MongoDB Replica Set 副本集

1、简介

MongoDB复制是将数据同步在多个服务器的过程，类似MySQL Replication是一种异步复制；

复制提供了数据的冗余备份，并在多个服务器上存储数据副本，提高了数据的可用性， 并可以保证数据的安全性。

2、MongoDB复制特点

(1) mongodb的节点有三种角色：primary,seconfary,arbiter, 

primary负责处理客户端请求，读写数据；

secondary通过oplog复制主节点上的数据,也可读数据; 

arbiter节点不存储数据，仅投票功能，所以不需要单独的硬件配置；

(2)如果primary不可以用，secondary会提升为新的primary; 由参数electionTimeoutMillis=10s控制

3、实验环境

MongoDB-3.0.6版本

一台物理机器上三个MongoDB实例，分别占用三个节点

172.16.101.54  27017

172.16.101.54  27018

172.16.101.54  27019

4、创建数据和日志目录

[root@sht-sgmhadoopcm-01 mongodb]# mkdir -p /usr/local/mongodb/data/{db27017,db27018,db27019}

[root@sht-sgmhadoopcm-01 mongodb]# mkdir -p /usr/local/mongodb/log

5、配置文件/etc/mongod.conf

三个节点分别创建配置文件，文件内容区别是节点不同,其他都相同，参数replSetname用来指定副本集名称为rs0

[root@sht-sgmhadoopcm-01 mongodb]# ll /etc/mongod2701*.conf

-rw-r--r-- 1 root root 405 Nov  2 20:21 /etc/mongod27017.conf

-rw-r--r-- 1 root root 405 Nov  2 20:13 /etc/mongod27018.conf

-rw-r--r-- 1 root root 405 Nov  2 20:13 /etc/mongod27019.conf

mongodb配置文件每个冒号后面要有一个空格，否则会报错

[root@sht-sgmhadoopcm-01 mongodb]# cat /etc/mongod27017.conf systemLog:    destination: file    path: "/usr/local/mongodb/log/mongod27017.log"    logAppend: true storage:    dbPath: /usr/local/mongodb/data/db27017    journal:       enabled: true processManagement:    fork: true    pidFilePath: /usr/local/mongodb/data/db27017/mongod27017.pid net:    port: 27017    bindIp: 0.0.0.0 setParameter:    enableLocalhostAuthBypass: false replication:   replSetName: rs0

6、启动MongoDB

分别启动三个节点的MongoDB服务，并指定配置文件

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27017.conf

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27018.conf 

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27019.conf 

7、初始化副本集

登录27017节点

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo  172.16.101.54:27017/admin

> rs.initiate()

{

    "info2" : "no configuration explicitly specified -- making one",

    "me" : "sht-sgmhadoopcm-01:27017",

    "ok" : 1

}

添加成员到副本集，priority大的节点提成为主的可能性就大

rs0:PRIMARY> rs.add('172.16.101.54:27018')

{ "ok" : 1 }

rs0:PRIMARY> rs.add('172.16.101.54:27019',priority:5)

{ "ok" : 1 }

查看副本集配置

rs0:PRIMARY> rs.conf() {     "_id" : "rs0",     "version" : 3,     "members" : [         {             "_id" : 0,             "host" : "sht-sgmhadoopcm-01:27017",             "arbiterOnly" : false,             "buildIndexes" : true,             "hidden" : false,             "priority" : 1,             "tags" : {                              },             "slaveDelay" : 0,             "votes" : 1         },         {             "_id" : 1,             "host" : "172.16.101.54:27018",             "arbiterOnly" : false,             "buildIndexes" : true,             "hidden" : false,             "priority" : 1,             "tags" : {                              },             "slaveDelay" : 0,             "votes" : 1         },         {             "_id" : 2,             "host" : "172.16.101.54:27019",             "arbiterOnly" : false,             "buildIndexes" : true,             "hidden" : false,             "priority" : 1,             "tags" : {                              },             "slaveDelay" : 0,             "votes" : 1         }     ],     "settings" : {         "chainingAllowed" : true,         "heartbeatTimeoutSecs" : 10,         "getLastErrorModes" : {                      },         "getLastErrorDefaults" : {             "w" : 1,             "wtimeout" : 0         }     } }

