Mac下mongodb connect failed 连接错误解决方法

这几天一直在折腾mongodb数据库，一直出现如下这个问题

MongoDB shell version v3.6.0
connecting to: mongodb://127.0.0.1:27017
2017-12-27T09:54:34.775+0800 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: Connection refused
2017-12-27T09:54:34.778+0800 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed :
connect@src/mongo/shell/mongo.js:237:13
@(connect):1:6
exception: connect failed

尝试各种方法都不行

当mongodb service 没有运行的时候会发生这样的错误

尝试了新建一个/data/db 目录，也不奏效。

后来通过搜索，寻找到来解决方法，运行命令

brew services start mongodb

再去调用数据库命令

mongo

就可以完美解决问题了

最终mac下显示成功的提示

MongoDB shell version v3.6.0
connecting to: mongodb://127.0.0.1:27017
MongoDB server version: 3.6.0
Server has startup warnings: 
2017-12-27T09:54:58.316+0800 I CONTROL  [initandlisten] 
2017-12-27T09:54:58.316+0800 I CONTROL  [initandlisten] ** WARNING: Access control is not enabled for the database.
2017-12-27T09:54:58.316+0800 I CONTROL  [initandlisten] **          Read and write access to data and configuration is unrestricted.
2017-12-27T09:54:58.316+0800 I CONTROL  [initandlisten] 
>