MongoDB副本（一主一备+仲裁）环境部署记录

洗尽了浮华

发布于 2018-01-23 15:48:07

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发布于 2018-01-23 15:48:07

MongoDB复制集是一个带有故障转移的主从集群。是从现有的主从模式演变而来，增加了自动故障转移和节点成员自动恢复。 MongoDB复制集模式中没有固定的主结点，在启动后，多个服务节点间将自动选举产生一个主结点。该主结点被称为primary，一个或多个从结点被称为secondaries。 primary结点基本上就是master结点，不同之处在于primary结点在不同时间可能是不同的服务器。如果当前的主结点失效了，复制集中的其余结点将会试图选出一个新的主结点。

MongoDB复制集模式的好处：

一切自动化。首先，复制集模式本身做了大量的管理工作，自动管理从节点，确保数据不会不一致。
主节点挂掉后，会自动判断集群中的服务器并进行故障转移，推举新的主节点。
一个复制集集群支持1-7台服务器，在一个复制集中各个服务器数据保持完全一致。

在一个MongoDB复制集集群中，各个服务器有以下几种状态：

Primary 主节点，一个复制集有且仅有一台服务器处于Primary状态，只有主节点才对外提供读写服务。如果主节点挂掉，复制集将投票选出一个备节点成为新的主节点。
Secondary 备用节点，复制集允许有多台Secondary，每个备用节点的数据与主节点的数据是完全同步的。Recovering 恢复中，当复制集中某台服务器挂掉或者掉线后数据无法同步，重新恢复服务后从其他成员复制数据，这时就处于恢复过程，数据同步后，该节点又回到备用状态。
Arbiter 仲裁节点，该类节点可以不用单独存在，如果配置为仲裁节点，就主要负责在复本集中监控其他节点状态，投票选出主节点。该节点将不会用于存放数据。如果没有仲裁节点，那么投票工作将由所有节点共同进行。
Down 无效节点，当服务器挂掉或掉线时就会处于该状态。复制集的从节点读请求，也是在各个Driver层设置slaveOk的值来实现的。

如上介绍所知，mongodb中的复制可以在多台服务器中同步数据。复制提供了冗余和增加了数据的高可用性，防止单个节点易丢失数据的可能性，也可以用来进行读写分离提高客户端操作性能。复制集中各节点的mongodb实例有相同的数据集副本。主节点可以接收客户端所有写操作记录到日志中，从库复制主库的操作日志记录应用到其数据库中。一个客户端只能有一个主节点，如果主节点不可用（10秒内无法连接），复制集中将选一个成员节点作为主节点。

mongodb主备+仲裁的基本结构如下：

下面简单介绍下MongoDB 副本集的部署过程：

1）服务器信息
sign-mongo01.wangshibo.cn  172.16.51.216   Primary
sign-mongo02.wangshibo.cn  172.16.51.217   Secondary
sign-mongo03.wangshibo.cn  172.16.51.218   Arbiter

三台服务器均设置好主机名，关闭iptables及selinux（略）

2）在3台服务器文件hosts文件中都添加以下3行：
[root@sign-mongo01 ~]# cat /etc/hosts
127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
172.16.51.216   sign-mongo01.wangshibo.cn
172.16.51.217   sign-mongo02.wangshibo.cn
172.16.51.218   sign-mongo03.wangshibo.cn 

3）安装部署mongodb（三台机器都安装）
下载地址：https://www.mongodb.org/dl/linux/x86_64-rhel62
[app@sign-mongo01 software]$ pwd
/data/software
[app@sign-mongo01 software]$ ls
mongodb-linux-x86_64-rhel62-v3.2-latest.tgz
[app@sign-mongo01 software]$ tar -zvxf mongodb-linux-x86_64-rhel62-v3.2-latest.tgz 
[app@sign-mongo01 software]$ mv mongodb-linux-x86_64-rhel62-3.2.17-34-g4c1bae566c /data/mongodb
[app@sign-mongo01 software]$ cd /data/mongodb/
[app@sign-mongo01 mongodb]$ mkdir data
[app@sign-mongo01 mongodb]$ mkdir log
[app@sign-mongo01 mongodb]$ vim mongodb.conf
pidfilepath=/data/mongodb/log/mongod.pid
logpath=/data/mongodb/log/mongod.log
dbpath=/data/mongodb
logappend=true
bind_ip=172.16.51.216
port=27017
fork=true
replSet=rs0

