mongodb副本集原理及部署记录

工作原理

MongoDB的复制是基于操作日志oplog，相当于MySQL中的二进制日志，只记录发生改变的记录。复制是将主节点的oplog日志同步并应用到其他从节点的过程。

1.副本集之间的复制是通过oplog日志现实的.备份节点通过查询这个集合就可以知道需要进行复制的操作

2.oplog是节点中local库中的一个固定的集合,在默认情况下oplog初始化大小为空闲磁盘的5%.oplog是capped collection,所以当oplog的空间被占满时,会覆盖最初写入的日志

3.通过改变oplog文档的大小直接改变local所占磁盘空间的大小.可以在配置文件中设置oplogSize参数来指定oplog文档的大小。

4.通过oplog中的操作记录,把数据复制在备份节点.

5.主节点是集中接收写入操作的,MongoDB中的应用连接到主节点进行写入操作，然后记录在主节点操作oplog,从节点成员定期轮询复制此日志并将操作应用于其数据集。

常用命令

rs.conf()   查看副本集配置

rs.status()  查看副本集状态

rs.initiate(config)   初始化副本集

rs.isMaster()   查看是否为主节点

db.getMongo().setSlaveOk();   赋予副本集副本节点查询数据的权限，副本节点执行

rs.add("ip:port")   新增副本集节点

rs.remove("ip:port")  删除副本集节点

rs.addArb("ip:port")    添加仲裁节点

副本集参数说明

"_id":            #集群中节点编号
"name":           #成员服务器名称及端口
"health" :          #表示成员中的健康状态（0:down;1:up）
"state" :          #为0~10，表示成员的当前状态
"stateStr" :        #描述该成员是主库（PRIMARY）还是备库（SECONDARY）
"uptime" :          #该成员在线时间（秒）
"optime" :          #成员最后一次应用日志(oplog)的信息
"optimeDate" :       #成员最后一次应用日志(oplog)的时间
"electionTime" :      #当前primary从操作日志中选举信息
"electionDate" :      #当前primary被选定为primary的日期
"configVersion" :     #mongodb版本
"self" :           #为true 表示当前节点 

开始部署mongod副本集

一、环境准备

操作系统centos6.5 mongodb版本3.6.6

ip地址                  主机名                    角色

192.168.1.230       mongodb01          副本集主节点

192.168.1.18        mongodb02           副本集副本节点

192.168.1.247      mongodb03           副本集副本节点

关闭3个服务器的防火墙及selinux

二、安装部署mongodb及副本集配置

1、安装部署mongodb

可参考：https://www.cnblogs.com/wusy/p/10405991.html

2、副本集配置

1）yum安装mongodb在做副本集时需在所有服务器配置文件加入以下配置：

replication:
   replSetName: repset（副本集名，可自定义）   #副本集配置

security:                  #开启副本集用户认证
   authorization: enabled
   keyFile: /data/mongodb/keyfile
   clusterAuthMode: keyFile

2）源码包构建副本集时，则需加以下语法来配置：

replSet=repset（副本集名）  #副本集配置

auth=true   #开启副本集用户认证，若为单击模式，则不创建和指定秘钥文件
keyFile=/data2/mongodb-3.6.6/keyfile  #指定秘钥文件路径

journal=true  #开启journal日志，默认为开启

3、初始化副本集

在任意一台节点初始化都可，但在哪一台做初始化，那么这一台就作为副本集的主节点，这里选择mongodb01（也可使用权重值来控制主副节点）

1）进入mongodb数据库

[root@mongodb01 ~]# mongo --host 192.168.1.230

2）定义副本集配置，这里的_id:repset要与配置文件中所指的副本集名称一致

 >config={
 ... _id:"repset",   #务必与配置文件中指定的副本集名称一致
 ... members:[
 ... {_id:,host:"192.168.1.230:27017"},
 ... {_id:,host:"192.168.1.18:27017"},
 ... {_id:,host:"192.168.1.247:27017"}
 ... ]
 ... }

