MongoDB 副本集 Replica Sets 搭建

时间  2020-11-26
标签 shell centos 数组 服务器 网络 架构 app 测试 spa 栏目 MongoDB 繁體版
原文   原文链接

MongoDB 副本集 Replica Sets 搭建

一 .三种角色 说明

1. 主要成员（Primary）：主要接收全部写操做。就是主节点。 shell

2. 副本成员（Replicate）：从主节点经过复制操做以维护相同的数据集，即备份数据，不可写操做，但可以读操做（但须要配置）。是默认的一种从节点类型。centos

3.  仲裁者（Arbiter）：不保留任何数据的副本，只具备投票选举做用。固然也能够将仲裁服务器维护为副本集的一部分，即副本成员同时也能够是仲裁者。也是一种从节点类型。数组

关于仲裁者的额外说明：

您能够将额外的mongod实例添加到副本集做为仲裁者。 仲裁者不维护数据集。 仲裁者的目的是经过响应其余副本集成员的心跳和选举请求来维护副本集中的仲裁。 由于它们不存储数据集，因此仲裁器可以是提供副本集仲裁功能的好方法，其资源成本比具备数据集的全功能副本集成员更便宜。 服务器

若是您的副本集具备偶数个成员，请添加仲裁者以得到主要选举中的 “ 大多数 ” 投票。 仲裁者不须要专用 硬件。

 

仲裁者将永远是仲裁者，而主要人员可能会退出并成为次要人员，而次要人员可能成为选举期间的主要人员。 网络

若是你的副本 + 主节点的个数是偶数，建议加一个仲裁者，造成奇数，容易知足大多数的投票。
 
若是你的副本 + 主节点的个数是奇数，能够不加仲裁者

二. 副本集架构目标

一主一副本 一仲裁

1. 建立三个目录 隔离三个配置、数据、日志

myrs_27017  myrs_27018 myrs_27019

[root@VM_0_7_centos mongo]# pwd
/usr/local/mongo
[root@VM_0_7_centos mongo]# ll
total 32
drwxr-xr-x 4 root root 4096 Oct  9 21:20 data
drwxr-xr-x 2 root root 4096 Oct  6 20:30 data28128
drwxr-xr-x 2 root root 4096 Oct  6 20:30 logs
-rw-r--r-- 1 root root  172 Oct  6 20:32 mongo28128.conf
-rw-r--r-- 1 root root  162 Sep 28 22:28 mongo.conf
drwxr-xr-x 4 root root 4096 Oct  9 21:44 myrs_27017
drwxr-xr-x 4 root root 4096 Oct  9 22:05 myrs_27018
drwxr-xr-x 4 root root 4096 Oct  9 21:58 myrs_27019

2. 在每一个目录中建立 如下文件及目录

mongod.conf            配置文件架构

/data/db                    数据目录app

/log/                         日志目录测试

/log/mongod.log      日志文件ui

3. 配置文件内容

以27017 为例，修改 2701八、27019spa

bind_ip=0.0.0.0
#对应端口
port=27017
#数据目录
dbpath=/usr/local/mongo/myrs_27017/data/db
#日志文件
logpath=/usr/local/mongo/myrs_27017/log/mongod.log
logappend=true
journal=true
maxConns=2000
fork=true
#副本集名称
replSet=myrs

4. 启动三个Mongo服务

[root@VM_0_7_centos myrs_27017]# mongod -f /usr/local/mongo/myrs_27017/mongo.conf 
about to fork child process, waiting until server is ready for connections.
forked process: 25929
child process started successfully, parent exiting
[root@VM_0_7_centos myrs_27017]# mongod -f /usr/local/mongo/myrs_27018/mongo.conf 
about to fork child process, waiting until server is ready for connections.
forked process: 26061
child process started successfully, parent exiting
[root@VM_0_7_centos myrs_27017]# mongod -f /usr/local/mongo/myrs_27019/mongo.conf 
about to fork child process, waiting until server is ready for connections.
forked process: 26159
child process started successfully, parent exiting

5. 登陆主机
 

mongo --host 172.21.0.7:27017

6. 使用默认配置初始化副本集

示例：

提示：
1 ） “ok” 的值为 1 ，说明建立成功。
2 ）命令行提示符发生变化，变成了一个从节点角色，此时默认不能读写。稍等片刻，回车，变成主节 点。
 

7. 查看副本集的配置 rs.config()

rs.conf(configuration)   别名 rs.config()
confifiguration ：可选，若是没有配置，则使用默认主节点配置。 .
  
