监控思路：一个是集群成员的健康状态，一个是连接数

1.通过命令rs.status()进行集群内成员健康

MongoDB Enterprise config-rs:PRIMARY> rs.status()
{
        "set" : "config-rs",       # 副本集已经配置成功
        "date" : ISODate("2019-11-23T04:56:35.588Z"),
        "myState" : 1,
        "term" : NumberLong(1),
        "syncingTo" : "",
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "configsvr" : true,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 2,
        "writeMajorityCount" : 2,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1574484982, 1),
                        "t" : NumberLong(1)
                },
                "lastCommittedWallTime" : ISODate("2019-11-23T04:56:22.464Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1574484982, 1),
                        "t" : NumberLong(1)
                },
                "readConcernMajorityWallTime" : ISODate("2019-11-23T04:56:22.464Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1574484982, 1),
                        "t" : NumberLong(1)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1574484982, 1),
                        "t" : NumberLong(1)
                },
                "lastAppliedWallTime" : ISODate("2019-11-23T04:56:22.464Z"),
                "lastDurableWallTime" : ISODate("2019-11-23T04:56:22.464Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1574484952, 30),
        "lastStableCheckpointTimestamp" : Timestamp(1574484952, 30),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2019-11-23T04:55:51.134Z"),
                "termAtElection" : NumberLong(1),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1574484951, 1),
                        "t" : NumberLong(-1)
                },
                "numVotesNeeded" : 1,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "newTermStartDate" : ISODate("2019-11-23T04:55:52.141Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2019-11-23T04:55:52.266Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "worker2:27018",
                        "ip" : "192.168.255.134",
                        "health" : 1,         # 监控该值，不是1就实现告警
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 722,
                        "optime" : {
                                "ts" : Timestamp(1574484982, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2019-11-23T04:56:22Z"),
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "could not find member to sync from",
                        "electionTime" : Timestamp(1574484951, 2),
                        "electionDate" : ISODate("2019-11-23T04:55:51Z"),
                        "configVersion" : 2,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "worker2:27019",
                        "ip" : "192.168.255.134",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 13,
                        "optime" : {
                                "ts" : Timestamp(1574484982, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1574484982, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2019-11-23T04:56:22Z"),
                        "optimeDurableDate" : ISODate("2019-11-23T04:56:22Z"),
                        "lastHeartbeat" : ISODate("2019-11-23T04:56:34.705Z"),
                        "lastHeartbeatRecv" : ISODate("2019-11-23T04:56:35.176Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncingTo" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 2
                }
        ],
        "ok" : 1,
        "$gleStats" : {
                "lastOpTime" : {
                        "ts" : Timestamp(1574484982, 1),
                        "t" : NumberLong(1)
                },
                "electionId" : ObjectId("7fffffff0000000000000001")
        },
        "lastCommittedOpTime" : Timestamp(1574484982, 1),
        "$clusterTime" : {
                "clusterTime" : Timestamp(1574484982, 1),
                "signature" : {
                        "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
                        "keyId" : NumberLong(0)
                }
        },
        "operationTime" : Timestamp(1574484982, 1)
}

分段说明
set
当前副本集名称
date
执行命令时间
myState
当前节点的状态(角色)
syncingTo
同步源
heartbeatIntervalMillis
心跳间隔
members
节点成员
members.id
成员编号
members.name
成员名称
members.heath
健康状态，1-true,0-false 监控该值，为0结合zabbix则告警
members.state
成员状态(角色)1-主节点 2-备节点 7-仲裁节点
members.stateStr
成员状态名
members.uptime
成员启动运行时长
members.optime
成员oplog时间戳(字段ts)
members.optimeDate
成员oplog时间(格式化)
members.lastHeartbeat
当前节点对成员的最后一个心跳
members.lastHeartbeatRecv
当前节点收到该成员的最后一个心跳
members.pingMs
当前节点到该成员的回路时长
members.syncingTo
成员同步源
members.electionTime
主节点选举时间戳(ms)
members.electionDate
主节点选举时间(格式化)

2.通过mongostat监控conn连接数字段

$ mongostat --host 192.168.255.134 --port 27017  -u adminUser -p adminPass --authenticationDatabase="admin" —json

{"192.168.255.134:27017":{"arw":"1|0","command":"2|0","conn":"2","delete":"*0","dirty":"0.0%","flushes":"0","getmore":"0","insert":"*0","net_in":"167b","net_out":"35.4k","qrw":"0|0","query":"*0","res":"83.0M","time":"14:27:26","update":"*0","used":"0.0%","vsize":"1.52G"}}

3.可以引入pymongo模块进行监控，具体脚本就不贴出了，比较简单。连接数默认大于2000就有问题，也可以结合zabbix进行自定义监控，大于2000的连接数就触发告警。监控脚本为python，过几天贴上