初識mongodb一二三(三)
三搭建mongodb副本集
MongoDB復制原理就是主節點記錄在其上的所有操作oplog,從節點定期輪詢主節點獲取這些操作,然後對自己的數據副本執行這些操作,從而保證從節點的數據與主節點一致。
那什麽是副本集呢?主從模式一主一從就是一個副本。MongoDB復制提供了數據的冗余備份,並在多個服務器上存儲數據副本,提高了數據的可用性, 並可以保證數據的安全性;復制還允許您從硬件故障和服務中斷中恢復數據。副本集具有多個副本保證了容錯性,就算一個副本掛掉了還有很多副本存在,並且解決了之前的問題“主節點掛掉了,整個集群內會自動切換”。
副本集特征:
· N 個節點的集群
· 任何節點可作為主節點
· 所有寫入操作都在主節點上
· 自動故障轉移
· 自動恢復
副本集還有以下幾個需要註意的地方:
1. 最小構成是:primary,secondary,arbiter,一般部署是:primary,2 secondary。
2. 成員數應該為奇數,如果為偶數的情況下添加arbiter,arbiter不保存數據,只投票。
3. 最大50 members,但是只能有 7 voting members,其他是non-voting members。
借用網上找的兩張架構圖說明一下:
由圖可以看到客戶端連接到整個副本集,不關心具體哪一臺機器是否掛掉。主服務器負責整個副本集的讀寫,副本集定期同步數據備份,一但主節點掛掉,副本節點就會選舉一個新的主服務器,這一切對於應用服務器不需要關心。我們看一下主服務器掛掉後的架構:
副本集中的副本節點在主節點掛掉後通過心跳機制檢測到後,就會在集群內發起主節點的選舉機制,自動選舉一位新的主服務器
官方推薦的副本集機器數量至少為3個,我這裏就以三個節點為例介紹。
1. 環境準備
192.168.221.161:27017作為主節點,192.168.221.161:27018,192.168.221.161:27019作為兩個副本節點
2. 分別創建三個節點所需要的文件夾
mkdir /data/db{1..3} #存放三個節點數據文件 touch /usr/local/mongodb/mongodb{1..3}.log #存放三個節點的日誌
3. 創建三個節點的配置文件
[root@MidApp mongodb]# cat mongodb1.conf dbpath=/data/db1 logpath=/usr/local/mongodb/logs/mongodb1.log logappend=true port=27017 fork=true auth=false nohttpinterface=false bind_ip=192.168.221.161 journal=true quiet=true replSet=repset
[root@MidApp mongodb]# cat mongodb2.conf dbpath=/data/db2 logpath=/usr/local/mongodb/logs/mongodb2.log logappend=true port=27018 fork=true auth=false nohttpinterface=false bind_ip=192.168.221.161 journal=true quiet=true replSet=repset
[root@MidApp mongodb]# cat mongodb3.conf dbpath=/data/db3 logpath=/usr/local/mongodb/logs/mongodb3.log logappend=true port=27019 fork=true auth=false nohttpinterface=false bind_ip=192.168.221.161 journal=true quiet=true replSet=repset
4. 分別啟動三個節點
mongod -f mongodb1.conf mongod -f mongodb2.conf mongod -f mongodb3.conf
查看日誌輸出,沒有找到replica的配置信息
2017-11-13T16:34:46.212-0800 I CONTROL [initandlisten] options: { config: "mongodb1.conf", net: { bindIp: "192.168.221.160", http: { enabled: true }, port: 27017 }, processManagement: { fork: true }, replication: { replSet: "repset" }, security: { authorization: "disabled" }, storage: { dbPath: "/data/db1", journal: { enabled: true } }, systemLog: { destination: "file", logAppend: true, path: "/usr/local/mongodb/logs/mongodb1.log", quiet: true } } 2017-11-13T16:34:46.214-0800 I INDEX [initandlisten] allocating new ns file /data/db1/local.ns, filling with zeroes... 2017-11-13T16:34:46.216-0800 I JOURNAL [journal writer] Journal writer thread started 2017-11-13T16:34:46.492-0800 I STORAGE [FileAllocator] allocating new datafile /data/db1/local.0, filling with zeroes... 2017-11-13T16:34:46.492-0800 I STORAGE [FileAllocator] creating directory /data/db1/_tmp 2017-11-13T16:34:46.501-0800 I STORAGE [FileAllocator] done allocating datafile /data/db1/local.0, size: 64MB, took 0.001 secs 2017-11-13T16:34:46.520-0800 I REPL [initandlisten] Did not find local replica set configuration document at startup; NoMatchingDocument Did not find replica set configuration document in local.system.replset