备节点的mongodb.conf配置文件分别为：
[app@sign-mongo02 mongodb]$ vim mongodb.conf
pidfilepath=/data/mongodb/log/mongod.pid
logpath=/data/mongodb/log/mongod.log
dbpath=/data/mongodb
logappend=true
bind_ip=172.16.51.217
port=27018
fork=true
replSet=rs0

其中：replSet=rs0  #表示复制集名称：rs0

启动主备服务器的mongodb
[app@sign-mongo01 ~]$ /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
about to fork child process, waiting until server is ready for connections.
forked process: 7317
child process started successfully, parent exiting
[app@sign-mongo01 mongodb]$ ps -ef|grep mongodb
app       7317     1  0 21:38 ?        00:00:00 /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
app       7342  7254  0 21:38 pts/1    00:00:00 grep mongodb
[app@sign-mongo01 mongodb]$ lsof -i:27017
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mongod  7317  app    6u  IPv4  27011      0t0  TCP sign-mongo01.wangshibo.cn:27017 (LISTEN)

[app@sign-mongo02 mongodb]$ /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
about to fork child process, waiting until server is ready for connections.
forked process: 9725
child process started successfully, parent exiting
[app@sign-mongo02 mongodb]$ lsof -i:27018
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mongod  9725  app    6u  IPv4  27191      0t0  TCP sign-mongo02.wangshibo.cn:27018 (LISTEN)

设置mongodb的环变量
[root@sign-mongo01 src]# vim /etc/profile
......
export PATH=$PATH:/data/mongodb/bin
[root@sign-mongo01 src]# source /etc/profile

登录到mongodb中：
[app@sign-mongo01 ~]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017/test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
    http://docs.mongodb.org/
Questions? Try the support group
    http://groups.google.com/group/mongodb-user
Server has startup warnings: 
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] 
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] 
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:38:18.063+0800 I CONTROL  [initandlisten] 
> 

初始化复制集：（集合为："rs0" ；第一个成员为："sign-mongo01.wangshibo.cn:27017" 
> rs.initiate({_id: "rs0",members: [{ _id: 0 , host: "sign-mongo01.wangshibo.cn:27017" }]})
{ "ok" : 1 }
rs0:OTHER>                    //接着回车，显示这个节点为Primary主节点
rs0:PRIMARY>

接着添加另1个成员：
rs0:PRIMARY> rs.add("sign-mongo02.wangshibo.cn:27018")
{ "ok" : 1 }

查看成员信息 （或者使用 db.isMaster() ）
rs0:PRIMARY> rs.status()
{
    "set" : "rs0",
    "date" : ISODate("2017-11-22T13:55:28.446Z"),
    "myState" : 1,
    "term" : NumberLong(1),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 1031,
            "optime" : {
                "ts" : Timestamp(1511358895, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2017-11-22T13:54:55Z"),
            "infoMessage" : "could not find member to sync from",
            "electionTime" : Timestamp(1511358843, 2),
            "electionDate" : ISODate("2017-11-22T13:54:03Z"),
            "configVersion" : 2,
            "self" : true
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 32,
            "optime" : {
                "ts" : Timestamp(1511358895, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2017-11-22T13:54:55Z"),
            "lastHeartbeat" : ISODate("2017-11-22T13:55:27.684Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-22T13:55:27.827Z"),
            "pingMs" : NumberLong(0),
            "configVersion" : 2
        }
    ],
    "ok" : 1
}