myrs:PRIMARY> rs.config()
{
	"_id" : "myrs",
	"version" : 5,
	"protocolVersion" : NumberLong(1),
	"writeConcernMajorityJournalDefault" : true,
	"members" : [
		{
			"_id" : 0,
			"host" : "VM_0_7_centos:27017",
			"arbiterOnly" : false,
			"buildIndexes" : true,
			"hidden" : false,
			"priority" : 1,
			"tags" : {
				
			},
			"slaveDelay" : NumberLong(0),
			"votes" : 1
		}
	],
	"settings" : {
		"chainingAllowed" : true,
		"heartbeatIntervalMillis" : 2000,
		"heartbeatTimeoutSecs" : 10,
		"electionTimeoutMillis" : 10000,
		"catchUpTimeoutMillis" : -1,
		"catchUpTakeoverDelayMillis" : 30000,
		"getLastErrorModes" : {
			
		},
		"getLastErrorDefaults" : {
			"w" : 1,
			"wtimeout" : 0
		},
		"replicaSetId" : ObjectId("5f806d1896301db3f14d0412")
	}
}

 

本质是查询system.replset表中的数据 
myrs:PRIMARY> use local
switched to db local
myrs:PRIMARY> show collections
oplog.rs
replset.election
replset.minvalid
replset.oplogTruncateAfterPoint
startup_log
system.replset
system.rollback.id
myrs:PRIMARY> db.system.replset.find()
{ "_id" : "myrs", "version" : 5, "protocolVersion" : NumberLong(1), "writeConcernMajorityJournalDefault" : true, "members" : [ { "_id" : 0, "host" : "VM_0_7_centos:27017", "arbiterOnly" : false, "buildIndexes" : true, "hidden" : false, "priority" : 1, "tags" : {  }, "slaveDelay" : NumberLong(0), "votes" : 1 } ], "settings" : { "chainingAllowed" : true, "heartbeatIntervalMillis" : 2000, "heartbeatTimeoutSecs" : 10, "electionTimeoutMillis" : 10000, "catchUpTimeoutMillis" : -1, "catchUpTakeoverDelayMillis" : 30000, "getLastErrorModes" : {  }, "getLastErrorDefaults" : { "w" : 1, "wtimeout" : 0 }, "replicaSetId" : ObjectId("5f806d1896301db3f14d0412") } }

 

 8. 查看副本集的状态 rs.status()

说明 ：

    "set" : "myrs",:副本集的名称

    "myState" : 1,说明状态正常

    "members" : [  副本集成员数组。

myrs:PRIMARY> rs.status()
{
	"set" : "myrs",
	"date" : ISODate("2020-10-10T08:01:46.987Z"),
	"myState" : 1,
	"term" : NumberLong(2),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
	"majorityVoteCount" : 1,
	"writeMajorityCount" : 1,
	"optimes" : {
		"lastCommittedOpTime" : {
			"ts" : Timestamp(1602316900, 1),
			"t" : NumberLong(2)
		},
		"lastCommittedWallTime" : ISODate("2020-10-10T08:01:40.808Z"),
		"readConcernMajorityOpTime" : {
			"ts" : Timestamp(1602316900, 1),
			"t" : NumberLong(2)
		},
		"readConcernMajorityWallTime" : ISODate("2020-10-10T08:01:40.808Z"),
		"appliedOpTime" : {
			"ts" : Timestamp(1602316900, 1),
			"t" : NumberLong(2)
		},
		"durableOpTime" : {
			"ts" : Timestamp(1602316900, 1),
			"t" : NumberLong(2)
		},
		"lastAppliedWallTime" : ISODate("2020-10-10T08:01:40.808Z"),
		"lastDurableWallTime" : ISODate("2020-10-10T08:01:40.808Z")
	},
	"lastStableRecoveryTimestamp" : Timestamp(1602316880, 1),
	"lastStableCheckpointTimestamp" : Timestamp(1602316880, 1),
	"electionCandidateMetrics" : {
		"lastElectionReason" : "electionTimeout",
		"lastElectionDate" : ISODate("2020-10-10T07:41:00.774Z"),
		"electionTerm" : NumberLong(2),
		"lastCommittedOpTimeAtElection" : {
			"ts" : Timestamp(0, 0),
			"t" : NumberLong(-1)
		},
		"lastSeenOpTimeAtElection" : {
			"ts" : Timestamp(1602253127, 1),
			"t" : NumberLong(1)
		},
		"numVotesNeeded" : 2,
		"priorityAtElection" : 1,
		"electionTimeoutMillis" : NumberLong(10000),
		"numCatchUpOps" : NumberLong(0),
		"newTermStartDate" : ISODate("2020-10-10T07:41:00.783Z"),
		"wMajorityWriteAvailabilityDate" : ISODate("2020-10-10T07:41:01.749Z")
	},
	"members" : [
		{
			"_id" : 0,
			"name" : "VM_0_7_centos:27017",
			"health" : 1,
			"state" : 1,
			"stateStr" : "PRIMARY",
			"uptime" : 1281,
			"optime" : {
				"ts" : Timestamp(1602316900, 1),
				"t" : NumberLong(2)
			},
			"optimeDate" : ISODate("2020-10-10T08:01:40Z"),
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"electionTime" : Timestamp(1602315660, 1),
			"electionDate" : ISODate("2020-10-10T07:41:00Z"),
			"configVersion" : 5,
			"self" : true,
			"lastHeartbeatMessage" : ""
		}
	],
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602316900, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602316900, 1)
}
myrs:PRIMARY>

