MongoDB学习之复制集
小勇勇 -
主要为了实现mongodb服务的高可用，复制集之间是一种主从关系
由上面的特点，我们对redis了解的话，可以很快联想到哨兵模式
在除了以上的数据同步和故障节点替换两大特性以外，复制集还存在以下作用
数据分发：将数据分发到不同的区域，减少读的延迟
例如公司在北京、上海、广州都有数据中心，但只有北京的是可以写入的中心，可将数据异地分发，提高上海和广州大区用户的读取效率。
读写分离异地容灾：数据中心故障时快速切换到异地。复制集的结构复制集的结构与其它中间件的主从模式基本类似。
一个典型的复制集由3个及以上具有投票的节点组成：
主节点：只有一个，负责数据的写入和读取，以及选举时投票。从节点：至少有两个，负责数据读取和选举投票。数据的复制原理
当数据(主节点)发生修改(增删改)时，它对数据的操作将被记录在一个oplog文件当中。从节点通过在主节点上代开一个tailable游标不断获取主节点中新增的oplog并且不断在自己的节点上重现这些操作，以此来实现和主节点上的数据一致。主节点选举原理
具有投票权的节点之间两两互相发送心跳。当5次心跳未收到时判断为节点失联。如果主节点失联，从节点会选出新的主节点，但失联的从节点不会参与选举。选举基于RAFT一致性算法实现，选举成功的必要条件是大多数投票节点存活。复制集中最多可有50个节点，但有投票权的最多有7个。被选举为主节点的的节点 必须能与多数节点建立连接、有比较新的oplog、比较高的优先级(如果配置中有)搭建一个复制集下面是在linux下创建一个mongodb复制集
mkdir -p /data/mongodb/db{1,2,3}#节点1
systemLog:
destination: file
path: /data/mongodb/db1/mongod.log #日志路径
logAppend: true
storage:
dbPath: /data/mongodb/db1 #数据文件
net:
bindIp: 0.0.0.0 #在所有网卡监听，为了外网访问
port: 28017
replication: #复制集，没有的话就是一个单节点
replSetName: rs0 #复制集名字
processManagement:
fork: true #把进程作为独立的后台进程进程
#节点2
systemLog:
destination: file
path: /data/mongodb/db2/mongod.log #日志路径
logAppend: true
storage:
dbPath: /data/mongodb/db2 #数据文件
net:
bindIp: 0.0.0.0 #在所有网卡监听，为了外网访问
port: 28018
replication: #复制集，没有的话就是一个单节点
replSetName: rs0 #复制集名字
processManagement:
fork: true #把进程作为独立的后台进程进程
#节点3
systemLog:
destination: file
path: /data/mongodb/db3/mongod.log #日志路径
logAppend: true
storage:
dbPath: /data/mongodb/db3 #数据文件
net:
bindIp: 0.0.0.0 #在所有网卡监听，为了外网访问
port: 28019
replication: #复制集，没有的话就是一个单节点
replSetName: rs0 #复制集名字
processManagement:
fork: true #把进程作为独立的后台进程进程mongod -f db1/mongod.conf
mongod -f db2/mongod.conf
mongod -f db3/mongod.conf进入主节点
mongo --port 28017
设置主节点
rs.initiate()
{
"info2" : "no configuration specified. Using a default configuration for the set",
"me" : "supman:28017",
"ok" : 1
}查看节点状态
rs.status()
{
"set" : "rs0",
"date" : ISODate("2021-11-30T15:33:30.616Z"),
"myState" : 1,
"term" : NumberLong(1),
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"majorityVoteCount" : 1,
"writeMajorityCount" : 1,
"votingMembersCount" : 1,
"writableVotingMembersCount" : 1,
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1638286404, 1),
"t" : NumberLong(1)
},
"lastCommittedWallTime" : ISODate("2021-11-30T15:33:24.656Z"),
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1638286404, 1),
"t" : NumberLong(1)
},
"readConcernMajorityWallTime" : ISODate("2021-11-30T15:33:24.656Z"),
"appliedOpTime" : {
"ts" : Timestamp(1638286404, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1638286404, 1),
"t" : NumberLong(1)
},
"lastAppliedWallTime" : ISODate("2021-11-30T15:33:24.656Z"),
"lastDurableWallTime" : ISODate("2021-11-30T15:33:24.656Z")
},
"lastStableRecoveryTimestamp" : Timestamp(1638286364, 1),
"electionCandidateMetrics" : {
"lastElectionReason" : "electionTimeout",
"lastElectionDate" : ISODate("2021-11-30T15:27:54.614Z"),
"electionTerm" : NumberLong(1),
"lastCommittedOpTimeAtElection" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"lastSeenOpTimeAtElection" : {
"ts" : Timestamp(1638286074, 1),
"t" : NumberLong(-1)
},
"numVotesNeeded" : 1,
"priorityAtElection" : 1,
"electionTimeoutMillis" : NumberLong(10000),
"newTermStartDate" : ISODate("2021-11-30T15:27:54.637Z"),
"wMajorityWriteAvailabilityDate" : ISODate("2021-11-30T15:27:54.660Z")
},
"members" : [
{
"_id" : 0,
"name" : "supman:28017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1227,
"optime" : {
"ts" : Timestamp(1638286404, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-11-30T15:33:24Z"),
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1638286074, 2),
"electionDate" : ISODate("2021-11-30T15:27:54Z"),
"configVersion" : 1,