 {
 "_id" : "repset",
 "members" : [
 {
 "_id" : ,
 "host" : "192.168.1.230:27017"
 },
 {
 "_id" : ,
 "host" : "192.168.1.18:27017"
 },
 {
 "_id" : ,
 "host" : "192.18.1.247:27017"
 }
 ]
 }

3)初始化副本集配置

 > rs.initiate(config)
 {
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

4）查看集群节点状态（health为1表明正常，为0表明异常）

 repset:PRIMARY> rs.status()
 {
 "set" : "repset",
 "date" : ISODate("2019-03-02T04:50:47.554Z"),
 "myState" : ,
 "term" : NumberLong(),
 "syncingTo" : "",
 "syncSourceHost" : "",
 "syncSourceId" : -,
 "heartbeatIntervalMillis" : NumberLong(),
 "optimes" : {
 "lastCommittedOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "readConcernMajorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "appliedOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "durableOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 }
 },
 "lastStableCheckpointTimestamp" : Timestamp(, ),
 "members" : [
 {
 "_id" : ,
 "name" : "192.168.1.230:27017",
 "health" : ,
 "state" : ,
 "stateStr" : "PRIMARY",
 "uptime" : ,
 "optime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "optimeDate" : ISODate("2019-03-02T04:50:38Z"),
 "syncingTo" : "",
 "syncSourceHost" : "",
 "syncSourceId" : -,
 "infoMessage" : "could not find member to sync from",
 "electionTime" : Timestamp(, ),
 "electionDate" : ISODate("2019-03-02T04:50:07Z"),
 "configVersion" : ,
 "self" : true,
 "lastHeartbeatMessage" : ""
 },
 {
 "_id" : ,
 "name" : "192.168.1.18:27017",
 "health" : ,
 "state" : ,
 "stateStr" : "SECONDARY",
 "uptime" : ,
 "optime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "optimeDurable" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "optimeDate" : ISODate("2019-03-02T04:50:38Z"),
 "optimeDurableDate" : ISODate("2019-03-02T04:50:38Z"),
 "lastHeartbeat" : ISODate("2019-03-02T04:50:47.382Z"),
 "lastHeartbeatRecv" : ISODate("2019-03-02T04:50:46.242Z"),
 "pingMs" : NumberLong(),
 "lastHeartbeatMessage" : "",
 "syncingTo" : "192.168.1.247:27017",
 "syncSourceHost" : "192.168.1.247:27017",
 "syncSourceId" : ,
 "infoMessage" : "",
 "configVersion" :
 },
 {
 "_id" : ,
 "name" : "192.168.1.247:27017",
 "health" : ,
 "state" : ,
 "stateStr" : "SECONDARY",
 "uptime" : ,
 "optime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "optimeDurable" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "optimeDate" : ISODate("2019-03-02T04:50:38Z"),
 "optimeDurableDate" : ISODate("2019-03-02T04:50:38Z"),
 "lastHeartbeat" : ISODate("2019-03-02T04:50:47.382Z"),
 "lastHeartbeatRecv" : ISODate("2019-03-02T04:50:46.183Z"),
 "pingMs" : NumberLong(),
 "lastHeartbeatMessage" : "",
 "syncingTo" : "192.168.1.230:27017",
 "syncSourceHost" : "192.168.1.230:27017",
 "syncSourceId" : ,
 "infoMessage" : "",
 "configVersion" :
 }
 ],
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }
 repset:PRIMARY>

5）查看是否为主节点（可在其他节点执行查看）

 repset:PRIMARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.230:27017",
 "192.168.1.18:27017",
 "192.168.1.247:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
 "ismaster" : true,
 "secondary" : false,
 "primary" : "192.168.1.230:27017",
 "me" : "192.168.1.230:27017",
 "electionId" : ObjectId("7fffffff0000000000000001"),
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T04:52:28Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T04:52:28Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T04:52:32.106Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