查看各个角色状态

rs0:PRIMARY> rs.status() {     "set" : "rs0",     "date" : ISODate("2018-11-02T12:27:44.570Z"),     "myState" : 1,     "members" : [         {             "_id" : 0,             "name" : "sht-sgmhadoopcm-01:27017",             "health" : 1,             "state" : 1,             "stateStr" : "PRIMARY",             "uptime" : 626,             "optime" : Timestamp(1541161589, 1),             "optimeDate" : ISODate("2018-11-02T12:26:29Z"),             "electionTime" : Timestamp(1541161465, 2),             "electionDate" : ISODate("2018-11-02T12:24:25Z"),             "configVersion" : 3,             "self" : true         },         {             "_id" : 1,             "name" : "172.16.101.54:27018",             "health" : 1,             "state" : 2,             "stateStr" : "SECONDARY",             "uptime" : 161,             "optime" : Timestamp(1541161589, 1),             "optimeDate" : ISODate("2018-11-02T12:26:29Z"),             "lastHeartbeat" : ISODate("2018-11-02T12:27:43.430Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T12:27:43.311Z"),             "pingMs" : 0,             "syncingTo" : "sht-sgmhadoopcm-01:27017",             "configVersion" : 3         },         {             "_id" : 2,             "name" : "172.16.101.54:27019",             "health" : 1,             "state" : 2,             "stateStr" : "SECONDARY",             "uptime" : 75,             "optime" : Timestamp(1541161589, 1),             "optimeDate" : ISODate("2018-11-02T12:26:29Z"),             "lastHeartbeat" : ISODate("2018-11-02T12:27:43.430Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T12:27:43.430Z"),             "pingMs" : 0,             "lastHeartbeatMessage" : "could not find member to sync from",             "configVersion" : 3         }     ],     "ok" : 1 }

8、数据同步测试

向27017节点插入数据

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo 172.16.101.54:27017/admin

rs0:PRIMARY> db.user.insert({"username":"test","age":12,"sex":"m"})

WriteResult({ "nInserted" : 1 })

rs0:PRIMARY> db.user.find()

{ "_id" : ObjectId("5bdc65ff048de313da6c425a"), "username" : "test", "age" : 12, "sex" : "m" }

数据成功的同步到27018和27019节点

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo  172.16.101.54:27018/admin

rs0:SECONDARY> db.getMongo().setReadPref('secondaryPreferred')

rs0:SECONDARY> db.user.find()

{ "_id" : ObjectId("5bdc65ff048de313da6c425a"), "username" : "test", "age" : 12, "sex" : "m" }

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo  172.16.101.54:27019/admin

rs0:SECONDARY> db.getMongo().setReadPref('secondaryPreferred')

rs0:SECONDARY> db.user.find()

{ "_id" : ObjectId("5bdc65ff048de313da6c425a"), "username" : "test", "age" : 12, "sex" : "m" }

9、AutoFailover测试

kill当前的primary27017节点

[root@sht-sgmhadoopcm-01 mongodb]# ps -ef|grep mongod

root      5703     1  0 20:17 ?        00:00:52 bin/mongod --config /etc/mongod27017.conf

root      5747     1  0 20:17 ?        00:00:51 bin/mongod --config /etc/mongod27018.conf

root      5979     1  0 20:20 ?        00:00:52 bin/mongod --config /etc/mongod27019.conf

