mongodb主从切换

DESC

我们使用的是阿里云mongodb，需要配置两个主从ip（例如下面192.168.10.2，192.168.10.3）
问题：第一个节点（192.168.10.2）挂掉之后不会自动切换到第二个节点（192.168.10.3）

db: {
    type: 'mongo',
    log_sql: true,
    log_connect: true,
    adapter: {
      mongo: {
        host: ['192.168.10.2','192.168.10.3'],
        port: ['3717'],
        database: 'dev',
        prefix: '',
        user: 'root',
        password: '123456',
        options: {
          authSource: "admin"
        },
        server: {
          poolSize: 1
        }
      }
    }
  }

ENV

Platform:
centos6
Node.js Version:
v6.3.1
ThinkJS Version:
v2.2.15

Start from the Mongo adapter configuration shown in the issue and reproduce the failure using the stated CentOS 6 and Node.js v6.3.1 environment. Trace how the two hosts and port are handled; done means that losing 192.168.10.2 automatically moves connections to 192.168.10.3. No source file or test is named, so locating the adapter entry point is part of the work.