或者使用该方法查看，结果也是一样：
rs0:PRIMARY> use admin
switched to db admin
rs0:PRIMARY> db.runCommand( { replSetGetStatus : 1 } )  
{
    "set" : "rs0",
    "date" : ISODate("2017-11-23T01:12:20.701Z"),
    "myState" : 1,
    "term" : NumberLong(1),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 41643,
            "optime" : {
                "ts" : Timestamp(1511358895, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2017-11-22T13:54:55Z"),
            "electionTime" : Timestamp(1511358843, 2),
            "electionDate" : ISODate("2017-11-22T13:54:03Z"),
            "configVersion" : 2,
            "self" : true
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 40645,
            "optime" : {
                "ts" : Timestamp(1511358895, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2017-11-22T13:54:55Z"),
            "lastHeartbeat" : ISODate("2017-11-23T01:12:19.418Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T01:12:16.225Z"),
            "pingMs" : NumberLong(0),
            "configVersion" : 2
        }
    ],
    "ok" : 1
}
rs0:PRIMARY> 

详细说明如下：
"_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  

4）测试操作。在主库中，可以任意操作：
rs0:PRIMARY> show dbs
local  0.000GB
rs0:PRIMARY> use mydb      //切换到要创建的数据库
switched to db mydb
rs0:PRIMARY> show dbs      //use只是转到相关数据库，此时并没有做任何操作，所以并不会创建相应的数据库，只有当真正的操作了一次数据库就会自动创建。
local  0.000GB
rs0:PRIMARY> db.stats();
{
    "db" : "mydb",
    "collections" : 0,
    "objects" : 0,
    "avgObjSize" : 0,
    "dataSize" : 0,
    "storageSize" : 0,
    "numExtents" : 0,
    "indexes" : 0,
    "indexSize" : 0,
    "fileSize" : 0,
    "ok" : 1
}
rs0:PRIMARY> db.coll.insert({"id":1}) 
WriteResult({ "nInserted" : 1 })
rs0:PRIMARY> db.coll.find() 
{ "_id" : ObjectId("5a162222991b83743942d169"), "id" : 1 }
rs0:PRIMARY> db.coll.remove({"id":1}) 
WriteResult({ "nRemoved" : 1 })
rs0:PRIMARY> show dbs
local  0.000GB
mydb   0.000GB


现在到备库中
172.16.51.217 （sign-mongo02.wangshibo.cn ）
查看分库数据库目录，发现多了数据库，数据库与主库（172.16.51.216）一致！是主库同步过来的。
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018/test
Server has startup warnings: 
2017-11-22T21:46:38.417+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 

在副本服务器中登录其本地数据库，发现可以连接，但是无法读写操作：
rs0:SECONDARY> show dbs
2017-11-23T09:25:35.961+0800 E QUERY    [thread1] Error: listDatabases failed:{ "ok" : 0, "errmsg" : "not master and slaveOk=false", "code" : 13435 } :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
Mongo.prototype.getDBs@src/mongo/shell/mongo.js:62:1
shellHelper.show@src/mongo/shell/utils.js:781:19
shellHelper@src/mongo/shell/utils.js:671:15
@(shellhelp2):1:1
rs0:SECONDARY>

从库开启读操作（此时可以测试主库插入，从库查看，同步正常）：
rs0:SECONDARY> rs.slaveOk();  
rs0:SECONDARY> show dbs
local  0.000GB
mydb   0.000GB


5）现在模拟主库不可用，将主节点服务停止：
[app@sign-mongo01 mongodb]$ pkill -9 mongod
[app@sign-mongo01 mongodb]$ ps -ef|grep mongodb
app       9524  9398  0 09:32 pts/0    00:00:00 grep mongodb

到备节点172.16.51.217 中登录mongodb，查看复制集状态：
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018/test
Server has startup warnings: 
2017-11-22T21:46:38.417+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 
rs0:SECONDARY> rs.status() 
{
    "set" : "rs0",
    "date" : ISODate("2017-11-23T01:33:29.688Z"),
    "myState" : 2,
    "term" : NumberLong(1),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 0,
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : {
                "ts" : Timestamp(0, 0),
                "t" : NumberLong(-1)
            },
            "optimeDate" : ISODate("1970-01-01T00:00:00Z"),
            "lastHeartbeat" : ISODate("2017-11-23T01:33:28.732Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T01:32:28.099Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "Connection refused",
            "configVersion" : -1
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 42412,
            "optime" : {
                "ts" : Timestamp(1511399985, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2017-11-23T01:19:45Z"),
            "infoMessage" : "could not find member to sync from",
            "configVersion" : 2,
            "self" : true
        }
    ],
    "ok" : 1
}

