1. globalLock，关键是看一下PRIMARY节点上的参数
"globalLock" : {
                                 "totalTime" : 47279680356,
                                 "lockTime" : 1586763,
                                 "ratio" : 0.00003356120405324679,
                                 "currentQueue" : {
                                                 "total" : 0,
                                                 "readers" : 0,
                                                 "writers" : 0
                                },
                                 "activeClients" : {
                                                 "total" : 2,
                                                 "readers" : 2,
                                                 "writers" : 0
                                }
                },

activeClients表示中可以看出slave有两个，这个值在slave上始终为0
2. connections客户端连接数
Master上的
"connections" : {
         "current" : 9,
         "available" : 810
},
Slave上的
"connections" : {
     "current" : 16,
     "available" : 803
},
在客户端增加读取线程后，Master上不会变，而Slave上会增加

3. opcounters
Master上
"opcounters" : {
         "insert" : 7,
         "query" : 1215,
         "update" : 33,
         "delete" : 1,
         "getmore" : 32558,
         "command" : 48141
},
Slave上
"opcounters" : {
             "insert" : 0,
             "query" : 4971,
             "update" : 0,
             "delete" : 0,
             "getmore" : 0,
             "command" : 44342
},
可以看到insert、update、delete是在Master上，查询是在slave上，可以检查master-slave设置是否正确，注意要先执行过rs.slaveOk()