9. 添加 副本从节点

rs.add(host, arbiterOnly)
 
主机成员的配置文档： 
{  
    _id: <int>,
 host: <string>, // required
 arbiterOnly: <boolean>,
 buildIndexes: <boolean>,
 hidden: <boolean>, 
 priority: <number>, 
 tags: <document>, 
 slaveDelay: <int>, 
 votes: <number>
}
将27018的副本节点添加到副本集中： 
myrs:PRIMARY> rs.add("172.21.0.7:27018")
{
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602317234, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602317234, 1)
}

OK：1 说明添加成功

此时查看副本集的状态： 

members中增长了27018  ，其角色是"stateStr" : "SECONDARY",

myrs:PRIMARY> rs.status()
{
	"set" : "myrs",
	"date" : ISODate("2020-10-10T08:08:05.179Z"),
	"myState" : 1,
	"term" : NumberLong(2),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
	"majorityVoteCount" : 2,
	"writeMajorityCount" : 2,
	"optimes" : {
		"lastCommittedOpTime" : {
			"ts" : Timestamp(1602317280, 1),
			"t" : NumberLong(2)
		},
		"lastCommittedWallTime" : ISODate("2020-10-10T08:08:00.815Z"),
		"readConcernMajorityOpTime" : {
			"ts" : Timestamp(1602317280, 1),
			"t" : NumberLong(2)
		},
		"readConcernMajorityWallTime" : ISODate("2020-10-10T08:08:00.815Z"),
		"appliedOpTime" : {
			"ts" : Timestamp(1602317280, 1),
			"t" : NumberLong(2)
		},
		"durableOpTime" : {
			"ts" : Timestamp(1602317280, 1),
			"t" : NumberLong(2)
		},
		"lastAppliedWallTime" : ISODate("2020-10-10T08:08:00.815Z"),
		"lastDurableWallTime" : ISODate("2020-10-10T08:08:00.815Z")
	},
	"lastStableRecoveryTimestamp" : Timestamp(1602317234, 1),
	"lastStableCheckpointTimestamp" : Timestamp(1602317234, 1),
	"electionCandidateMetrics" : {
		"lastElectionReason" : "electionTimeout",
		"lastElectionDate" : ISODate("2020-10-10T07:41:00.774Z"),
		"electionTerm" : NumberLong(2),
		"lastCommittedOpTimeAtElection" : {
			"ts" : Timestamp(0, 0),
			"t" : NumberLong(-1)
		},
		"lastSeenOpTimeAtElection" : {
			"ts" : Timestamp(1602253127, 1),
			"t" : NumberLong(1)
		},
		"numVotesNeeded" : 2,
		"priorityAtElection" : 1,
		"electionTimeoutMillis" : NumberLong(10000),
		"numCatchUpOps" : NumberLong(0),
		"newTermStartDate" : ISODate("2020-10-10T07:41:00.783Z"),
		"wMajorityWriteAvailabilityDate" : ISODate("2020-10-10T07:41:01.749Z")
	},
	"members" : [
		{
			"_id" : 0,
			"name" : "VM_0_7_centos:27017",
			"health" : 1,
			"state" : 1,
			"stateStr" : "PRIMARY",
			"uptime" : 1660,
			"optime" : {
				"ts" : Timestamp(1602317280, 1),
				"t" : NumberLong(2)
			},
			"optimeDate" : ISODate("2020-10-10T08:08:00Z"),
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"electionTime" : Timestamp(1602315660, 1),
			"electionDate" : ISODate("2020-10-10T07:41:00Z"),
			"configVersion" : 6,
			"self" : true,
			"lastHeartbeatMessage" : ""
		},
		{
			"_id" : 1,
			"name" : "172.21.0.7:27018",
			"health" : 1,
			"state" : 2,
			"stateStr" : "SECONDARY",
			"uptime" : 48,
			"optime" : {
				"ts" : Timestamp(1602317280, 1),
				"t" : NumberLong(2)
			},
			"optimeDurable" : {
				"ts" : Timestamp(1602317280, 1),
				"t" : NumberLong(2)
			},
			"optimeDate" : ISODate("2020-10-10T08:08:00Z"),
			"optimeDurableDate" : ISODate("2020-10-10T08:08:00Z"),
			"lastHeartbeat" : ISODate("2020-10-10T08:08:04.632Z"),
			"lastHeartbeatRecv" : ISODate("2020-10-10T08:08:03.633Z"),
			"pingMs" : NumberLong(0),
			"lastHeartbeatMessage" : "",
			"syncingTo" : "VM_0_7_centos:27017",
			"syncSourceHost" : "VM_0_7_centos:27017",
			"syncSourceId" : 0,
			"infoMessage" : "",
			"configVersion" : 6
		}
	],
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602317280, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602317280, 1)
}

