说明：该篇内容部分来自红丸编写的MongoDB实战文章。
1、简介
MongoDB支持在多个机器中通过异步复制达到故障转移和实现冗余，多机器中同一时刻只有一台是用于写操作，正是由于这个情况，为了MongoDB提供了数据一致性的保障，担当primary角色的服务能把读操作分发给Slave(详情请看前两篇关于Replica Set成员组成和理解)。
MongoDB高可用分为两种：
IMPORTANT
Replica sets replace master-slave replication for most use cases. If possible, use replica sets rather than master-slave replication for all new production deployments. This documentation remains to support legacy deployments and for archival purposes only.
意思就是说在很多的案例中已经用Replica Set来替代Master-slave。
[root@localhost mongodb]# mkdir -p r0 [root@localhost mongodb]# mkdir -p r1 [root@localhost mongodb]# mkdir -p r2创建日志文件路径：
[root@localhost mongodb]# mkdir -p log创建主从key文件，用于标识集群的私钥的完整路径，如果各个实例的keyfile内容不一致，程序将不能正常启动。
[root@localhost mongodb]# mkdir -p key
[root@localhost mongodb]# echo "this is rs1 super secret key">key/r0 [root@localhost mongodb]# echo "this is rs1 super secret key">key/r1 [root@localhost mongodb]# echo "this is rs1 super secret key">key/r2 [root@localhost mongodb]# chmod 600 key/r* [root@localhost mongodb]#启动三个实例：
[root@localhost bin]# ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r0 --fork --port 28010 --dbpath=/usr/local/mongodb/r0 --logpath=/usr/local/mongodb/log/r0.log --logappend about to fork child process, waiting until server is ready for connections. forked process: 2545
[root@localhost bin]# ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r1 --fork --port 28011 --dbpath=/usr/local/mongodb/r1 --logpath=/usr/local/mongodb/log/r1.log --logappend about to fork child process, waiting until server is ready for connections. forked process: 2596
[root@localhost bin]# ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r2 --fork --port 28012 --dbpath=/usr/local/mongodb/r2 --logpath=/usr/local/mongodb/log/r2.log --logappend about to fork child process, waiting until server is ready for connections. forked process: 2602说明：三个实例端口分别为28010、28011、28012 数据存放文件分别为r0、r1、r2。
[root@localhost bin]# ./mongo --port 28010
MongoDB shell version: 2.6.6
connecting to: 127.0.0.1:28010/test
> config_rs1={_id:"rs1",members:[{_id:0,host:'localhost:28010',priority:1},{_id:1,host:'localhost:28011'},{_id:2,host:'localhost:28012'}]}
{
"_id" : "rs1",
"members" : [
{
"_id" : 0,
"host" : "localhost:28010",
"priority" : 1
},
{
"_id" : 1,
"host" : "localhost:28011"
},
{
"_id" : 2,
"host" : "localhost:28012"
}
]
}
> 说明：指定每个阶段的IP和端口，priority=1作用将端口28010设置为primary。> rs.initiate(config_rs1);
{
"info" : "Config now saved locally. Should come online in about a minute.",
"ok" : 1
}
>
查看复制集的状态：rs1:OTHER> rs.status();
{
"set" : "rs1",
"date" : ISODate("2015-01-16T03:10:41Z"),
"myState" : 2,
"members" : [
{
"_id" : 0,
"name" : "localhost:28010",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 260,
"optime" : Timestamp(1421377833, 1),
"optimeDate" : ISODate("2015-01-16T03:10:33Z"),
"self" : true
},
{
"_id" : 1,
"name" : "localhost:28011",
"health" : 1,
<span style="background-color: rgb(255, 0, 0);"><span style="color:#ff0000;"> </span>"state" : 5,
"stateStr" : "STARTUP2",</span>
"uptime" : 8,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:10:39Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:10:39Z"),
"pingMs" : 0,
"<span style="background-color: rgb(255, 0, 0);">lastHeartbeatMessage" : "initial sync need a member to be primary or secondary to do our initial sync"</span>
},
{
"_id" : 2,
"name" : "localhost:28012",
"health" : 1,
"state" : 5,
"stateStr" : "STARTUP2",
"uptime" : 8,
"optime" : Timestamp(0, 0),
"optimeDate" : ISODate("1970-01-01T00:00:00Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:10:39Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:10:40Z"),
"pingMs" : 0,
<span style="background-color: rgb(255, 0, 0);">"lastHeartbeatMessage" : "initial sync need a member to be primary or secondary to do our initial sync"</span>
}
],
"ok" : 1
}rs1:PRIMARY> rs.status();
{
"set" : "rs1",
"date" : ISODate("2015-01-16T03:13:09Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "localhost:28010",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 408,