6）可登入副本集副本节点，并查看是否为主节点或副本节点

 [root@mongodb02 ~]# mongo --host 192.168.1.18

 repset:SECONDARY>

 repset:SECONDARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.230:27017",
 "192.168.1.18:27017",
 "192.168.1.247:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
 "ismaster" : false,
 "secondary" : true,
 "primary" : "192.168.1.230:27017",
 "me" : "192.168.1.18:27017",
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T04:54:18Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T04:54:18Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T04:54:27.819Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

三、登入副本集副本集节点验证数据复制功能（默认副本集的副本节点不能查看数据）

1、在主节点mongodb01上插入数据，在副本节点查看数据

 repset:PRIMARY> use test
 switched to db test

 repset:PRIMARY> db.test.save({id:"one",name:"wushaoyu"})
 WriteResult({ "nInserted" :  })

2、进入副本节点mongodb02查看主库插入的数据

 repset:SECONDARY> use test
 switched to db test
 repset:SECONDARY> show dbs
 --02T13::06.503+ E QUERY [js] Error: listDatabases failed:{
 "operationTime" : Timestamp(, ),
 "ok" : ,
 "errmsg" : "not master and slaveOk=false",
 "code" : ,
 "codeName" : "NotMasterNoSlaveOk",
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 } :
 _getErrorWithCode@src/mongo/shell/utils.js::
 Mongo.prototype.getDBs@src/mongo/shell/mongo.js::
 shellHelper.show@src/mongo/shell/utils.js::
 shellHelper@src/mongo/shell/utils.js::
 @(shellhelp2)::

注：上面出现了报错

因为主库插入的数据，从库是不具备读的权限的，所以要设置副本节点可以读

 repset:SECONDARY> db.getMongo().setSlaveOk();

 repset:SECONDARY> db.test.find()
 { "_id" : ObjectId("5c7a0f3a6698c70ef075f0a8"), "id" : "one", "name" : "wushaoyu" }

 repset:SECONDARY> show tables
 test

注：由此看到，副本节点已经把主节点的数据复制过来了（在mongodb03上做同样操作即可）

四、验证故障转移功能，停止当前副本主节点，验证高可用

先停止副本主节点，在查看副本节点的状态，

1）停止副本主节点的mongodb

 [root@mongodb01 ~]# ps -ef |grep mongod
 mongod    : ? :: /usr/bin/mongod -f /etc/mongod.conf
 root    : pts/ :: grep mongod

 [root@mongodb01 ~]# kill - 

2）登录其他两个副本集节点，查看是否推选出新的主节点

 [root@mongodb02 ~]# mongo --host 192.168.1.18

 repset:SECONDARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.230:27017",
 "192.168.1.18:27017",
 "192.168.1.247:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
12 "ismaster" : false,
13 "secondary" : true,
14 "primary" : "192.168.1.247:27017",
15 "me" : "192.168.1.18:27017",
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T05:16:41Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T05:16:41Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T05:16:48.433Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

 [root@mongodb03 ~]# mongo --host 192.168.1.247

 repset:PRIMARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.230:27017",
 "192.168.1.18:27017",
 "192.168.1.247:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
58 "ismaster" : true,
59 "secondary" : false,
60 "primary" : "192.168.1.247:27017",
61 "me" : "192.168.1.247:27017",
 "electionId" : ObjectId("7fffffff0000000000000002"),
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T05:19:31Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T05:19:31Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T05:19:35.282Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

ps：发现主节点宕机之后，mongodb03为新推选出来的主节点

3）在新的主节点mongodb03插入数据，在mongodb02上查看是否同步

 [root@mongodb03 ~]# mongo --host 192.168.1.247

 repset:PRIMARY> use wsy
 switched to db wsy
 repset:PRIMARY> db.wsy.save({"name":"wsy"})
 WriteResult({ "nInserted" :  })