10.添加仲裁从节点

添加仲裁节点到副本集

rs.addArb(host)

将27019以仲裁节点添加到副本集中

myrs:PRIMARY> rs.addArb("172.21.0.7:27019")
{
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602317560, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602317560, 1)
}

此时查看副本集状态

myrs:PRIMARY> rs.status()
{
	"set" : "myrs",
	"date" : ISODate("2020-10-10T08:13:09.745Z"),
	"myState" : 1,
	"term" : NumberLong(2),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
	"majorityVoteCount" : 2,
	"writeMajorityCount" : 2,
	"optimes" : {
		"lastCommittedOpTime" : {
			"ts" : Timestamp(1602317580, 1),
			"t" : NumberLong(2)
		},
		"lastCommittedWallTime" : ISODate("2020-10-10T08:13:00.821Z"),
		"readConcernMajorityOpTime" : {
			"ts" : Timestamp(1602317580, 1),
			"t" : NumberLong(2)
		},
		"readConcernMajorityWallTime" : ISODate("2020-10-10T08:13:00.821Z"),
		"appliedOpTime" : {
			"ts" : Timestamp(1602317580, 1),
			"t" : NumberLong(2)
		},
		"durableOpTime" : {
			"ts" : Timestamp(1602317580, 1),
			"t" : NumberLong(2)
		},
		"lastAppliedWallTime" : ISODate("2020-10-10T08:13:00.821Z"),
		"lastDurableWallTime" : ISODate("2020-10-10T08:13:00.821Z")
	},
	"lastStableRecoveryTimestamp" : Timestamp(1602317540, 1),
	"lastStableCheckpointTimestamp" : Timestamp(1602317540, 1),
	"electionCandidateMetrics" : {
		"lastElectionReason" : "electionTimeout",
		"lastElectionDate" : ISODate("2020-10-10T07:41:00.774Z"),
		"electionTerm" : NumberLong(2),
		"lastCommittedOpTimeAtElection" : {
			"ts" : Timestamp(0, 0),
			"t" : NumberLong(-1)
		},
		"lastSeenOpTimeAtElection" : {
			"ts" : Timestamp(1602253127, 1),
			"t" : NumberLong(1)
		},
		"numVotesNeeded" : 2,
		"priorityAtElection" : 1,
		"electionTimeoutMillis" : NumberLong(10000),
		"numCatchUpOps" : NumberLong(0),
		"newTermStartDate" : ISODate("2020-10-10T07:41:00.783Z"),
		"wMajorityWriteAvailabilityDate" : ISODate("2020-10-10T07:41:01.749Z")
	},
	"members" : [
		{
			"_id" : 0,
			"name" : "VM_0_7_centos:27017",
			"health" : 1,
			"state" : 1,
			"stateStr" : "PRIMARY",
			"uptime" : 1964,
			"optime" : {
				"ts" : Timestamp(1602317580, 1),
				"t" : NumberLong(2)
			},
			"optimeDate" : ISODate("2020-10-10T08:13:00Z"),
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"electionTime" : Timestamp(1602315660, 1),
			"electionDate" : ISODate("2020-10-10T07:41:00Z"),
			"configVersion" : 7,
			"self" : true,
			"lastHeartbeatMessage" : ""
		},
		{
			"_id" : 1,
			"name" : "172.21.0.7:27018",
			"health" : 1,
			"state" : 2,
			"stateStr" : "SECONDARY",
			"uptime" : 353,
			"optime" : {
				"ts" : Timestamp(1602317580, 1),
				"t" : NumberLong(2)
			},
			"optimeDurable" : {
				"ts" : Timestamp(1602317580, 1),
				"t" : NumberLong(2)
			},
			"optimeDate" : ISODate("2020-10-10T08:13:00Z"),
			"optimeDurableDate" : ISODate("2020-10-10T08:13:00Z"),
			"lastHeartbeat" : ISODate("2020-10-10T08:13:08.288Z"),
			"lastHeartbeatRecv" : ISODate("2020-10-10T08:13:08.292Z"),
			"pingMs" : NumberLong(0),
			"lastHeartbeatMessage" : "",
			"syncingTo" : "VM_0_7_centos:27017",
			"syncSourceHost" : "VM_0_7_centos:27017",
			"syncSourceId" : 0,
			"infoMessage" : "",
			"configVersion" : 7
		},
		{
			"_id" : 2,
			"name" : "172.21.0.7:27019",
			"health" : 1,
			"state" : 7,
			"stateStr" : "ARBITER",
			"uptime" : 27,
			"lastHeartbeat" : ISODate("2020-10-10T08:13:08.290Z"),
			"lastHeartbeatRecv" : ISODate("2020-10-10T08:13:08.293Z"),
			"pingMs" : NumberLong(0),
			"lastHeartbeatMessage" : "",
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"configVersion" : 7
		}
	],
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602317580, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602317580, 1)
}
myrs:PRIMARY>