"optime" : Timestamp(1421377833, 1),
"optimeDate" : ISODate("2015-01-16T03:10:33Z"),
"electionTime" : Timestamp(1421377841, 1),
"electionDate" : ISODate("2015-01-16T03:10:41Z"),
"self" : true
},
{
"_id" : 1,
"name" : "localhost:28011",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 156,
"optime" : Timestamp(1421377833, 1),
"optimeDate" : ISODate("2015-01-16T03:10:33Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:13:09Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:13:07Z"),
"pingMs" : 1,
"syncingTo" : "localhost:28010"
},
{
"_id" : 2,
"name" : "localhost:28012",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 156,
"optime" : Timestamp(1421377833, 1),
"optimeDate" : ISODate("2015-01-16T03:10:33Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:13:08Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:13:09Z"),
"pingMs" : 0,
"syncingTo" : "localhost:28010"
}
],
"ok" : 1
}此时Replica Set已经初始化完成，各个节点状态均以正常，state=1的为primary服务。state=2的为SECONDARY服务节点。两个SECONDARY状态的阶段都是通过28010端口同步数据，通过syncingTo字段可以看出。rs1:PRIMARY> rs.isMaster();
{
"setName" : "rs1",
"setVersion" : 1,
"ismaster" : true,
"secondary" : false,
"hosts" : [
"localhost:28010",
"localhost:28012",
"localhost:28011"
],
"primary" : "localhost:28010",
"me" : "localhost:28010",
"maxBsonObjectSize" : 16777216,
"maxMessageSizeBytes" : 48000000,
"maxWriteBatchSize" : 1000,
"localTime" : ISODate("2015-01-16T02:38:58.479Z"),
"maxWireVersion" : 2,
"minWireVersion" : 0,
"ok" : 1
}
rs1:PRIMARY> rs1:PRIMARY> use local switched to db local rs1:PRIMARY> show collections me oplog.rs startup_log system.indexes system.replset rs1:PRIMARY> \
rs1:PRIMARY> db.oplog.rs.find();
{ "ts" : Timestamp(1421375729, 1), "h" : NumberLong(0), "v" : 2, "op" : "n", "ns" : "", "o" : { "msg" : "initiating set" } }
rs1:PRIMARY> rs1:PRIMARY> db.printReplicationInfo(); configured oplog size: 990MB log length start to end: 0secs (0hrs) oplog first event time: Fri Jan 16 2015 10:35:29 GMT+0800 (CST) oplog last event time: Fri Jan 16 2015 10:35:29 GMT+0800 (CST) now: Fri Jan 16 2015 10:45:18 GMT+0800 (CST) rs1:PRIMARY>字段说明：
rs1:PRIMARY> db.printSlaveReplicationInfo();
source: localhost:28011
syncedTo: Thu Jan 01 1970 08:00:00 GMT+0800 (CST)
1421375729 secs (394826.59 hrs) behind the primary
source: localhost:28012
syncedTo: Thu Jan 01 1970 08:00:00 GMT+0800 (CST)
1421375729 secs (394826.59 hrs) behind the primary
rs1:PRIMARY> 字段说明：rs1:PRIMARY> db.system.replset.find();
{ "_id" : "rs1", "version" : 1, "members" : [ { "_id" : 0, "host" : "localhost:28010" }, { "_id" : 1, "host" : "localhost:28011" }, { "_id" : 2, "host" : "localhost:28012" } ] }
rs1:PRIMARY>
从这个集合中可以看出，Replica Sets的配置信息，也可以在任何一个成员实例上执行rs.conf()来查看配置信息。[root@localhost bin]# ./mongo --port 28010
MongoDB shell version: 2.6.6
connecting to: 127.0.0.1:28010/test
rs1:PRIMARY> db.student.insert({name:"zhangsan",age:20});
WriteResult({ "nInserted" : 1 })
<span style="background-color: rgb(255, 0, 0);">rs1:PRIMARY</span>> db.student.find();
{ "_id" : ObjectId("54b87ca7f663c819d621d590"), "name" : "zhangsan", "age" : 20 }
rs1:PRIMARY>
[root@localhost bin]# ./mongo --port 28011
MongoDB shell version: 2.6.6
connecting to: 127.0.0.1:28011/test
rs1:SECONDARY> show collections
2015-01-16T11:22:54.517+0800 error: { "$err" : "<span style="background-color: rgb(255, 102, 102);">not master and slaveOk=false</span>", "code" : 13435 } at src/mongo/shell/query.js:131rs1:SECONDARY> db.getMongo().setSlaveOk();
<span style="background-color: rgb(255, 0, 0);">rs1:SECONDARY</span>> show collections; student system.indexes rs1:SECONDARY>此时便可以进行查询操作了。
rs1:SECONDARY> db.student.find();
{ "_id" : ObjectId("54b883fb7bd891605d9c300f"), "name" : "zhangsan", "age" : 20 }
rs1:SECONDARY> 28012端口操作如下：[root@localhost bin]# ./mongo --port 28012
MongoDB shell version: 2.6.6
connecting to: 127.0.0.1:28012/test
rs1:SECONDARY> show collections
2015-01-16T11:27:04.747+0800 error: { "$err" : "not master and slaveOk=false", "code" : 13435 } at src/mongo/shell/query.js:131