[root@sht-sgmhadoopcm-01 mongodb]# kill -9 5703

可以看到27019变成primary,此时27017不可用

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongo  172.16.101.54:27018/admin

rs0:SECONDARY> rs.status() {     "set" : "rs0",     "date" : ISODate("2018-11-02T15:10:18.746Z"),     "myState" : 2,     "members" : [         {             "_id" : 0,             "name" : "sht-sgmhadoopcm-01:27017",             "health" : 0,             "state" : 8,             "stateStr" : "(not reachable/healthy)",             "uptime" : 0,             "optime" : Timestamp(0, 0),             "optimeDate" : ISODate("1970-01-01T00:00:00Z"),             "lastHeartbeat" : ISODate("2018-11-02T15:10:18.631Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T15:09:28.583Z"),             "pingMs" : 0,             "lastHeartbeatMessage" : "Failed attempt to connect to sht-sgmhadoopcm-01:27017; couldn't connect to server sht-sgmhadoopcm-01:27017 (172.16.101.54), connection attempt failed",             "configVersion" : -1         },         {             "_id" : 1,             "name" : "172.16.101.54:27018",             "health" : 1,             "state" : 2,             "stateStr" : "SECONDARY",             "uptime" : 10349,             "optime" : Timestamp(1541170688, 2),             "optimeDate" : ISODate("2018-11-02T14:58:08Z"),             "configVersion" : 3,             "self" : true         },         {             "_id" : 2,             "name" : "172.16.101.54:27019",             "health" : 1,             "state" : 1,             "stateStr" : "PRIMARY",             "uptime" : 9827,             "optime" : Timestamp(1541170688, 2),             "optimeDate" : ISODate("2018-11-02T14:58:08Z"),             "lastHeartbeat" : ISODate("2018-11-02T15:10:18.611Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T15:10:18.592Z"),             "pingMs" : 0,             "electionTime" : Timestamp(1541171370, 1),             "electionDate" : ISODate("2018-11-02T15:09:30Z"),             "configVersion" : 3         }     ],     "ok" : 1 }

重新启动27017节点，会自动变成了27019的备库，说明auto failover成功了

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27017.conf

rs0:PRIMARY> rs.status() {     "set" : "rs0",     "date" : ISODate("2018-11-02T15:13:27.035Z"),     "myState" : 1,     "members" : [         {             "_id" : 0,             "name" : "sht-sgmhadoopcm-01:27017",             "health" : 1,             "state" : 2,             "stateStr" : "SECONDARY",             "uptime" : 42,             "optime" : Timestamp(1541170688, 2),             "optimeDate" : ISODate("2018-11-02T14:58:08Z"),             "lastHeartbeat" : ISODate("2018-11-02T15:13:26.764Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T15:13:25.055Z"),             "pingMs" : 0,             "configVersion" : 3         },         {             "_id" : 1,             "name" : "172.16.101.54:27018",             "health" : 1,             "state" : 2,             "stateStr" : "SECONDARY",             "uptime" : 10017,             "optime" : Timestamp(1541170688, 2),             "optimeDate" : ISODate("2018-11-02T14:58:08Z"),             "lastHeartbeat" : ISODate("2018-11-02T15:13:26.662Z"),             "lastHeartbeatRecv" : ISODate("2018-11-02T15:13:26.678Z"),             "pingMs" : 0,             "lastHeartbeatMessage" : "could not find member to sync from",             "configVersion" : 3         },         {             "_id" : 2,             "name" : "172.16.101.54:27019",             "health" : 1,             "state" : 1,             "stateStr" : "PRIMARY",             "uptime" : 10349,             "optime" : Timestamp(1541170688, 2),             "optimeDate" : ISODate("2018-11-02T14:58:08Z"),             "electionTime" : Timestamp(1541171370, 1),             "electionDate" : ISODate("2018-11-02T15:09:30Z"),             "configVersion" : 3,             "self" : true         }     ],     "ok" : 1 }

FAQ

[root@sht-sgmhadoopcm-01 mongodb]# bin/mongod --config /etc/mongod27017.conf &

[1] 4885

[root@sht-sgmhadoopcm-01 mongodb]# Error parsing YAML config file: yaml-cpp: error at line 8, column 11: illegal map value

try 'bin/mongod --help' for more information

[1]+  Exit 2                  bin/mongod --config /etc/mongod27017.conf

原因是配置文件/etc/mongod.conf冒号后面没有跟空格。

参考链接

MongoDB Replication