5. 初始化副本集
任選一個節點登錄進去,可以看到show dbs是不可用,因為還沒初始化副本集
[root@MidApp mongodb]# mongo 192.168.221.161 MongoDB shell version: 3.0.6 connecting to: 192.168.221.161/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 > show dbs 2017-11-13T16:39:33.235-0800 E QUERY Error: listDatabases failed:{ "note" : "from execCommand", "ok" : 0, "errmsg" : "not master" } at Error (<anonymous>) at Mongo.getDBs (src/mongo/shell/mongo.js:47:15) at shellHelper.show (src/mongo/shell/utils.js:630:33) at shellHelper (src/mongo/shell/utils.js:524:36) at (shellhelp2):1:1 at src/mongo/shell/mongo.js:47 > use admin switched to db admin
定義副本集配置變量,這裏的 _id:”repset” 和上面配置文件的參數“ –replSet repset” 要保持一樣
>config= {_id:"repset",members:[ {_id:0,host:"192.168.221.161:27017"}, {_id:1,host:"192.168.221.161:27018"}, {_id:2,host:"192.168.221.161:27019"}] }
查看輸出信息:
{ "_id" : "repset", "members" : [ { "_id" : 0, "host" : "192.168.221.161:27017" }, { "_id" : 1, "host" : "192.168.221.161:27018" }, { "_id" : 2, "host" : "192.168.221.161:27019" } ] }
初始化副本集配置
> rs.initiate(config); { "ok" : 1 }
查看集群節點狀態:
repset:OTHER> rs.status() { "set" : "repset", "date" : ISODate("2017-11-14T00:49:25.782Z"), "myState" : 1, "members" : [ { "_id" : 0, "name" : "192.168.221.161:27017", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 695, "optime" : Timestamp(1510620540, 1), "optimeDate" : ISODate("2017-11-14T00:49:00Z"), "electionTime" : Timestamp(1510620544, 1), "electionDate" : ISODate("2017-11-14T00:49:04Z"), "configVersion" : 1, "self" : true }, { "_id" : 1, "name" : "192.168.221.161:27018", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 25, "optime" : Timestamp(1510620540, 1), "optimeDate" : ISODate("2017-11-14T00:49:00Z"), "lastHeartbeat" : ISODate("2017-11-14T00:49:24.739Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T00:49:24.762Z"), "pingMs" : 0, "configVersion" : 1 }, { "_id" : 2, "name" : "192.168.221.161:27019", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 25, "optime" : Timestamp(1510620540, 1), "optimeDate" : ISODate("2017-11-14T00:49:00Z"), "lastHeartbeat" : ISODate("2017-11-14T00:49:24.739Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T00:49:24.762Z"), "pingMs" : 0, "configVersion" : 1 } ], "ok" : 1 }
整個副本及已經搭建成功了!