有上面可看出，主节点删除服务进程，primary并没有切换到备节点上：
再次启动主节点的mongodb服务，发现primary才自动切换回到主节点：
[app@sign-mongo01 mongodb]$ nohup /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
nohup: ignoring input and appending output to `nohup.out'
[app@sign-mongo01 mongodb]$ ps -ef|grep mongodb
app       9538     1  8 09:37 ?        00:00:00 /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
app       9610  9398  0 09:37 pts/0    00:00:00 grep mongodb
[app@sign-mongo01 mongodb]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017/test
Server has startup warnings: 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
rs0:PRIMARY> rs.status()
{
    "set" : "rs0",
    "date" : ISODate("2017-11-23T01:38:19.631Z"),
    "myState" : 1,
    "term" : NumberLong(2),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 54,
            "optime" : {
                "ts" : Timestamp(1511401058, 2),
                "t" : NumberLong(2)
            },
            "optimeDate" : ISODate("2017-11-23T01:37:38Z"),
            "infoMessage" : "could not find member to sync from",
            "electionTime" : Timestamp(1511401058, 1),
            "electionDate" : ISODate("2017-11-23T01:37:38Z"),
            "configVersion" : 2,
            "self" : true
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 53,
            "optime" : {
                "ts" : Timestamp(1511401058, 2),
                "t" : NumberLong(2)
            },
            "optimeDate" : ISODate("2017-11-23T01:37:38Z"),
            "lastHeartbeat" : ISODate("2017-11-23T01:38:18.072Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T01:38:18.596Z"),
            "pingMs" : NumberLong(0),
            "syncingTo" : "sign-mongo01.wangshibo.cn:27017",
            "configVersion" : 2
        }
    ],
    "ok" : 1
}

+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
现在开始部署仲裁节点sign-mongo03.wangshibo.cn
[app@sign-mongo03 ~]$ mkdir /data/mongodb/arbiter
[app@sign-mongo03 ~]$ ll -d /data/mongodb/arbiter
drwxrwxr-x 2 app app 4096 Nov 23 09:39 /data/mongodb/arbiter

本案例是在普通用户app账号下部署的，权限都是app.app。
如果是在root账号下部署，那么需要将mongodb数据目录下的文件全部设置mongodb.mongodb权限

mongodb.conf配置：
[app@sign-mongo03 ~]$ vim /data/mongodb/mongodb.conf
pidfilepath=/data/mongodb/log/mongod.pid
logpath=/data/mongodb/log/mongod.log
dbpath=/data/mongodb/arbiter
logappend=false
bind_ip=172.16.51.218
port=27019
fork=true
replSet=rs0

接着重启服务：
[app@sign-mongo03 ~]$ /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
about to fork child process, waiting until server is ready for connections.
forked process: 9217
child process started successfully, parent exiting
[app@sign-mongo03 ~]$ ps -ef|grep mongo
app       9217     1  1 09:46 ?        00:00:00 /data/mongodb/bin/mongod --config /data/mongodb/mongodb.conf
app       9242  9158  0 09:46 pts/0    00:00:00 grep mongo
[app@sign-mongo03 ~]$ lsof -i:27019
COMMAND  PID USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
mongod  9217  app    6u  IPv4  37321      0t0  TCP sign-mongo03.wangshibo.cn:27019 (LISTEN)