说明

            "name" : "172.21.0.7:27019", 名称
            "health" : 1,         健康
            "state" : 7,
            "stateStr" : "ARBITER",  状态是仲裁者

11 . 副本集的数据读写操做

11.1 主节点写入数据

myrs:PRIMARY> show dbs
admin      0.000GB
articledb  0.000GB
config     0.000GB
local      0.000GB
myrs:PRIMARY> use articledb
switched to db articledb
myrs:PRIMARY> db.content.insert({title:'AAA',content:'BBB'})
WriteResult({ "nInserted" : 1 })
myrs:PRIMARY> db.content.find()
{ "_id" : ObjectId("5f817a179595bc6e7dfc444c"), "title" : "AAA", "content" : "BBB" }
myrs:PRIMARY>

11.2 副节点尝试读数据

myrs:SECONDARY> show dbs
2020-10-10T17:10:01.034+0800 E  QUERY    [js] uncaught exception: Error: listDatabases failed:{
	"operationTime" : Timestamp(1602321000, 1),
	"ok" : 0,
	"errmsg" : "not master and slaveOk=false",
	"code" : 13435,
	"codeName" : "NotMasterNoSlaveOk",
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602321000, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	}
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
Mongo.prototype.getDBs/<@src/mongo/shell/mongo.js:135:19
Mongo.prototype.getDBs@src/mongo/shell/mongo.js:87:12
shellHelper.show@src/mongo/shell/utils.js:906:13
shellHelper@src/mongo/shell/utils.js:790:15
@(shellhelp2):1:1
myrs:SECONDARY>

发现，不能读取集合的数据。当前从节点只是一个备份，不是奴隶节点，没法读取数据，写固然更不行。由于默认状况下，从节点是没有读写权限的，能够增长读的权限，但须要进行设置

11.3 副节点设置 与 取消 读操做权限

rs.slaveOk()  
或 
rs.slaveOk(true)

设置为奴隶节点，容许在从成员上运行读的操做

myrs:SECONDARY> rs.slaveOk(true)
myrs:SECONDARY> show dbs
admin      0.000GB
articledb  0.000GB
config     0.000GB
local      0.000GB
myrs:SECONDARY> use articledb
switched to db articledb
myrs:SECONDARY> db.content.find()
{ "_id" : ObjectId("5f817a179595bc6e7dfc444c"), "title" : "AAA", "content" : "BBB" }
myrs:SECONDARY>

如今可实现了读写分离，让主插入数据，让历来读取数据。
若是要取消做为奴隶节点的读权限：

myrs:SECONDARY> rs.slaveOk(false)
myrs:SECONDARY> show dbs
2020-10-10T17:14:34.613+0800 E  QUERY    [js] uncaught exception: Error: listDatabases failed:{
	"operationTime" : Timestamp(1602321270, 1),
	"ok" : 0,
	"errmsg" : "not master and slaveOk=false",
	"code" : 13435,
	"codeName" : "NotMasterNoSlaveOk",
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602321270, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	}
} :
_getErrorWithCode@src/mongo/shell/utils.js:25:13
Mongo.prototype.getDBs/<@src/mongo/shell/mongo.js:135:19
Mongo.prototype.getDBs@src/mongo/shell/mongo.js:87:12
shellHelper.show@src/mongo/shell/utils.js:906:13
shellHelper@src/mongo/shell/utils.js:790:15
@(shellhelp2):1:1
myrs:SECONDARY> rs.slaveOk(true)