 [root@mongodb02 ~]# mongo --host 192.168.1.18

 repset:SECONDARY> db.getMongo().setSlaveOk();
 repset:SECONDARY> show tables
 wsy

 repset:SECONDARY> db.wsy.find()
 { "_id" : ObjectId("5c7a133007ebf60ac5870bae"), "name" : "wsy" }

由此可看出，数据同步成功

4）启动先前的mongodb01，查看状态，mongodb成为了当前主节点的副本节点，并且在它宕机期间插入的数据也同步了过来

 [root@mongodb01 ~]# /etc/init.d/mongod start

 [root@mongodb01 ~]# mongo --host 192.168.1.230

 repset:SECONDARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.230:27017",
 "192.168.1.18:27017",
 "192.168.1.247:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
14 "ismaster" : false,
15 "secondary" : true,
16 "primary" : "192.168.1.247:27017",
17 "me" : "192.168.1.230:27017",
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T05:32:51Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T05:32:51Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T05:32:59.225Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

#开启副本节点读的权限

 repset:SECONDARY> db.getMongo().setSlaveOk();
 repset:SECONDARY> db.wsy.find()
 { "_id" : ObjectId("5c7a133007ebf60ac5870bae"), "name" : "wsy" }

注：在原来的主节点宕机期间，新选举出来的主机插入的数据，也会同步过来

五、java程序连接副本集测试

public class TestMongoDBReplSet {

        public static void main(String[] args) {

               try {
                     List<ServerAddress> addresses = new ArrayList<ServerAddress>();
                     ServerAddress address1 = new ServerAddress("192.168.1.230" , );
                     ServerAddress address2 = new ServerAddress("192.168.1.18" , );
                     ServerAddress address3 = new ServerAddress("192.168.1.247" , );
                     addresses.add(address1);
                     addresses.add(address2);
                     addresses.add(address3);

                     MongoClient client = new MongoClient(addresses);
                     DB db = client.getDB( "test");
                     DBCollection coll = db.getCollection( "testdb");

                      // 插入
                     BasicDBObject object = new BasicDBObject();
                     object.append( "test2", "testval2" );

                     coll.insert(object);

                     DBCursor dbCursor = coll.find();

                      while (dbCursor.hasNext()) {
                           DBObject dbObject = dbCursor.next();
                           System. out.println(dbObject.toString());
                     }

              } catch (Exception e) {
                     e.printStackTrace();
              }

       }

}

目前看起来支持完美的故障转移了，这个架构是不是比较完美了？其实还有很多地方可以优化

六、副本集开启用户认证模式

1、创建keyFile文件

keyFile文件的作用： 集群之间的安全认证，增加安全认证机制KeyFile（开启keyfile认证就默认开启了auth认证了，为了保证后面可以登录，我已创建了用户）

openssl rand -base64  > /root/keyfile    

　其中666是文件大小           /root/keyfile ： 文件存放路径

##该key的权限必须是600；也可改为400

　　　chmod 600 /root/keyfile

注：创建秘钥文件可添置mongodb副本集，在创建，防止服务无法启动等原因

2、修改配置文件

security:
  authorization: enabled
  keyFile: /root/keyfile
  clusterAuthMode: keyFile

3、重新启动mongodb节点

[root@ecs-1e54- ~]# mongod -f /etc/mongod.conf
--20T13::11.479+ I CONTROL  [main] Automatically disabling TLS 1.0, to force-enable TLS 1.0 specify --sslDisabledProtocols 'none'
about to fork child process, waiting until server is ready for connections.
forked process:
child process started successfully, parent exiting

注：此处启动需使用这种指定文件的方式启动。因为本人安装mongodb采用rpm包安装，故启动是可用/etc/init.d/mongod start的方式启动，但是在副本集开启了用户认证的方式下，在采取这种启动方式，因为启动脚本的内容原因，就会报错permission denied，导致启动服务失败。