然后在Paimary主节点sign-mongo01.wangshibo.cn的mongodb中添加仲裁节点并查看结果
[app@sign-mongo01 mongodb]$ mongo 172.16.51.216:27017
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.216:27017/test
Server has startup warnings: 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:37:26.467+0800 I CONTROL  [initandlisten] 
rs0:PRIMARY> rs.addArb("sign-mongo03.wangshibo.cn:27019")
{ "ok" : 1 }
rs0:PRIMARY> db.isMaster() 
{
    "hosts" : [
        "sign-mongo01.wangshibo.cn:27017",
        "sign-mongo02.wangshibo.cn:27018"
    ],
    "arbiters" : [
        "sign-mongo03.wangshibo.cn:27019"
    ],
    "setName" : "rs0",
    "setVersion" : 4,
    "ismaster" : true,
    "secondary" : false,
    "primary" : "sign-mongo01.wangshibo.cn:27017",
    "me" : "sign-mongo01.wangshibo.cn:27017",
    "electionId" : ObjectId("7fffffff0000000000000003"),
    "maxBsonObjectSize" : 16777216,
    "maxMessageSizeBytes" : 48000000,
    "maxWriteBatchSize" : 1000,
    "localTime" : ISODate("2017-11-23T01:59:03.554Z"),
    "maxWireVersion" : 4,
    "minWireVersion" : 0,
    "ok" : 1
}
rs0:PRIMARY> rs.status()
{
    "set" : "rs0",
    "date" : ISODate("2017-11-23T02:00:26.312Z"),
    "myState" : 1,
    "term" : NumberLong(3),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 368,
            "optime" : {
                "ts" : Timestamp(1511402420, 1),
                "t" : NumberLong(3)
            },
            "optimeDate" : ISODate("2017-11-23T02:00:20Z"),
            "electionTime" : Timestamp(1511402069, 1),
            "electionDate" : ISODate("2017-11-23T01:54:29Z"),
            "configVersion" : 5,
            "self" : true
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 367,
            "optime" : {
                "ts" : Timestamp(1511402420, 1),
                "t" : NumberLong(3)
            },
            "optimeDate" : ISODate("2017-11-23T02:00:20Z"),
            "lastHeartbeat" : ISODate("2017-11-23T02:00:26.306Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T02:00:26.309Z"),
            "pingMs" : NumberLong(0),
            "syncingTo" : "sign-mongo01.wangshibo.cn:27017",
            "configVersion" : 5
        },
        {
            "_id" : 3,
            "name" : "sign-mongo03.wangshibo.cn:27019",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",
            "uptime" : 93,
            "lastHeartbeat" : ISODate("2017-11-23T02:00:26.306Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T02:00:25.306Z"),
            "pingMs" : NumberLong(0),
            "configVersion" : 5
        }
    ],
    "ok" : 1
}


至此，添加完成！！
再次测试主备切换。关闭172.16.51.216（primary）中删除服务进程：
[app@sign-mongo01 mongodb]$ pkill -9 mongod
[app@sign-mongo01 mongodb]$ ps -ef|grep mongod
app       9664  9398  0 09:50 pts/0    00:00:00 grep mongod
[app@sign-mongo01 mongodb]$ lsof -i:27017
[app@sign-mongo01 mongodb]$ 

