一角塑,概念
mongodb復(fù)制集是一主多從多節(jié)點(diǎn)實(shí)現(xiàn)數(shù)據(jù)庫(kù)集群的方式
1.1作用
首頁(yè)目標(biāo)是通過(guò)主節(jié)點(diǎn)快速的將oplog同步給從節(jié)點(diǎn)五慈,并在主節(jié)點(diǎn)發(fā)生故障的時(shí)候進(jìn)行選舉達(dá)到數(shù)據(jù)庫(kù)的高可用纳寂。
除此之外,還有:
- 數(shù)據(jù)分發(fā)—將數(shù)據(jù)從一個(gè)區(qū)域復(fù)制到另一個(gè)區(qū)域泻拦,減少另一個(gè)區(qū)域的讀延遲
- 讀寫(xiě)分離—不同類(lèi)型的壓力分別在不同的節(jié)點(diǎn)上執(zhí)行
- 異地容災(zāi)—在數(shù)據(jù)中心故障時(shí)候快速切換到異地
1.2數(shù)據(jù)分發(fā)過(guò)程
當(dāng)一個(gè)修改操作毙芜,無(wú)論是插入、更新或刪除争拐,到達(dá)主節(jié)點(diǎn)時(shí)腋粥,它對(duì)數(shù)據(jù)的操作將被
記錄下來(lái)(經(jīng)過(guò)一些必要的轉(zhuǎn)換),這些記錄稱(chēng)為 oplog。
從節(jié)點(diǎn)通過(guò)在主節(jié)點(diǎn)上打開(kāi)一個(gè) tailable 游標(biāo)不斷獲取新進(jìn)入主節(jié)點(diǎn)的 oplog隘冲,并
在自己的數(shù)據(jù)上回放闹瞧,以此保持跟主節(jié)點(diǎn)的數(shù)據(jù)一致。
1.3選舉過(guò)程
- 具有投票權(quán)的節(jié)點(diǎn)之間兩兩互相發(fā)送心跳展辞;
- 當(dāng)5次心跳未收到時(shí)判斷為節(jié)點(diǎn)失聯(lián)奥邮;
- 如果失聯(lián)的是主節(jié)點(diǎn),從節(jié)點(diǎn)會(huì)發(fā)起選舉纵竖,選出新的主節(jié)點(diǎn)漠烧;
- 如果失聯(lián)的是從節(jié)點(diǎn)則不會(huì)產(chǎn)生新的選舉杏愤;
- 選舉基于 RAFT一致性算法 實(shí)現(xiàn)靡砌,選舉成功的必要條件是大多數(shù)投票節(jié)點(diǎn)存活;
- 復(fù)制集中最多可以有50個(gè)節(jié)點(diǎn)珊楼,但具有投票權(quán)的節(jié)點(diǎn)最多7個(gè)通殃。
影響選舉的因素:
- 整個(gè)集群必須有大多數(shù)節(jié)點(diǎn)存活;
- 被選舉為主節(jié)點(diǎn)的節(jié)點(diǎn)必須:
1厕宗, 能夠與多數(shù)節(jié)點(diǎn)建立連接
2画舌,具有較新的 oplog
3,具有較高的優(yōu)先級(jí)(如果有配置)
二已慢,部署
準(zhǔn)備3份配置文件mongo1.conf曲聂,mongo2.conf,mongo3.conf
將端口號(hào)分別設(shè)置為28017/28018/28019
3個(gè)數(shù)據(jù)目錄:
/root/mongo/data/db1
/root/mongo/data/db2
/root/mongo/data/db3
3個(gè)日志文件路徑:
/root/mongo/data/db1/mongod.log
/root/mongo/data/db2/mongod.log
/root/mongo/data/db3/mongod.log
分別修改下面的配置
systemLog:
destination: file
path: /root/mongo/data/db1/mongod.log # log path
logAppend: true
storage:
dbPath: /root/mongo/data/db1 # data directory
net:
bindIp: 0.0.0.0
port: 28017 # port
replication:
replSetName: rs0
processManagement:
fork: true
啟動(dòng):
mongod -f mongo1.conf
mongod -f mongo2.conf
mongod -f mongo3.conf
//進(jìn)入第一個(gè)mongo
mongo --port 28017
//在mongo shell,初始化復(fù)制集并將節(jié)點(diǎn)加入復(fù)制集
rs.initiate({
_id: "rs0",
members: [{
_id: 0,
host: "localhost:28017"
},{
_id: 1,
host: "localhost:28018"
},{
_id: 2,
host: "localhost:28019"
}]
})
//mongo shell佑惠,查看整個(gè)復(fù)制集群狀態(tài)
rs.status()
//返回,具體含義:https://docs.mongodb.com/manual/reference/command/replSetGetStatus/#dbcmd.replSetGetStatus
{
"set" : "rs0",
"date" : ISODate("2021-01-19T17:57:06.050Z"),//復(fù)制集當(dāng)前時(shí)間朋腋,可以通過(guò)和members[n].lastHeartbeat比對(duì)來(lái)確定節(jié)點(diǎn)延遲
"myState" : 1,//0-10來(lái)代表節(jié)點(diǎn)不同狀態(tài),具體意思:https://docs.mongodb.com/manual/reference/replica-states/
"term" : NumberLong(1),//投票計(jì)數(shù)器
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"majorityVoteCount" : 2,
"writeMajorityCount" : 2,
"votingMembersCount" : 3,
"writableVotingMembersCount" : 3,
"optimes" : {
"lastCommittedOpTime" : {//當(dāng)前節(jié)點(diǎn)視角膜楷,最后已寫(xiě)入大多數(shù)副本集成員的最新操作的信息
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"lastCommittedWallTime" : ISODate("2021-01-19T17:56:56.332Z"),