6. 測試副本集數據復制功能
在主節點登錄mongodb
[root@MidApp mongodb]# mongo 192.168.221.161:27017 MongoDB shell version: 3.0.6 connecting to: 192.168.221.161:27017/test repset:PRIMARY> use test; switched to db test repset:PRIMARY> db.testdb.insert({"test1":"item1"}) WriteResult({ "nInserted" : 1 }) repset:PRIMARY> exit bye
在副本節點登錄查看數據:
[root@MidApp logs]# mongo 192.168.221.161:27018 MongoDB shell version: 3.0.6 connecting to: 192.168.221.161:27018/test repset:SECONDARY> use test switched to db test repset:SECONDARY> db.getMongo().setSlaveOk();#mongodb默認是從主節點讀寫數據的,副本節點上不允許讀,需要設置副本節點可以讀 repset:SECONDARY> db.testdb.find() { "_id" : ObjectId("5a0a3e8d40637405ab003b39"), "test1" : "item1" }
7. 測試副本集failover功能
手動把現在的主節點停掉,查看集群狀態:
repset:SECONDARY> rs.status() { "set" : "repset", "date" : ISODate("2017-11-14T00:57:14.753Z"), "myState" : 2, "members" : [ { "_id" : 0, "name" : "192.168.221.161:27017", "health" : 0, "state" : 8, "stateStr" : "(not reachable/healthy)", "uptime" : 0, "optime" : Timestamp(0, 0), "optimeDate" : ISODate("1970-01-01T00:00:00Z"), "lastHeartbeat" : ISODate("2017-11-14T00:57:13.304Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T00:57:09.285Z"), "pingMs" : 0, "lastHeartbeatMessage" : "Failed attempt to connect to 192.168.221.161:27017; couldn‘t connect to server 192.168.221.161:27017 (192.168.221.161), connection attempt failed", "configVersion" : -1 }, { "_id" : 1, "name" : "192.168.221.161:27018", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 1167, "optime" : Timestamp(1510620813, 2), "optimeDate" : ISODate("2017-11-14T00:53:33Z"), "infoMessage" : "could not find member to sync from", "configVersion" : 1, "self" : true }, { "_id" : 2, "name" : "192.168.221.161:27019", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 17, "optime" : Timestamp(1510620813, 2), "optimeDate" : ISODate("2017-11-14T00:53:33Z"), "lastHeartbeat" : ISODate("2017-11-14T00:57:13.317Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T00:57:13.330Z"), "pingMs" : 0, "electionTime" : Timestamp(1510621032, 1), "electionDate" : ISODate("2017-11-14T00:57:12Z"), "configVersion" : 1 } ], "ok" : 1 }
可以看到原來的主節點狀態現在已經變成了不可達,192.168.221.161:27019已經變成新的主節點
8. 再次啟動原來的主節點,發現192.168.221.161:27017還是SECONDARY
repset:SECONDARY> rs.status() { "set" : "repset", "date" : ISODate("2017-11-14T17:02:13.837Z"), "myState" : 2, "members" : [ { "_id" : 0, "name" : "192.168.221.161:27017", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 5, "optime" : Timestamp(1510620813, 2), "optimeDate" : ISODate("2017-11-14T00:53:33Z"), "lastHeartbeat" : ISODate("2017-11-14T17:02:12.642Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T17:02:11.902Z"), "pingMs" : 0, "configVersion" : 1 }, { "_id" : 1, "name" : "192.168.221.161:27018", "health" : 1, "state" : 2, "stateStr" : "SECONDARY", "uptime" : 59066, "optime" : Timestamp(1510620813, 2), "optimeDate" : ISODate("2017-11-14T00:53:33Z"), "configVersion" : 1, "self" : true }, { "_id" : 2, "name" : "192.168.221.161:27019", "health" : 1, "state" : 1, "stateStr" : "PRIMARY", "uptime" : 57916, "optime" : Timestamp(1510620813, 2), "optimeDate" : ISODate("2017-11-14T00:53:33Z"), "lastHeartbeat" : ISODate("2017-11-14T17:02:12.308Z"), "lastHeartbeatRecv" : ISODate("2017-11-14T17:02:12.080Z"), "pingMs" : 0, "electionTime" : Timestamp(1510621032, 1), "electionDate" : ISODate("2017-11-14T00:57:12Z"), "configVersion" : 1 } ], "ok" : 1 }
現在,mongodb的副本集群已經完成了。
關於mongodb的讀寫分離和分片的內容以後有時間繼續學習···
本文出自 “清渺淡寫” 博客,請務必保留此出處http://qingmiao.blog.51cto.com/7286083/1981700
初識mongodb一二三(三)