使用 authenticationDatabase 參數鏈接 aliyun 上的 MongoDB

一般，命令行 鏈接 MongoDB 咱們是這麼作的：

mongo -u <user> -p <pass> --host <host> --port 28015

或者使用標準的鏈接字符串地址URI:

mongodb://[username:password@]host1[:port1][,...hostN[:portN]][/[database][?options]]

# 例如
mongo mongodb://127.0.0.1:27017

當鏈接主從數據庫時候也能夠直接使用，例如某些雲服務器提供商的數據庫鏈接方式：

mongo mongodb://root:password@dds-0xi1234.mongodb.rds.aliyuncs.com:3717,dds-0xi5678.mongodb.rds.aliyuncs.com:3717/admin

直接使用這種通用的地址字符串是很是方便的，無論是獨立數據庫、副本集以及集羣都是統一的，格式大概是這樣的：
mongodb://[username:password@]host1[:port1][,...hostN[:portN]][/[database][?options]]

可是，mongo 命令行客戶端能夠使用，其餘的一些工具就沒有辦法直接用了，好比mongotop,mongofiles等等：

# grid fs 操做
root@server:~# mongofiles mongodb://ubuntu:password@IP_ADDR:27017/admin
2019-08-12T20:39:52.764+0800    'mongodb://ubuntu:password@IP_ADDR:27017/admin' is not a valid command
2019-08-12T20:39:52.765+0800    try 'mongofiles --help' for more information

# mongo top
root@server:~# mongotop mongodb://ubuntu:password@IP_ADDR:27017/admin
2019-08-12T20:44:39.874+0800    invalid sleep time: mongodb://ubuntu:password@IP_ADDR:27017/admin

查了一下文檔，阿里雲上購買的這種叫作 Authentication Database¶ 的數據庫，須要使用 --authenticationDatabase 參數來操做：

Authentication Database 的說明是這樣的：

Authentication Database¶
When adding a user, you create the user in a specific database. This database is the authentication database for the user.

A user can have privileges across different databases; that is, a user’s privileges are not limited to their authentication database. By assigning to the user roles in other databases, a user created in one database can have permissions to act on other databases. For more information on roles, see Role-Based Access Control.

The user’s name and authentication database serve as a unique identifier for that user. [1] That is, if two users have the same name but are created in different databases, they are two separate users. If you intend to have a single user with permissions on multiple databases, create a single user with roles in the applicable databases instead of creating the user multiple times in different databases.

對於這樣的數據庫，若是咱們要使用 db 自帶那一族工具來操做的話能夠這樣：

mongofiles --host dds-0xi1234.mongodb.rds.aliyuncs.com:3717 --authenticationDatabase admin -d xxx list
mongotop --host dds-0xi1234.mongodb.rds.aliyuncs.com:3717 --authenticationDatabase admin
mongostat --host dds-0xi1234.mongodb.rds.aliyuncs.com:3717 --authenticationDatabase admin