MongoDB复制是将数据同步在多个服务器的过程。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。
复制还允许您从硬件故障和服务中断中恢复数据。
创建副本集时注意
- 版本: 各副本集服务器的MongoDB版本一致或支持同样的replSet功能
- 网络: 副本集内的每个成员都必须能够连接到其他成员(包括自身),启动时注意bind_ip --bind_ip_all.
配置副本集
- 1 建立配置文件
mongodb.conf
1 # Start MongoDB as a daemon on port 27017
2
3 port = 27017
4 fork = true
5 replSet = test_replica_set
6 dbpath = /datatest/db
7 logpath = /datatest/db/test.log
8 logappend = true
9
mongodb2.conf
2
3 port = 27017
4 fork = true
5 replSet = test_replica_set
6 dbpath = /datatest/db
7 logpath = /datatest/db/test.log
8 logappend = true
9
mongodb3.conf
2
3 port = 27017
4 fork = true
5 replSet = test_replica_set
6 dbpath = /datatest/db
7 logpath = /datatest/db/test.log
8 logappend = true
9
- 2 启动数据库
mac-abeen:bin abeen$ sudo ./mongod -f mongodb.conf
about to fork child process, waiting until server is ready for connections.
forked process: 37181
child process started successfully, parent exiting
mac-abeen:bin abeen$ sudo ./mongod -f mongodb2.conf
about to fork child process, waiting until server is ready for connections.
forked process: 37185
child process started successfully, parent exiting
mac-abeen:bin abeen$ sudo ./mongod -f mongodb3.conf
about to fork child process, waiting until server is ready for connections.
forked process: 37189
child process started successfully, parent exiting
- 3 初始化副本集
mac-abeen:bin abeen$ ./mongo --nodb
MongoDB shell version: 3.2.8
> config = {}
{ }
> config = {"_id": "test_replica_set", "members": [
{"_id": 0, "host": "192.168.0.10:27017"},
{"_id": 1, "host": "192.168.0.20:27017"},
{"_id": 2, "host": "192.168.0.30:27017"}]}
{
"_id" : "test_replica_set",
"members" : [
{
"_id" : 0,
"host" : "192.168.0.10:27017"
},
{
"_id" : 1,
"host" : "192.168.0.20:27017"
},
{
"_id" : 2,
"host" : "192.168.0.30:27017"
}
]
}
> db = (new Mongo("192.168.0.10:27017")).getDB("test")
test
> rs.initiate(config)
{ "ok" : 1 }
test_replica_set:OTHER>
test_replica_set:PRIMARY> rs.config()
{
"_id" : "test_replica_set",
"version" : 1,
"protocolVersion" : NumberLong(1),
"members" : [
{
"_id" : 0,
"host" : "192.168.0.10:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "192.168.0.20:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "192.168.0.30:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatIntervalMillis" : 2000,
"heartbeatTimeoutSecs" : 10,
"electionTimeoutMillis" : 10000,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicaSetId" : ObjectId("5850f445c8cacd70496883b0")
}
}
- 4 写入数据并查看副本集数据
test_replica_set:PRIMARY>
test_replica_set:PRIMARY> for (i=0; i < 100; i++){db.coll.insert({"count": i})}
WriteResult({ "nInserted" : 1 })
test_replica_set:PRIMARY> db.coll.count()
100
test_replica_set:PRIMARY> db.coll.find().limit(5)
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b51"), "count" : 0 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b52"), "count" : 1 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b53"), "count" : 2 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b54"), "count" : 3 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b55"), "count" : 4 }
- 5 查看副本集是否有数据
mac-abeen:bin abeen$ ./mongo --port 27017 --host 192.168.0.20
MongoDB shell version: 3.2.8
connecting to: 192.168.0.20:27017/test
test_replica_set:SECONDARY> db.coll.find().limit(5)
Error: error: { "ok" : 0, "errmsg" : "not master and slaveOk=false", "code" : 13435 }
设置连接可读取数据
test_replica_set:SECONDARY> db.setSlaveOk()
副本中已有数据
test_replica_set:SECONDARY> db.coll.find().limit(5)
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b53"), "count" : 2 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b55"), "count" : 4 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b52"), "count" : 1 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b54"), "count" : 3 }
{ "_id" : ObjectId("5850f5f35f1a7d82c0b45b51"), "count" : 0 }
修改副本集
rs.add("server-4:27017") //添加
rs.addArb("server-4:27017") //添加选举仲裁者
rs.add({"_id": 4, "host": "server-4:27017", "arbiterOnly": true) //添加选举仲裁者
rs.add({"_id": 5, "host": "server-5:27017", "priority": 0, "hidden": true) //添加隐藏成员
rs.remove("server-4:27017") //移除
修改副本集,通过rs.reconfig
rs.reconfig修改副本集成员时限制
- 不能修改成员的_id 字段
- 不能将接收rs.reconfig命令的成员(通常是主节点)的优先级设为0
- 不能仲裁者成员变为非仲裁者成员,反之亦然.
- 不能将buildIndexes: false的成员修改为buildIndexes: true
可以修改其他,比如host
var config = rs.config()
config.members[1].host = "newsserver:27017" //修改host
rs.reconfig(config)
更多MongoDB相关教程见以下内容：