MongoDB復制集（即主從復制）

發布時間：2020-02-29 02:53:53 來源：網絡閱讀：5020 作者：MaAiQiang 欄目：MongoDB數據庫

MongoDB 復制集

MongoDB復制是將數據同步到多個服務器的過程；
復制集提供了數據的冗余備份并提高了數據的可用性，通常可以保證數據的安全性；
復制集還允許您從硬件故障和服務中斷中恢復數據。

什么是復制集?

保障數據的安全性
數據高可用性 (24*7)
災難恢復
無需停機維護（如備份，重建索引，壓縮）
分布式讀取數據
副本集對應用層是透明的

MongoDB復制集的工作原理

mongodb的復制集至少需要兩個節點。其中一個是主節點，負責處理客戶端請求，其余的都是從節點，負責復制主節點上的數據。

mongodb各個節點常見的搭配方式為：一主一從、一主多從。

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，然后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。

MongoDB復制結構圖如下所示：

MongoDB復制集（即主從復制）

（以上圖片引用網址：http://www.runoob.com/mongodb/mongodb-replication.html ）

以上結構圖中，客戶端從主節點讀取數據，在客戶端寫入數據到主節點時，主節點與從節點進行數據交互保障數據的一致性。

復制集的特點：

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

如何部署MongoDB復制集？

在同一臺服務器上創建MongoDB的多實例（4個實例）來做MongoDB主從的實驗。

至于如何安裝MongoDB？請參考之前博文 Linux 平臺安裝MongoDB 4.0（最新版）

開始部署

1.創建4個MongoDB的實例

#創建各實例的數據目錄
mkdir -p /data/mongodb/mongodb{1,2,3,4}

#創建實例配置目錄
mkdir -p /data/conf/

#創建實例的日志目錄
mkdir -p /data/logs/

#創建各實例的日志文件
touch  /data/logs/mongodb{1,2,3,4}.log

#賦予日志文件權限777
chmod 777 /data/logs/*.log

2.編輯mongodb1.conf配置文件，開啟復制集功能并配置replSetName參數

vim /data/mongodb/mongodb1.conf

#mongod.conf
#for documentation of all options, see:
#http://docs.mongodb.org/manual/reference/configuration-options/
#where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /data/logs/mongodb1.log         //mongodb1的日志文件路徑
#Where and how to store data.
storage:
  dbPath: /data/mongodb/mongodb1/          //mongodb1的數據文件路徑
  journal:
    enabled: true
#engine:
#mmapv1:
#wiredTiger:
#how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /data/mongodb/mongodb1/mongod.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo
#network interfaces
net:
  port: 27017                   //mongodb1的進程號
  bindIp: 0.0.0.0  # Listen to local interface only, comment to listen on all interfaces.
#security:
#operationProfiling:
replication:                   //刪除“#”，開啟復制集功能
    replSetName: test-rc       //名稱為test-rc
#sharding:
##Enterprise-Only Options
#auditLog:
#snmp:

3.復制默認mongodb1.conf配置文件，生成另外三份實例的配置文件

#復制默認實例的配置文件

cp -p /data/mongodb/mongodb1.conf /data/conf/mongodb2.conf
cp -p /data/mongodb/mongodb1.conf /data/conf/mongodb3.conf
cp -p /data/mongodb/mongodb1.conf /data/conf/mongodb4.conf

4.分別修改mongodb2.conf、mongodb3.conf、mongodb4.conf配置文件，如下

MongoDB2配置文件

cat /data/conf/mongodb2.conf

#mongod.conf
#for documentation of all options, see:
#http://docs.mongodb.org/manual/reference/configuration-options/
#where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /data/logs/mongodb2.log         //mongodb2的日志文件路徑
#Where and how to store data.
storage:
  dbPath: /data/mongodb/mongodb2/          //mongodb2的數據文件路徑
  journal:
    enabled: true
#engine:
#mmapv1:
#wiredTiger:
#how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /data/mongodb/mongodb1/mongod.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo
#network interfaces
net:
  port: 27018                   //mongodb2的進程號
  bindIp: 0.0.0.0  # Listen to local interface only, comment to listen on all interfaces.
#security:
#operationProfiling:
replication:                    //刪除“#”，開啟復制集功能
    replSetName: test-rc        #名稱為test-rc
#sharding:
##Enterprise-Only Options
#auditLog:
#snmp:

MongoDB3配置文件

cat /data/conf/mongodb3.conf

#mongod.conf
#for documentation of all options, see:
#http://docs.mongodb.org/manual/reference/configuration-options/
#where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /data/logs/mongodb3.log         //mongodb3的日志文件路徑
#Where and how to store data.
storage:
  dbPath: /data/mongodb/mongodb3/          //mongodb3的數據文件路徑
  journal:
    enabled: true
#engine:
#mmapv1:
#wiredTiger:
#how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /data/mongodb/mongodb1/mongod.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo
#network interfaces
net:
  port: 27019                   //mongodb3的進程號
  bindIp: 0.0.0.0  # Listen to local interface only, comment to listen on all interfaces.
#security:
#operationProfiling:
replication:                    //刪除“#”，開啟復制集功能
    replSetName: test-rc        #名稱為test-rc
#sharding:
##Enterprise-Only Options
#auditLog:
#snmp:

MongoDB4配置文件

cat /data/conf/mongodb4.conf

#mongod.conf
#for documentation of all options, see:
#http://docs.mongodb.org/manual/reference/configuration-options/
#where to write logging data.
systemLog:
  destination: file
  logAppend: true
  path: /data/logs/mongodb4.log        //mongodb4的日志文件路徑
#Where and how to store data.
storage:
  dbPath: /data/mongodb/mongodb4/          //mongodb4的數據文件路徑
  journal:
    enabled: true
#engine:
#mmapv1:
#wiredTiger:
#how the process runs
processManagement:
  fork: true  # fork and run in background
  pidFilePath: /data/mongodb/mongodb1/mongod.pid  # location of pidfile
  timeZoneInfo: /usr/share/zoneinfo
#network interfaces
net:
  port: 27020                   //mongodb4的進程號
  bindIp: 0.0.0.0  # Listen to local interface only, comment to listen on all interfaces.
#security:
#operationProfiling:
replication:                    //刪除“#”，開啟復制集功能
    replSetName: test-rc        //名稱為test-rc
#sharding:
##Enterprise-Only Options
#auditLog:
#snmp:

5. 啟動mongodb多實例

for i in 1 2 3 4
do
        mongod -f /data/conf/mongodb$i.conf
done

檢查mongod的進程信息

[root@localhost conf]# netstat -tunlp | grep mongod

MongoDB復制集（即主從復制）

6.開始配置三個節點的復制集

6.1 登錄默認MongoDB（默認端口號為：27017）

mongo

6.2 查看復制集的狀態信息

> rs.status()

MongoDB復制集（即主從復制）

6.3 定義cfg初始化參數(這里先加入三臺，另一臺后面實現添加節點功能)

> cfg={"_id":"test-rc","members":[{"_id":0,"host":"192.168.100.100:27017"},{"_id":1,"host":"192.168.100.100:27018"},{"_id":2,"host":"192.168.100.100:27019"}]}

MongoDB復制集（即主從復制）

6.4 啟動復制集功能（初始化配置時保證從節點沒有數據）

> rs.initiate(cfg)

MongoDB復制集（即主從復制）

6.5 查看復制集的狀態信息

test-rc:PRIMARY> rs.status()

{
    "set" : "test-rc",
    "date" : ISODate("2018-07-14T04:46:58.710Z"),
    "myState" : 1,
    "term" : NumberLong(1),
    "syncingTo" : "",
    "syncSourceHost" : "",
    "syncSourceId" : -1,
    "heartbeatIntervalMillis" : NumberLong(2000),
    "optimes" : {
        "lastCommittedOpTime" : {
            "ts" : Timestamp(1531543618, 1),
            "t" : NumberLong(1)
        },
        "readConcernMajorityOpTime" : {
            "ts" : Timestamp(1531543618, 1),
            "t" : NumberLong(1)
        },
        "appliedOpTime" : {
            "ts" : Timestamp(1531543618, 1),
            "t" : NumberLong(1)
        },
        "durableOpTime" : {
            "ts" : Timestamp(1531543618, 1),
            "t" : NumberLong(1)
        }
    },
    "lastStableCheckpointTimestamp" : Timestamp(1531543608, 1),
    "members" : [
        {
            "_id" : 0,
            "name" : "192.168.100.100:27017",
            "health" : 1,               //健康狀態
            "state" : 1,                //1：為主節點   ；  2：為從節點
            "stateStr" : "PRIMARY",         //主節點
            "uptime" : 2886,
            "optime" : {
                "ts" : Timestamp(1531543618, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-14T04:46:58Z"),
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "",
            "electionTime" : Timestamp(1531543426, 1),
            "electionDate" : ISODate("2018-07-14T04:43:46Z"),
            "configVersion" : 1,
            "self" : true,
            "lastHeartbeatMessage" : ""
        },
        {
            "_id" : 1,
            "name" : "192.168.100.100:27018",
            "health" : 1,               //健康狀態
            "state" : 2,                //1：為主節點   ；  2：為從節點
            "stateStr" : "SECONDARY",         //從節點
            "uptime" : 202,
            "optime" : {
                "ts" : Timestamp(1531543608, 1),
                "t" : NumberLong(1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531543608, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-14T04:46:48Z"),
            "optimeDurableDate" : ISODate("2018-07-14T04:46:48Z"),
            "lastHeartbeat" : ISODate("2018-07-14T04:46:56.765Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-14T04:46:57.395Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.100.100:27017",
            "syncSourceHost" : "192.168.100.100:27017",
            "syncSourceId" : 0,
            "infoMessage" : "",
            "configVersion" : 1
        },
        {
            "_id" : 2,
            "name" : "192.168.100.100:27019",
            "health" : 1,               //健康狀態
            "state" : 2,                //1：為主節點   ；  2：為從節點
            "stateStr" : "SECONDARY",         //從節點
            "uptime" : 202,
            "optime" : {
                "ts" : Timestamp(1531543608, 1),
                "t" : NumberLong(1)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531543608, 1),
                "t" : NumberLong(1)
            },
            "optimeDate" : ISODate("2018-07-14T04:46:48Z"),
            "optimeDurableDate" : ISODate("2018-07-14T04:46:48Z"),
            "lastHeartbeat" : ISODate("2018-07-14T04:46:56.769Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-14T04:46:57.441Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.100.100:27017",
            "syncSourceHost" : "192.168.100.100:27017",
            "syncSourceId" : 0,
            "infoMessage" : "",
            "configVersion" : 1
        }
    ],
    "ok" : 1,
    "operationTime" : Timestamp(1531543618, 1),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1531543618, 1),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}

