
+%         {username, username},
+%         {password, password}
+%     ]}
 % ]}
 %
 % {emqttd_dashboard, [