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"readConcernMajorityWallTime" : ISODate("2021-01-19T17:56:56.332Z"),
"appliedOpTime" : {//最后應(yīng)用于當(dāng)前節(jié)點(diǎn)操作信息
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {//最后寫(xiě)入當(dāng)前節(jié)點(diǎn)日志操作信息
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"lastAppliedWallTime" : ISODate("2021-01-19T17:56:56.332Z"),
"lastDurableWallTime" : ISODate("2021-01-19T17:56:56.332Z")
},
"lastStableRecoveryTimestamp" : Timestamp(1611078996, 1),
"electionCandidateMetrics" : {
"lastElectionReason" : "electionTimeout",
"lastElectionDate" : ISODate("2021-01-19T17:51:36.306Z"),
"electionTerm" : NumberLong(1),
"lastCommittedOpTimeAtElection" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"lastSeenOpTimeAtElection" : {
"ts" : Timestamp(1611078684, 1),
"t" : NumberLong(-1)
},
"numVotesNeeded" : 2,
"priorityAtElection" : 1,
"electionTimeoutMillis" : NumberLong(10000),
"numCatchUpOps" : NumberLong(0),
"newTermStartDate" : ISODate("2021-01-19T17:51:36.319Z"),
"wMajorityWriteAvailabilityDate" : ISODate("2021-01-19T17:51:37.461Z")
},
"members" : [
{
"_id" : 0,
"name" : "localhost:28017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 783,
"optime" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-01-19T17:56:56Z"),
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1611078696, 1),
"electionDate" : ISODate("2021-01-19T17:51:36Z"),
"configVersion" : 1,
"configTerm" : 1,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "localhost:28018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 341,
"optime" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-01-19T17:56:56Z"),
"optimeDurableDate" : ISODate("2021-01-19T17:56:56Z"),
"lastHeartbeat" : ISODate("2021-01-19T17:57:04.311Z"),
"lastHeartbeatRecv" : ISODate("2021-01-19T17:57:05.814Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "localhost:28017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 1,
"configTerm" : 1
},
{
"_id" : 2,
"name" : "localhost:28019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 341,
"optime" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1611079016, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-01-19T17:56:56Z"),
"optimeDurableDate" : ISODate("2021-01-19T17:56:56Z"),
"lastHeartbeat" : ISODate("2021-01-19T17:57:04.312Z"),
"lastHeartbeatRecv" : ISODate("2021-01-19T17:57:05.815Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "localhost:28017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 1,
"configTerm" : 1
}
],
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1611079016, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1611079016, 1)
}
從節(jié)點(diǎn)默認(rèn)是備份節(jié)點(diǎn)旭咽,無(wú)法讀取數(shù)據(jù),將從節(jié)點(diǎn)設(shè)置成可讀從節(jié)點(diǎn)
rs.slaveOk()//舊版本
rs.secondaryOk()//新版本
嘗試主節(jié)點(diǎn)寫(xiě)入赌厅,從節(jié)點(diǎn)讀惹蠲唷:
//主
mongo localhost:28017
db.test.insert({ a:1 })
//從
mongo localhost:28018
db.test.find()