有一个复制集由一个primary和三个sencondary组成

primary：10.0.1.32
secondary：10.0.1.31 、10.0.1.33、192.168.1.230

rs.status()显示
rs.status()
{
    ......
        "members" : [
        {
            "_id" : 0,
            "name" : "10.0.1.31:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "SECONDARY",
            ......
        },
        {
            "_id" : 1,
            "name" : "10.0.1.32:27017",
            "health" : 1,
            "state" : 5,
            "stateStr" : "PRIMARY",
            ......
        },
        {
            "_id" : 2,
            "name" : "192.168.1.230:27017",
            "health" : 1,
            "state" : 5,
            "stateStr" : "SECONDARY",
            ......
        },
        {
            "_id" : 3,
            "name" : "10.0.1.33:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            ......
        }
    ],
    "ok" : 1
}

切换目标：31升级为primary，32降级为secondary

primary：10.0.1.31 secondary：10.0.1.32 、10.0.1.33、192.168.1.230 切换步骤(均在mongodb shell上执行)

1、primary上设定各个节点优先级
cfg = rs.conf()
cfg.members[0].priority = 1
cfg.members[1].priority = 0.5
cfg.members[2].priority = 0.5
cfg.members[3].priority = 0.5
rs.reconfig(cfg)

2、33和230节点上执行rs.freeze（120）命令，阻止其在120秒内成为primary节点
rs.freeze(120)

3、primary上执行降级命令,使其120秒内不再成为primary
rs.stepDown(120)

4、观察31节点发现已经成为primary
rs.status()
{
    ......
        "members" : [
        {
            "_id" : 0,
            "name" : "10.0.1.31:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            ......
        },
        {
            "_id" : 1,
            "name" : "10.0.1.32:27017",
            "health" : 1,
            "state" : 5,
            "stateStr" : "SECONDARY",
            ......
        },
        {
            "_id" : 2,
            "name" : "192.168.1.230:27017",
            "health" : 1,
            "state" : 5,
            "stateStr" : "SECONDARY",
            ......
        },
        {
            "_id" : 3,
            "name" : "10.0.1.33:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            ......
        }
    ],
    "ok" : 1
}

切换成功