特別提醒：如以上可知道主節點在192.168.100.100:27017節點上

注意：嚴禁在從庫做任何修改操作

7. 添加節點

test-rc:PRIMARY>  rs.add("192.168.100.100:27020")

MongoDB復制集（即主從復制）

查看復制集的狀態信息

test-rc:PRIMARY>  rs.status()

MongoDB復制集（即主從復制）

8. 刪除節點

test-rc:PRIMARY>  rs.remove("192.168.100.100:27018")

MongoDB復制集（即主從復制）

查看復制集的狀態信息

test-rc:PRIMARY>  rs.status()

發現192.168.100.100:27018節點已經沒有相關信息了

9. 故障轉移切換

9.1 退出MongoDB

test-rc:PRIMARY> exit

9.2 查看mongod進程信息

netstat -tunlp | grep mongod

MongoDB復制集（即主從復制）

可以查看到共有4個實例的進程信息

9.3 結束主節點：端口號為27017的進程，檢查是否能夠自動切換

kill -9 48211

MongoDB復制集（即主從復制）

9.4 登錄MongoDB端口號為27019的實例

mongo --port 27019

9.5 查看各節點狀態信息

test-rc:PRIMARY>  rs.status()

{
            "_id" : 2,
            "name" : "192.168.100.100:27019",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 1547,
            "optime" : {
                "ts" : Timestamp(1531544567, 1),
                "t" : NumberLong(2)
            },
            "optimeDate" : ISODate("2018-07-14T05:02:47Z"),
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "",
            "electionTime" : Timestamp(1531544345, 1),
            "electionDate" : ISODate("2018-07-14T04:59:05Z"),
            "configVersion" : 3,
            "self" : true,
            "lastHeartbeatMessage" : ""
        },
        {
            "_id" : 3,
            "name" : "192.168.100.100:27020",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 700,
            "optime" : {
                "ts" : Timestamp(1531544567, 1),
                "t" : NumberLong(2)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531544567, 1),
                "t" : NumberLong(2)
            },
            "optimeDate" : ISODate("2018-07-14T05:02:47Z"),
            "optimeDurableDate" : ISODate("2018-07-14T05:02:47Z"),
            "lastHeartbeat" : ISODate("2018-07-14T05:02:56.150Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-14T05:02:56.289Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.100.100:27019",
            "syncSourceHost" : "192.168.100.100:27019",
            "syncSourceId" : 2,
            "infoMessage" : "",
            "configVersion" : 3
        }

特別提醒：主節點已經到192.168.100.100:27019節點上，說明主節點已經自動切換了

10. 手動切換主節點

10.1 暫停30s不參與選舉

test-rc:PRIMARY> rs.freeze(30)

{
    "operationTime" : Timestamp(1531544867, 1),
    "ok" : 0,
    "errmsg" : "cannot freeze node when primary or running for election. state: Primary",
    "code" : 95,
    "codeName" : "NotSecondary",
    "$clusterTime" : {
        "clusterTime" : Timestamp(1531544867, 1),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}

10.2 交出主節點位置，維持從節點狀態不少于60秒，等待30秒使主節點和從節點日志同步

test-rc:PRIMARY> rs.stepDown(60,30)

> test-rc:PRIMARY> rs.stepDown(60,30)