4、连接验证

[root@ecs-2c32 mongodb]# mongo 192.168.1.193:
MongoDB shell version v4.0.0
connecting to: mongodb://192.168.1.193:27017/test
MongoDB server version: 4.0.
repset:PRIMARY> show dbs
--20T13::49.421+ E QUERY    [js] Error: listDatabases failed:{
    "operationTime" : Timestamp(, ),
    "ok" : ,
    "errmsg" : "command listDatabases requires authentication",
    "code" : ,
    "codeName" : "Unauthorized",
    "$clusterTime" : {
        "clusterTime" : Timestamp(, ),
        "signature" : {
            "hash" : BinData(,"hKSQT5ImwURihIb0w/CeT4vu44E="),
            "keyId" : NumberLong("")
        }
    }
} :
_getErrorWithCode@src/mongo/shell/utils.js::
Mongo.prototype.getDBs@src/mongo/shell/mongo.js::
shellHelper.show@src/mongo/shell/utils.js::
shellHelper@src/mongo/shell/utils.js::
@(shellhelp2)::

可看出此处需要用户认证方可查看数据

repset:PRIMARY> use admin
switched to db admin
repset:PRIMARY> db.auth('admin','admin')

repset:PRIMARY> show dbs
admin   .000GB
config  .000GB
local   .000GB

七、仲裁节点

副本集只能由主节点来接收写操作，而副本节点可以专门用来读操作

当副本节点增多时，主节点的复制压力就会增大，这是就可以添加仲裁节点

在副本集里，仲裁节点仲裁节点不存储数据，只是负责故障转移的群体投票，这样就少了数据复制的压力

1）添加仲裁节点192.168.1.7

 repset:PRIMARY> rs.addArb("192.168.1.7:27017")
 {
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

2）查看节点信息

 repset:PRIMARY> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.18:27017",
 "192.168.1.247:27017",
 "192.168.1.230:27017"
 ],
 "arbiters" : [
 "192.168.1.7:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
13 "ismaster" : true,
14 "secondary" : false,
15 "primary" : "192.168.1.18:27017",
16 "me" : "192.168.1.18:27017",
 "electionId" : ObjectId("7fffffff0000000000000003"),
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T09:38:33Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T09:38:33Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T09:38:45.054Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" : ,
 "operationTime" : Timestamp(, ),
 "$clusterTime" : {
 "clusterTime" : Timestamp(, ),
 "signature" : {
 "hash" : BinData(,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
 "keyId" : NumberLong()
 }
 }
 }

3）登录仲裁节点查看状态

 repset:ARBITER> db.getMongo().setSlaveOk();
 repset:ARBITER> rs.isMaster()
 {
 "hosts" : [
 "192.168.1.18:27017",
 "192.168.1.247:27017",
 "192.168.1.230:27017"
 ],
 "arbiters" : [
 "192.168.1.7:27017"
 ],
 "setName" : "repset",
 "setVersion" : ,
 "ismaster" : false,
 "secondary" : false,
 "primary" : "192.168.1.18:27017",
 "arbiterOnly" : true,
 "me" : "192.168.1.7:27017",
 "lastWrite" : {
 "opTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "lastWriteDate" : ISODate("2019-03-02T09:43:10Z"),
 "majorityOpTime" : {
 "ts" : Timestamp(, ),
 "t" : NumberLong()
 },
 "majorityWriteDate" : ISODate("2019-03-02T09:43:10Z")
 },
 "maxBsonObjectSize" : ,
 "maxMessageSizeBytes" : ,
 "maxWriteBatchSize" : ,
 "localTime" : ISODate("2019-03-02T09:43:14.154Z"),
 "logicalSessionTimeoutMinutes" : ,
 "minWireVersion" : ,
 "maxWireVersion" : ,
 "readOnly" : false,
 "ok" :
 }