"configTerm" : 1,
"self" : true,
"lastHeartbeatMessage" : ""
}
],
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1638286404, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1638286404, 1)
}找到status信息里面的 members.name 字段
"name" : "supman:28017"增加从节点
rs.add("supman:28018")
{
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1638286626, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1638286626, 1)
}rs.add("supman:28019")
{
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1638286660, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1638286660, 1)
}再次查看状态
{
"set" : "rs0",
"date" : ISODate("2021-11-30T15:44:29.903Z"),
"myState" : 1,
"term" : NumberLong(1),
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"majorityVoteCount" : 2,
"writeMajorityCount" : 2,
"votingMembersCount" : 3,
"writableVotingMembersCount" : 3,
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"lastCommittedWallTime" : ISODate("2021-11-30T15:44:24.673Z"),
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"readConcernMajorityWallTime" : ISODate("2021-11-30T15:44:24.673Z"),
"appliedOpTime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"lastAppliedWallTime" : ISODate("2021-11-30T15:44:24.673Z"),
"lastDurableWallTime" : ISODate("2021-11-30T15:44:24.673Z")
},
"lastStableRecoveryTimestamp" : Timestamp(1638287034, 1),
"electionCandidateMetrics" : {
"lastElectionReason" : "electionTimeout",
"lastElectionDate" : ISODate("2021-11-30T15:27:54.614Z"),
"electionTerm" : NumberLong(1),
"lastCommittedOpTimeAtElection" : {
"ts" : Timestamp(0, 0),
"t" : NumberLong(-1)
},
"lastSeenOpTimeAtElection" : {
"ts" : Timestamp(1638286074, 1),
"t" : NumberLong(-1)
},
"numVotesNeeded" : 1,
"priorityAtElection" : 1,
"electionTimeoutMillis" : NumberLong(10000),
"newTermStartDate" : ISODate("2021-11-30T15:27:54.637Z"),
"wMajorityWriteAvailabilityDate" : ISODate("2021-11-30T15:27:54.660Z")
},
"members" : [
{
"_id" : 0,
"name" : "supman:28017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1886,
"optime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-11-30T15:44:24Z"),
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1638286074, 2),
"electionDate" : ISODate("2021-11-30T15:27:54Z"),
"configVersion" : 3,
"configTerm" : 1,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "supman:28018",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 442,
"optime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-11-30T15:44:24Z"),
"optimeDurableDate" : ISODate("2021-11-30T15:44:24Z"),
"lastHeartbeat" : ISODate("2021-11-30T15:44:28.545Z"),
"lastHeartbeatRecv" : ISODate("2021-11-30T15:44:28.566Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "supman:28017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 3,
"configTerm" : 1
},
{
"_id" : 2,
"name" : "supman:28019",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 409,
"optime" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1638287064, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2021-11-30T15:44:24Z"),
"optimeDurableDate" : ISODate("2021-11-30T15:44:24Z"),
"lastHeartbeat" : ISODate("2021-11-30T15:44:28.565Z"),
"lastHeartbeatRecv" : ISODate("2021-11-30T15:44:29.316Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncSourceHost" : "supman:28018",
"syncSourceId" : 1,
"infoMessage" : "",
"configVersion" : 3,
"configTerm" : 1
}
],
"ok" : 1,
"$clusterTime" : {
"clusterTime" : Timestamp(1638287064, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
},
"operationTime" : Timestamp(1638287064, 1)
}在从节点上配置可读
进入从节点
mongo --port 28018mongo --port 28019
设置从节点可读
rs.slaveOk()
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