今天早上遇到code4app.com报错信息：
Fatal error: Uncaught exception 'MongoConnectionException' with message 'Failed to connect to: localhost:27017: Connection refused' in /data/wwwroot/www.code4app.com/app/libraries/Mongo.php:21 Stack trace: #0 /data/wwwroot/www.code4app.com/app/libraries/Mongo.php(21): Mongo->__construct('mongodb://local...') #1 /data/wwwroot/www.code4app.com/sys/core/Loader.php(1007): CI_Mongo->__construct(Array) #2 /data/wwwroot/www.code4app.com/sys/core/Loader.php(888): CI_Loader->_ci_init_class('Mongo', '', NULL, NULL) #3 /data/wwwroot/www.code4app.com/sys/core/Loader.php(138): CI_Loader->_ci_load_class('mongo', NULL, NULL) #4 /data/wwwroot/www.code4app.com/app/libraries/Collection.php(9): CI_Loader->library('mongo') #5 /data/wwwroot/www.code4app.com/app/libraries/User.php(16): Collection->__construct('user') #6 /data/wwwroot/www.code4app.com/sys/core/Loader.php(1011): User->__construct() #7 /data/wwwroot/www.code4app.com/sys/core/Loader.php(888): CI_Loader->_ci_init_class('User', '', NULL, NULL) #8 /data/wwwroot/www.code4app.com/sys/c in /data/wwwroot/www.code4app.com/app/libraries/Mongo.php on line 21