冲裁者 节点，不存听任何业务数据的，能够登陆查看

先配置为奴隶节点赋予读权限，再查看数据。

myrs:ARBITER> rs.slaveOk()
myrs:ARBITER> show dbs
local  0.000GB
myrs:ARBITER> use local
switched to db local
myrs:ARBITER> show collections
replset.election
replset.minvalid
replset.oplogTruncateAfterPoint
startup_log
system.replset
system.rollback.id
myrs:ARBITER>

12 . 主节点的选举原则


MongoDB在副本集中，会自动进行主节点的选举，主节点选举的触发条件：
1） 主节点故障
2） 主节点网络不可达（默认心跳信息为10秒）
3） 人工干预（rs.stepDown(600)）

一旦触发选举，就要根据必定规则来选主节点。
选举规则是根据票数来决定谁获胜：

  • 票数最高，且得到了“大多数”成员的投票支持的节点获胜。

    “大多数”的定义为：假设复制集内投票成员数量为N，则大多数为 N/2 + 1。例如：3个投票成员，则大多数的值是2。当复制集内存活成员数量不足大多数时，整个复制集将没法选举出Primary，
    复制集将没法提供写服务，处于只读状态。

  • 若票数相同，且都得到了“大多数”成员的投票支持的，数据新的节点获胜。

    数据的新旧是经过操做日志oplog来对比的。

在得到票数的时候，优先级（priority）参数影响重大。能够经过设置优先级（priority）来设置额外票数。优先级即权重，取值为0-1000，至关于可额外增长 0-1000的票数，优先级的值越大，就越可能得到多数成员的投票（votes）数。指定较高的值可以使成员 更有资格成为主要成员，更低的值可以使成员更不符合条件。


默认状况下，优先级的值是1

经过rs.conf()命令查看每一个members中的优先级字段 prioriry 

myrs:ARBITER> rs.conf()
{
	"_id" : "myrs",
	"version" : 7,
	"protocolVersion" : NumberLong(1),
	"writeConcernMajorityJournalDefault" : true,
	"members" : [
		{
			"_id" : 0,
			"host" : "VM_0_7_centos:27017",
			"arbiterOnly" : false,
			"buildIndexes" : true,
			"hidden" : false,
			"priority" : 1,
			"tags" : {
				
			},
			"slaveDelay" : NumberLong(0),
			"votes" : 1
		},
		{
			"_id" : 1,
			"host" : "172.21.0.7:27018",
			"arbiterOnly" : false,
			"buildIndexes" : true,
			"hidden" : false,
			"priority" : 1,
			"tags" : {
				
			},
			"slaveDelay" : NumberLong(0),
			"votes" : 1
		},
		{
			"_id" : 2,
			"host" : "172.21.0.7:27019",
			"arbiterOnly" : true,
			"buildIndexes" : true,
			"hidden" : false,
			"priority" : 0,
			"tags" : {
				
			},
			"slaveDelay" : NumberLong(0),
			"votes" : 1
		}
	],
	"settings" : {
		"chainingAllowed" : true,
		"heartbeatIntervalMillis" : 2000,
		"heartbeatTimeoutSecs" : 10,
		"electionTimeoutMillis" : 10000,
		"catchUpTimeoutMillis" : -1,
		"catchUpTakeoverDelayMillis" : 30000,
		"getLastErrorModes" : {
			
		},
		"getLastErrorDefaults" : {
			"w" : 1,
			"wtimeout" : 0
		},
		"replicaSetId" : ObjectId("5f806d1896301db3f14d0412")
	}
}


能够看出，主节点和副本节点的优先级各为1，即，默承认以认为都已经有了一票。但选举节点，优先级是0，（要注意是,官方说了，选举节点的优先级必须是0，不能是别的值。即不具有选举权，但具备投票权）

修改优先级方法：

1）先将配置导入cfg变量

myrs:SECONDARY> cfg=rs.conf()


2）而后修改值（ID号默认从0开始）：

myrs:SECONDARY> cfg.members[1].priority=2
2


3）从新加载配置  须要在主机操做。
myrs:SECONDARY> rs.reconfig(cfg) 
稍等片刻会从新开始选举。

13. 故障测试

13.1 副本节点故障测试

关闭27018副本节点：

使用127.0.0.1:27018登陆， 不然提示

"errmsg" : "shutdown must run from localhost when running db without auth",

 

[root@VM_0_7_centos ~]# mongo --host 127.0.0.1:27018
....