然后到172.16.51.217:27018（secondary）查看，发现primary已经切换为172.16.51.217
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.217:27018/test
Server has startup warnings: 
2017-11-22T21:46:38.417+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-22T21:46:38.418+0800 I CONTROL  [initandlisten] 
rs0:PRIMARY> rs.status()
{
    "set" : "rs0",
    "date" : ISODate("2017-11-23T02:01:17.762Z"),
    "myState" : 1,
    "term" : NumberLong(4),
    "heartbeatIntervalMillis" : NumberLong(2000),
    "members" : [
        {
            "_id" : 0,
            "name" : "sign-mongo01.wangshibo.cn:27017",
            "health" : 0,
            "state" : 8,
            "stateStr" : "(not reachable/healthy)",
            "uptime" : 0,
            "optime" : {
                "ts" : Timestamp(0, 0),
                "t" : NumberLong(-1)
            },
            "optimeDate" : ISODate("1970-01-01T00:00:00Z"),
            "lastHeartbeat" : ISODate("2017-11-23T02:01:17.316Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T02:01:04.327Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "Connection refused",
            "configVersion" : -1
        },
        {
            "_id" : 1,
            "name" : "sign-mongo02.wangshibo.cn:27018",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 44080,
            "optime" : {
                "ts" : Timestamp(1511402475, 2),
                "t" : NumberLong(4)
            },
            "optimeDate" : ISODate("2017-11-23T02:01:15Z"),
            "infoMessage" : "could not find member to sync from",
            "electionTime" : Timestamp(1511402475, 1),
            "electionDate" : ISODate("2017-11-23T02:01:15Z"),
            "configVersion" : 5,
            "self" : true
        },
        {
            "_id" : 3,
            "name" : "sign-mongo03.wangshibo.cn:27019",
            "health" : 1,
            "state" : 7,
            "stateStr" : "ARBITER",
            "uptime" : 145,
            "lastHeartbeat" : ISODate("2017-11-23T02:01:17.315Z"),
            "lastHeartbeatRecv" : ISODate("2017-11-23T02:01:15.316Z"),
            "pingMs" : NumberLong(0),
            "configVersion" : 5
        }
    ],
    "ok" : 1
}
rs0:PRIMARY> show dbs
local  0.000GB
mydb   0.000GB

有上面信息可知，添加仲裁节点后，primary能正常启动切换了！~

现在看看arbiter，连接到172.16.51.218:27019
[app@sign-mongo03 ~]$ mongo 172.16.51.218:27019
MongoDB shell version: 3.2.17-34-g4c1bae566c
connecting to: 172.16.51.218:27019/test
Welcome to the MongoDB shell.
For interactive help, type "help".
For more comprehensive documentation, see
    http://docs.mongodb.org/
Questions? Try the support group
    http://groups.google.com/group/mongodb-user
Server has startup warnings: 
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] 
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] 
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'
2017-11-23T09:58:34.978+0800 I CONTROL  [initandlisten] 
rs0:ARBITER> rs.slaveOk(); 
rs0:ARBITER> db.isMaster()
{
    "hosts" : [
        "sign-mongo01.wangshibo.cn:27017",
        "sign-mongo02.wangshibo.cn:27018"
    ],
    "arbiters" : [
        "sign-mongo03.wangshibo.cn:27019"
    ],
    "setName" : "rs0",
    "setVersion" : 5,
    "ismaster" : false,
    "secondary" : false,
    "primary" : "sign-mongo02.wangshibo.cn:27018",
    "arbiterOnly" : true,
    "me" : "sign-mongo03.wangshibo.cn:27019",
    "maxBsonObjectSize" : 16777216,
    "maxMessageSizeBytes" : 48000000,
    "maxWriteBatchSize" : 1000,
    "localTime" : ISODate("2017-11-23T02:03:33.874Z"),
    "maxWireVersion" : 4,
    "minWireVersion" : 0,
    "ok" : 1
}
rs0:ARBITER> show dbs
local  0.000GB

arbiter 最为仲裁者，没有数据副本存储在本地，能读取复制集的信息。
-------------------------------------------------------------------------------------------------
在primary主库上，创建locs数据库，该库的用户名为locsopr，密码为locsopr@123
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018
......
rs0:PRIMARY> use locs
switched to db locs
rs0:PRIMARY> db.createUser({user:"locsopr",pwd :"locsopr@123",roles:["readWrite"]})
Successfully added user: { "user" : "locsopr", "roles" : [ "readWrite" ] }
rs0:PRIMARY> show users;          //查看当前库下的用户名
{
    "_id" : "locs.locsopr",
    "user" : "locsopr",
    "db" : "locs",
    "roles" : [
        {
            "role" : "readWrite",
            "db" : "locs"
        }
    ]
}


使用上面的用户登录primary主库
[app@sign-mongo02 ~]$ mongo 172.16.51.217:27018/locs -ulocsopr -plocsopr@123
.........
rs0:PRIMARY> show users
{
    "_id" : "locs.locsopr",
    "user" : "locsopr",
    "db" : "locs",
    "roles" : [
        {
            "role" : "readWrite",
            "db" : "locs"
        }
    ]
}
rs0:PRIMARY> show dbs
admin  0.000GB
local  0.000GB
rs0:PRIMARY> 

