mongodb中的副本集搭建实践

准备运行1个主节点,2个从节点,从节点中其中是一个是仲裁节点(Arb)。

sudo mongod --replSet application --dbpath /data/node1/ --port 9927 --oplogSize 1024
sudo mongod --replSet application --dbpath /data/node2/ --port 9928 --oplogSize 1024
sudo mongod --replSet application --dbpath /data/arbiter/ --port 9929 --oplogSize 1024

其中application是副本集的名称,节点必须相同,–dbpath指定数据库储存路径,–port指定侦听端口,–oplogSize指定数据同步之前的缓存的空间大小,暂时指定1G。选择9927端口的实例为主节点,进入9927的shell:

mongo localhost:9927

初始化副本集需要配置表,申明配置表如下:

config = {_id: "application", members: []}

注意_id和副本集启动的共享名称一致。下面来逐步添加节点的数据信息:

config.members.push({_id: 0, host: "localhost:9927"})
config.members.push({_id: 1, host: "localhost:9928"})
config.members.push({_id: 2, host: "localhost:9929", arbiterOnly: true})

也可以使用rs.add和rs.addArb函数来实现同样的操作。然后需要用这个表作为参数初始化副本集,在9927端口的shell执行:

> rs.initiate(config)
{
  "info" : "Config now saved locally.  Should come online in about a minute.",
  "ok" : 1
}

返回ok为1表示初始化成功,三个节点互相检测通信,需要1分钟左右(反应够慢的 ^-),可以查看三个终端窗口的信息确认,完成通信后,在9927端口的shell回车执行命令确认配置:

> rs.isMaster()
{
  "setName" : "application",
  "ismaster" : true,
  "secondary" : false,
  "hosts" : [
      "localhost:9927",
      "localhost:9928"
  ],
  "arbiters" : [
      "localhost:9929"
  ],
  "primary" : "localhost:9927",
  "me" : "localhost:9927",
  "maxBsonObjectSize" : 16777216,
  "localTime" : ISODate("2013-01-26T13:34:03.378Z"),
  "ok" : 1
}

注意到9927端口的实例ismaster是true,secondary为false,hosts有2个实例,arbiter有1个元素,primary关键key表示了主节点,通信完成几次回车后可以看到9927的端口的实例shell的提示符已经改变,更改为application:PRIMARY,查看更详细的信息:

application:PRIMARY> rs.status()
{
  "set" : "application",
  "date" : ISODate("2013-01-26T13:34:35Z"),
  "myState" : 1,
  "members" : [
      {
          "_id" : 0,
          "name" : "localhost:9927",
          "health" : 1,
          "state" : 1,
          "stateStr" : "PRIMARY",
          "uptime" : 140,
          "optime" : Timestamp(1359207200000, 1),
          "optimeDate" : ISODate("2013-01-26T13:33:20Z"),
          "self" : true
      },
      {
          "_id" : 1,
          "name" : "localhost:9928",
          "health" : 1,
          "state" : 2,
          "stateStr" : "SECONDARY",
          "uptime" : 63,
          "optime" : Timestamp(1359207200000, 1),
          "optimeDate" : ISODate("2013-01-26T13:33:20Z"),
          "lastHeartbeat" : ISODate("2013-01-26T13:34:34Z"),
          "pingMs" : 0
      },
      {
          "_id" : 2,
          "name" : "localhost:9929",
          "health" : 1,
          "state" : 7,
          "stateStr" : "ARBITER",
          "uptime" : 63,
          "lastHeartbeat" : ISODate("2013-01-26T13:34:34Z"),
          "pingMs" : 0
      }
  ],
  "ok" : 1
}

显示了每个节点的健康状况,名称,启动的时间,节点的类型等。查看当前副本集的配置表:

application:PRIMARY> rs.conf()
{
  "_id" : "application",
  "version" : 1,
  "members" : [
      {
          "_id" : 0,
          "host" : "localhost:9927"
      },
      {
          "_id" : 1,
          "host" : "localhost:9928"
      },
      {
          "_id" : 2,
          "host" : "localhost:9929",
          "arbiterOnly" : true
      }
  ]
}

插入测试数据:

application:PRIMARY> db.users.insert({username: "visionwang", age: 26})

进入9928从节点,执行查看集合:

application:SECONDARY> show collections
application:SECONDARY> show collections
Sat Jan 26 21:39:40 uncaught exception: error: { "$err" : "not master and slaveOk=false", "code" : 13435 }

发现shell抛出了异常,显示slaveOK为false,当前副本集需要明确从节点参数,执行函数:

application:SECONDARY> rs.slaveOk()
application:SECONDARY> show collections
system.indexes
users

查询测试数据:

application:SECONDARY> db.users.find()
{ "_id" : ObjectId("5103dbc8f556a05a96a28e69"), "username" : "visionwang", "age" : 26 }

插入数据没有抛出异常,但是显示not master,表示当前从节点是只读的:

application:SECONDARY> db.users.insert({username: "nl", age: 25})
not master

切换到9927主节点,使用系统空间库查询副本集信息:

application:PRIMARY> db.system.replset.findOne()
{
  "_id" : "application",
  "version" : 1,
  "members" : [
      {
          "_id" : 0,
          "host" : "localhost:9927"
      },
      {
          "_id" : 1,
          "host" : "localhost:9928"
      },
      {
          "_id" : 2,
          "host" : "localhost:9929",
          "arbiterOnly" : true
      }
  ]
}
application:PRIMARY> db.getReplicationInfo()
{
  "logSizeMB" : 1024,
  "usedMB" : 0.01,
  "timeDiff" : 169,
  "timeDiffHours" : 0.05,
  "tFirst" : "Sat Jan 26 2013 21:33:20 GMT+0800 (CDT)",
  "tLast" : "Sat Jan 26 2013 21:36:09 GMT+0800 (CDT)",
  "now" : "Sat Jan 26 2013 21:48:07 GMT+0800 (CDT)"
}

进入9929端口,可以看到仲裁节点的提示符号:

mongo localhost:9929
application:ARBITER> 

执行故障转移测试,可以ctrl+c掉9927的主节点,观察终端信息提示,9927处于down状态,9928从节点自举为主节点,回车后发现shell提示符号已经更改为application:PRIMARY,再将9927上线,添加为从节点,再ctrl+c掉9928节点,经过少许时间,9927端口又恢复成主节点,再将9928上线,系统恢复到初始的副本集,仲裁节点的作用是协调leader选举,监测系统运行状态,提供节点互相通讯的数据信息。

mongodb也支持简单的主从复制,但是有了强大的副本集,几乎找不到什么理由使用简单的主从复制策略,甚至mongodb的分片(auto-sharding)也是使用副本集实现。

51CTO也有一个windows上面的版本http://database.51cto.com/art/201301/379033.htm。

posted @ 2013-08-29 22:09 visionwang 阅读(...) 评论(...) 编辑 收藏