myrs:SECONDARY> use admin 
switched to db admin
myrs:SECONDARY> db.shutdownServer()


发现，主节点和仲裁节点对27018的心跳失败。由于主节点还在，所以，没有触发投票选举。
若是此时，在主节点写入数据。

myrs:PRIMARY> db.content.insert({title:'CCC',content:'DDD'})
WriteResult({ "nInserted" : 1 })

重启 副节点，配置读权限，再进行读数据

myrs:SECONDARY> rs.slaveOk()
myrs:SECONDARY> show dbs
admin      0.000GB
articledb  0.000GB
config     0.000GB
local      0.000GB
myrs:SECONDARY> use articledb
switched to db articledb
myrs:SECONDARY> db.content.find()
{ "_id" : ObjectId("5f817a179595bc6e7dfc444c"), "title" : "AAA", "content" : "BBB" }
{ "_id" : ObjectId("5f8180369595bc6e7dfc444d"), "title" : "CCC", "content" : "DDD" }
myrs:SECONDARY>

数据已经同步过来了

13.2 主节点故障测试

关闭27017节点
发现，从节点和仲裁节点对27017的心跳失败，当失败超过10秒，此时由于没有主节点了，会自动发起
投票。
而副本节点只有27018，所以，候选人只有一个就是27018，开始投票。
27019向27018投了一票，27018自己自带一票，所以共两票，超过了“大多数”
27019是仲裁节点，没有选举权，27018不向其投票，其票数是0.
最终结果，27018成为主节点。具有读写功能。
在27018写入数据查看。

主节点关闭，再启动，使用27018查看状态

myrs:SECONDARY> rs.status()
{
	"set" : "myrs",
	"date" : ISODate("2020-10-10T09:40:44.700Z"),
	"myState" : 1,
	"term" : NumberLong(3),
	"syncingTo" : "",
	"syncSourceHost" : "",
	"syncSourceId" : -1,
	"heartbeatIntervalMillis" : NumberLong(2000),
	"majorityVoteCount" : 2,
	"writeMajorityCount" : 2,
	"optimes" : {
		"lastCommittedOpTime" : {
			"ts" : Timestamp(1602322836, 1),
			"t" : NumberLong(3)
		},
		"lastCommittedWallTime" : ISODate("2020-10-10T09:40:36.790Z"),
		"readConcernMajorityOpTime" : {
			"ts" : Timestamp(1602322836, 1),
			"t" : NumberLong(3)
		},
		"readConcernMajorityWallTime" : ISODate("2020-10-10T09:40:36.790Z"),
		"appliedOpTime" : {
			"ts" : Timestamp(1602322836, 1),
			"t" : NumberLong(3)
		},
		"durableOpTime" : {
			"ts" : Timestamp(1602322836, 1),
			"t" : NumberLong(3)
		},
		"lastAppliedWallTime" : ISODate("2020-10-10T09:40:36.790Z"),
		"lastDurableWallTime" : ISODate("2020-10-10T09:40:36.790Z")
	},
	"lastStableRecoveryTimestamp" : Timestamp(1602322780, 1),
	"lastStableCheckpointTimestamp" : Timestamp(1602322780, 1),
	"electionCandidateMetrics" : {
		"lastElectionReason" : "stepUpRequestSkipDryRun",
		"lastElectionDate" : ISODate("2020-10-10T09:39:46.784Z"),
		"electionTerm" : NumberLong(3),
		"lastCommittedOpTimeAtElection" : {
			"ts" : Timestamp(1602322780, 1),
			"t" : NumberLong(2)
		},
		"lastSeenOpTimeAtElection" : {
			"ts" : Timestamp(1602322780, 1),
			"t" : NumberLong(2)
		},
		"numVotesNeeded" : 2,
		"priorityAtElection" : 1,
		"electionTimeoutMillis" : NumberLong(10000),
		"priorPrimaryMemberId" : 0,
		"numCatchUpOps" : NumberLong(0),
		"newTermStartDate" : ISODate("2020-10-10T09:39:46.789Z"),
		"wMajorityWriteAvailabilityDate" : ISODate("2020-10-10T09:40:24.592Z")
	},
	"members" : [
		{
			"_id" : 0,
			"name" : "VM_0_7_centos:27017",
			"health" : 1,
			"state" : 2,
			"stateStr" : "SECONDARY",
			"uptime" : 19,
			"optime" : {
				"ts" : Timestamp(1602322836, 1),
				"t" : NumberLong(3)
			},
			"optimeDurable" : {
				"ts" : Timestamp(1602322836, 1),
				"t" : NumberLong(3)
			},
			"optimeDate" : ISODate("2020-10-10T09:40:36Z"),
			"optimeDurableDate" : ISODate("2020-10-10T09:40:36Z"),
			"lastHeartbeat" : ISODate("2020-10-10T09:40:42.792Z"),
			"lastHeartbeatRecv" : ISODate("2020-10-10T09:40:43.086Z"),
			"pingMs" : NumberLong(0),
			"lastHeartbeatMessage" : "",
			"syncingTo" : "172.21.0.7:27018",
			"syncSourceHost" : "172.21.0.7:27018",
			"syncSourceId" : 1,
			"infoMessage" : "",
			"configVersion" : 7
		},
		{
			"_id" : 1,
			"name" : "172.21.0.7:27018",
			"health" : 1,
			"state" : 1,
			"stateStr" : "PRIMARY",
			"uptime" : 297,
			"optime" : {
				"ts" : Timestamp(1602322836, 1),
				"t" : NumberLong(3)
			},
			"optimeDate" : ISODate("2020-10-10T09:40:36Z"),
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"electionTime" : Timestamp(1602322786, 1),
			"electionDate" : ISODate("2020-10-10T09:39:46Z"),
			"configVersion" : 7,
			"self" : true,
			"lastHeartbeatMessage" : ""
		},
		{
			"_id" : 2,
			"name" : "172.21.0.7:27019",
			"health" : 1,
			"state" : 7,
			"stateStr" : "ARBITER",
			"uptime" : 295,
			"lastHeartbeat" : ISODate("2020-10-10T09:40:42.788Z"),
			"lastHeartbeatRecv" : ISODate("2020-10-10T09:40:44.303Z"),
			"pingMs" : NumberLong(0),
			"lastHeartbeatMessage" : "",
			"syncingTo" : "",
			"syncSourceHost" : "",
			"syncSourceId" : -1,
			"infoMessage" : "",
			"configVersion" : 7
		}
	],
	"ok" : 1,
	"$clusterTime" : {
		"clusterTime" : Timestamp(1602322836, 1),
		"signature" : {
			"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
			"keyId" : NumberLong(0)
		}
	},
	"operationTime" : Timestamp(1602322836, 1)
}
myrs:PRIMARY>