再登录从库看下：
[app@sign-mongo01 ~]$ mongo 172.16.51.216:27017/locs -ulocsopr -plocsopr@123
.......
rs0:SECONDARY> rs.slaveOk();
rs0:SECONDARY> show users
{
    "_id" : "locs.locsopr",
    "user" : "locsopr",
    "db" : "locs",
    "roles" : [
        {
            "role" : "readWrite",
            "db" : "locs"
        }
    ]
}
rs0:SECONDARY> show dbs
admin  0.000GB
local  0.000GB

------------------------------------------------------------------------------------------------------------------------------------------------------- 上面介绍的是三台mongodb节点：一主一备一仲裁，这样，主节点挂了后，通过仲裁机制将primary自动切换到备机上！如果上面的三台mongodb节点：一主两备，没有仲裁节点，那么主节点挂了后，primary会自动切换到其余两台备节点中的一台上！

一主两从（端口分别为27017、27018、27019）的mongodb配置和上面一主一从（端口分别为27017、27018）的配置一样。
多加的一个从节点，在主节点登陆mongodb，使用rs.add命令将这个成员加到集群中即可！

一主两从的模式，比如：
主节点sign-mongo01.wangshibo.cn的mongodb服务程序挂了后，另外两个从节点中的一个（比如sign-mongo02.wangshibo.cn）会自动变成primary主节点，
另一个节点sign-mongo03.wangshibo.cn则是新的主节点（sign-mongo02.wangshibo.cn）的从节点。

++++++++++++++++++++++++++++++如果想让切换回原来的主节点，做法如下+++++++++++++++++++++++++++++++
1）恢复原来的主节点sign-mongo01.wangshibo.cn的mongodb服务，使用命令rs.status() 确认数据集成员运行正常。
2）到次节点sign-mongo03.wangshibo.cn中登录mongodb，运行freeze使其120内不会变为主节点。  
> rs.freeze(120)  
3) 到新的主节点sign-mongo02.wangshibo.cn中强制切换主节点，stepDown将阻止长事务和写入操作  
> rs.stepDown(120) 
4）此时sign-mongo01.wangshibo.cn节点变成primary主节点。使用rs.status()命令可以查看到集群状态。

+++++++++++++++++++++++若要使某个节点永远不会变为主节点，设置优先级为0即可+++++++++++++++++++++++
登陆当前主节点的mongodb，执行下面操作：
rs0:PRIMARY> cfg = rs.conf()  
rs0:PRIMARY> cfg.members[0].priority = 0.5  
rs0:PRIMARY> cfg.members[1].priority = 0.5  
rs0:PRIMARY> cfg.members[2].priority = 0  
rs0:PRIMARY> rs.reconfig(cfg)  

说明：
其中成员编号0/1/2为 rs.status()中的 "_id"值  
members[2]表示sign-mongo03.wangshibo.cn，则它将永远不会变成主节点！因为优先级设置为0了！

++++++++++++++++++++++++++++++++移除一个复制成员（两种方法）++++++++++++++++++++++++++++++++++++
登陆当前主节点的mongodb，执行下面操作：
rs0:PRIMARY> rs.remove("sign-mongo03.wangshibo.cn:27019")  
rs0:PRIMARY> rs.conf()  

或者：  
rs0:PRIMARY> cfg = rs.conf()  
rs0:PRIMARY> cfg.members.splice(2,1)  
rs0:PRIMARY> rs.reconfig(cfg)  

移除后到移除的节点服务器（即sign-mongo03.wangshibo.cn），更改配置文件mongod.conf
#replSet=rs0       //将这一行注释
然后再重启mongodb服务，这就完成了移除（数据库文件仍保留在当前服务器）。

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原始发表：2017-11-22 ，如有侵权请联系 cloudcommunity@tencent.com 删除

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