Failed to start database plug-in

[wjmwjm000]

{emqx_auth_mysql, {bad_return, {{emqx_auth_mysql_app,start,[normal,[]]}, {'EXIT', {{badmatch, {error, {shutdown, {failed_to_start_child,emqx_auth_mysql, {shutdown, {failed_to_start_child,worker_sup, {shutdown, {failed_to_start_child, {worker,1}, {1045,<<"28000">>, <<"Access denied for user ''@'localhost' (using password: NO)">>}}}}}}}}}, [{emqx_auth_mysql_app,start,2, [{file,"emqx_auth_mysql_app.erl"},{line,38}]}, {application_master,start_it_old,4, [{file,"application_master.erl"},{line,277}]}]}}}}}

[HJianBo]

"Access denied for user ''@'localhost' (using password: NO)"

You should check these configurations for MySQL authentication in etc/plugins/emqx_auth_mysql.conf:

## MySQL username.
##
## Value: String
auth.mysql.username = your-mysql-username

## MySQL password.
##
## Value: String
auth.mysql.password = your-mysql-password

## MySQL database.
##
## Value: String
auth.mysql.database = mqtt