27018 变为主节点，写入数据，在27017 上读取

myrs:PRIMARY> show dbs
admin      0.000GB
articledb  0.000GB
config     0.000GB
local      0.000GB
myrs:PRIMARY> use articledb
switched to db articledb
myrs:PRIMARY> show collections
comment
content
myrs:PRIMARY> db.content.insert({"k1":'v1'})
WriteResult({ "nInserted" : 1 })
myrs:PRIMARY>
myrs:SECONDARY> rs.slaveOk()
myrs:SECONDARY> show dbs
admin      0.000GB
articledb  0.000GB
config     0.000GB
local      0.000GB
myrs:SECONDARY> use articledb
switched to db articledb
myrs:SECONDARY> db.content.find()
{ "_id" : ObjectId("5f817a179595bc6e7dfc444c"), "title" : "AAA", "content" : "BBB" }
{ "_id" : ObjectId("5f8180369595bc6e7dfc444d"), "title" : "CCC", "content" : "DDD" }
{ "_id" : ObjectId("5f818206997162c565e0d7ff"), "k1" : "v1" }
myrs:SECONDARY>


13.3 仲裁节点和主节点故障 


先关掉仲裁节点27019，
关掉如今的主节点27018
登陆27017后，发现，27017仍然是从节点，副本集中没有主节点了，致使此时，副本集是只读状态，
没法写入。
为啥不选举了？由于27017的票数，没有得到大多数，即没有大于等于2，它只有默认的一票（优先级
是1）
若是要触发选举，随便加入一个成员便可。

若是只加入27019仲裁节点成员，则主节点必定是27017，由于没得选了，仲裁节点不参与选举，
但参与投票。（不演示）
若是只加入27018节点，会发起选举。由于27017和27018都是两票，则按照谁数据新，谁当主节
点


13.4 仲裁节点和从节点故障  

先关掉仲裁节点27019， 关掉如今的副本节点27018 10秒后，27017主节点自动降级为副本节点。（服务降级） 副本集不可写数据了，已经故障了。

相关文章
相关标签/搜索
每日一句
    每一个你不满意的现在，都有一个你没有努力的曾经。
本站公众号
   欢迎关注本站公众号,获取更多信息
联系我们 最近搜索 最新文章 沪ICP备13005482号-10 MyBatis教程 SQL 教程 MySQL教程 Java 教程 Thymeleaf 教程 Hibernate教程 Spring教程 Redis教程