rs1:SECONDARY> db.getMongo().setSlaveOk();
rs1:SECONDARY> show collections
student
system.indexes
rs1:SECONDARY> db.student.find();
{ "_id" : ObjectId("54b883fb7bd891605d9c300f"), "name" : "zhangsan", "age" : 20 }
rs1:SECONDARY> 在28011端口上进行写操作：[root@localhost bin]# ./mongo --port 28011
MongoDB shell version: 2.6.6
connecting to: 127.0.0.1:28011/test
rs1:SECONDARY> db.student.insert({name:"lisi",age:20});
WriteResult({ "writeError" : { "code" : undefined, "errmsg" : "not master" } })此时提示不是master不能进行写操作，这跟前面两章节详细讲解Replica Set架构的相关原理相符合。bye [root@localhost bin]# <span style="color:#ff0000;">ps aux|grep mongod</span> root <span style="background-color: rgb(255, 0, 0);"> 6658 </span> 0.8 3.7 3175956 37508 ? Sl 11:06 0:12 ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r0 --fork --port <span style="background-color: rgb(255, 0, 0);">28010</span> --dbpath=/usr/local/mongodb/r0 --logpath=/usr/local/mongodb/log/r0.log --logappend root 7461 0.7 3.7 3144172 37764 ? Sl 11:06 0:11 ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r1 --fork --port 28011 --dbpath=/usr/local/mongodb/r1 --logpath=/usr/local/mongodb/log/r1.log --logappend root 28166 0.6 3.8 3144152 38520 ? Sl 11:10 0:08 ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r2 --fork --port 28012 --dbpath=/usr/local/mongodb/r2 --logpath=/usr/local/mongodb/log/r2.log --logappend root 30833 0.0 0.0 103244 832 pts/1 S+ 11:31 0:00 grep mongod [root@localhost bin]# <span style="background-color: rgb(255, 0, 0);">kill -2 6658</span> [root@localhost bin]# ps aux|grep mongod root 7461 0.7 3.7 3158520 37960 ? Sl 11:06 0:11 ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r1 --fork --port 28011 --dbpath=/usr/local/mongodb/r1 --logpath=/usr/local/mongodb/log/r1.log --logappend root 28166 0.6 3.8 3154396 38616 ? Sl 11:10 0:08 ./mongod --replSet rs1 --keyFile=/usr/local/mongodb/key/r2 --fork --port 28012 --dbpath=/usr/local/mongodb/r2 --logpath=/usr/local/mongodb/log/r2.log --logappend root 30869 0.0 0.0 103244 832 pts/1 S+ 11:31 0:00 grep mongod [root@localhost bin]#此时通过28011端口连接mongod服务并查看复制集状态
rs1:PRIMARY> rs.status()
{
"set" : "rs1",
"date" : ISODate("2015-01-16T03:33:15Z"),
"myState" : 1,
"members" : [
{
"_id" : 0,
"name" : "<span style="background-color: rgb(255, 0, 0);">localhost:28010</span>",
"health" : 0,
<span style="background-color: rgb(255, 0, 0);">"state" : 8,</span>
<span style="background-color: rgb(255, 0, 0);">"stateStr" : "(not reachable/healthy)",</span>
"uptime" : 0,
"optime" : Timestamp(1421378555, 1),
"optimeDate" : ISODate("2015-01-16T03:22:35Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:33:14Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:31:50Z"),
"pingMs" : 0
},
{
"_id" : 1,
"name" : <span style="color:#ff0000;">"localhost:28011</span>",
"health" : 1,
"state" : 1,
<span style="background-color: rgb(255, 0, 0);">"stateStr" : "PRIMARY"</span>,
"uptime" : 1608,
"optime" : Timestamp(1421378555, 1),
"optimeDate" : ISODate("2015-01-16T03:22:35Z"),
"electionTime" : Timestamp(1421379114, 1),
"electionDate" : ISODate("2015-01-16T03:31:54Z"),
"self" : true
},
{
"_id" : 2,
"name" : "localhost:28012",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 1358,
"optime" : Timestamp(1421378555, 1),
"optimeDate" : ISODate("2015-01-16T03:22:35Z"),
"lastHeartbeat" : ISODate("2015-01-16T03:33:15Z"),
"lastHeartbeatRecv" : ISODate("2015-01-16T03:33:13Z"),
"pingMs" : 0,
"lastHeartbeatMessage" : "syncing to: localhost:28011",
"syncingTo" : "localhost:28011"
}
],
"ok" : 1
}
rs1:PRIMARY> 此时28010的状态变为了8，描述为不可达。健康状态为0,28011的状态变为了1，描述为PRIMARY，此时的架构为如下所示：
rs1:PRIMARY> use test
switched to db test
rs1:PRIMARY> db.student.insert({name:"lisi",age:20});
WriteResult({ "nInserted" : 1 })
rs1:PRIMARY> db.student.find();
{ "_id" : ObjectId("54b883fb7bd891605d9c300f"), "name" : "zhangsan", "age" : 20 }
{ "_id" : ObjectId("54b8876aad5e04c1fe460154"), "name" : "lisi", "age" : 20 }
rs1:PRIMARY>
第五部分 架构篇 第十四章 MongoDB Replica Sets 架构（自动故障转移/读写分离实践）
原文地址：http://blog.csdn.net/xuzheng_java/article/details/42772973