2018-07-14T01:08:07.326-0400 E QUERY    [js] Error: error doing query: failed: network error while attempting to run command 'replSetStepDown' on host '127.0.0.1:27019'  :
DB.prototype.runCommand@src/mongo/shell/db.js:168:1
DB.prototype.adminCommand@src/mongo/shell/db.js:186:16
rs.stepDown@src/mongo/shell/utils.js:1398:12
@(shell):1:1
2018-07-14T01:08:07.328-0400 I NETWORK  [js] trying reconnect to 127.0.0.1:27019 failed
2018-07-14T01:08:07.329-0400 I NETWORK  [js] reconnect 127.0.0.1:27019 ok

10.3 查看復制集的狀態信息

> test-rc:PRIMARY> rs.status()

{
    "set" : "test-rc",
    "date" : ISODate("2018-07-14T05:10:31.161Z"),
    "myState" : 2,
    "term" : NumberLong(3),
    "syncingTo" : "192.168.100.100:27020",
    "syncSourceHost" : "192.168.100.100:27020",
    "syncSourceId" : 3,
    "heartbeatIntervalMillis" : NumberLong(2000),
    "optimes" : {
        "lastCommittedOpTime" : {
            "ts" : Timestamp(1531545028, 1),
            "t" : NumberLong(3)
        },
        "readConcernMajorityOpTime" : {
            "ts" : Timestamp(1531545028, 1),
            "t" : NumberLong(3)
        },
        "appliedOpTime" : {
            "ts" : Timestamp(1531545028, 1),
            "t" : NumberLong(3)
        },
        "durableOpTime" : {
            "ts" : Timestamp(1531545028, 1),
            "t" : NumberLong(3)
        }
    },
    "lastStableCheckpointTimestamp" : Timestamp(1531545018, 1),
    "members" : [
        {
            "_id" : 0,
            "name" : "192.168.100.100:27017",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 70,
            "optime" : {
                "ts" : Timestamp(1531545028, 1),
                "t" : NumberLong(3)
            },
            "optimeDate" : ISODate("2018-07-14T05:10:28Z"),
            "syncingTo" : "192.168.100.100:27020",
            "syncSourceHost" : "192.168.100.100:27020",
            "syncSourceId" : 3,
            "infoMessage" : "",
            "configVersion" : 3,
            "self" : true,
            "lastHeartbeatMessage" : ""
        },
        {
            "_id" : 2,
            "name" : "192.168.100.100:27019",
            "health" : 1,
            "state" : 2,
            "stateStr" : "SECONDARY",
            "uptime" : 68,
            "optime" : {
                "ts" : Timestamp(1531545028, 1),
                "t" : NumberLong(3)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531545028, 1),
                "t" : NumberLong(3)
            },
            "optimeDate" : ISODate("2018-07-14T05:10:28Z"),
            "optimeDurableDate" : ISODate("2018-07-14T05:10:28Z"),
            "lastHeartbeat" : ISODate("2018-07-14T05:10:30.079Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-14T05:10:31.094Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "192.168.100.100:27020",
            "syncSourceHost" : "192.168.100.100:27020",
            "syncSourceId" : 3,
            "infoMessage" : "",
            "configVersion" : 3
        },
        {
            "_id" : 3,
            "name" : "192.168.100.100:27020",
            "health" : 1,
            "state" : 1,
            "stateStr" : "PRIMARY",
            "uptime" : 68,
            "optime" : {
                "ts" : Timestamp(1531545028, 1),
                "t" : NumberLong(3)
            },
            "optimeDurable" : {
                "ts" : Timestamp(1531545028, 1),
                "t" : NumberLong(3)
            },
            "optimeDate" : ISODate("2018-07-14T05:10:28Z"),
            "optimeDurableDate" : ISODate("2018-07-14T05:10:28Z"),
            "lastHeartbeat" : ISODate("2018-07-14T05:10:30.079Z"),
            "lastHeartbeatRecv" : ISODate("2018-07-14T05:10:29.561Z"),
            "pingMs" : NumberLong(0),
            "lastHeartbeatMessage" : "",
            "syncingTo" : "",
            "syncSourceHost" : "",
            "syncSourceId" : -1,
            "infoMessage" : "",
            "electionTime" : Timestamp(1531544897, 1),
            "electionDate" : ISODate("2018-07-14T05:08:17Z"),
            "configVersion" : 3
        }
    ],
    "ok" : 1,
    "operationTime" : Timestamp(1531545028, 1),
    "$clusterTime" : {
        "clusterTime" : Timestamp(1531545028, 1),
        "signature" : {
            "hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
            "keyId" : NumberLong(0)
        }
    }
}

特別提醒：此刻主節點已經在192.168.100.100:27020節點上

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