（一）MongDB复制（副本集）

MongDB复制是将数据同步到多个服务器的过程。复制提供了数据的冗余备份，并在服务器上存储数据副本，提高数据的可用性，保证数据的安全性，复制允许你从硬件和服务的中断中恢复数据，能随时应对数据丢失、机器损坏带来的风险。而且复制还能提高读取能力，用户读取服务器和写入服务器在不同的地方，提高整个系统的负载。

1、复制的特性：        保障数据的安全性        数据的高可用性7*24        灾难恢复        无需停机维护        分布式读取数据2、复制的原理Mongodb复制集由一组Mongod实例（进程）组成。mongodb复制至少需要二个节点，一个是Primary主节点用于处理客户端的请求，其余都是从节点Secondary用于复制主节点上的数据.Primary会记录那些写的操作到一个日志oplog中，其他的Secondary会定期轮询主节点这个日志，去操作他们的数据库来保持数据库的一致。![](https://s1.51cto.com/107?x-oss-process=image/watermark,size_16,text_QDUxQ1RP5Y2a5a6i,color_FFFFFF,t_100,g_se,x_10,y_10,shadow_90,type_ZmFuZ3poZW5naGVpdGk=)客户端从主节点读取数据，在客户端写入数据到主节点时， 主节点与从节点进行数据交互保障数据的一致性。MongoDB（3.2以上）中，官方已经不推荐使用主从模式，取而代之的，是使用复制集（Replica Set）的方式做主备处理。3、复制集（Replica Set），在复制集中，有且只有一个主节点(primary)，可以包含一个或多个从节点(secondary)，主从节点直接会通过心跳检测来确定节点是否健康或存活。所有的读写操作都是在主节点上进行的，如果要实现读写分离，需要进行相应的处理，这个最后会说。从节点会根据oplog（也就是操作日志）来复制主节点的数据。

原理：而 MongoDB 复制集,集群中的任何节点都可能成为 Master 节点。一旦 Master 节点故障,则会在其余节点中选举出一个新的 Master 节点。 并引导剩余节点连接到新的 Master 节点。这个过程对于应用是透明的。

在生产环境，复制集至少包括三个节点，其中一个必须为主节点，一个从节点，一个仲裁节点。其中每一个节点都是mongod进程对应的实例，节点间通过心跳检查对方的状态。

primary节点：负责数据库的读写操作。secondary节点：备份primary节点上的数据，可以有多个。arbiter节点：主节点故障时，参与复制集剩下节点中选举一个新的primary节点。

（二）、mongodb环境配置

1、主机配置192.168.4.203 db1 ##primary节点192.168.4.97 db2 ##secondary节点192.168.4.200 db3 ##arbriter节点2、安装（略）请参考https://blog.51cto.com/liqingbiao/2401942

3、primary节点的相关操作。           3.1、相关主节点的配置

[root@otrs ~]# vim /usr/local/mongodb/conf/master.conf bind_ip = 0.0.0.0port    = 27017dbpath  = /data/mongodb/dblogpath = /data/mongodb/mongodb.loglogappend = truefork    = truejournal=truemaxConns=1000auth  = truekeyFile = /usr/local/mongodb/mongodb-keyfilestorageEngine=wiredTigeroplogSize=2048replSet=RSkeyFile = /usr/local/mongodb/mongodb-keyfile   ##### 集群的私钥的完整路径，只对于Replica Set 架构有效（noauth = true时不用配置此项）

3.2、在服务器上生成私钥，并设置成600，把该私钥scp到其它远程服务器上。

[root@otrs ~]# openssl rand -base64 745 > /usr/local/mongodb/mongodb-keyfile[root@otrs ~]# chmod 600 /usr/local/mongodb/mongodb-keyfile [root@otrs ~]# cat /usr/local/mongodb/mongodb-keyfile 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[root@otrs ~]# scp /usr/local/mongodb/mongodb-keyfile root@192.168.4.97:/usr/local/mongodb/mongodb-keyfile                                                                               100% 1012     1.0KB/s   00:00

3.3、创建认证用户。由于配置文件启用认证模式，现在需要以非认证的模式来创建用户。

#```#######先以非验证模式启动数据库[root@otrs ~]# /usr/local/mongodb/bin/mongod --fork --dbpath=/data/mongodb/db --logpath=/data/mongodb/mongodb.logabout to fork child process, waiting until server is ready for connections.forked process: 28389child process started successfully, parent exiting[root@otrs ~]# netstat -lntp|grep mongodtcp 0 0 127.0.0.1:27017 0.0.0.0:* LISTEN 28389/mongod ############创建root用户并配置管理员权限[root@otrs ~]# mongoMongoDB shell version v4.0.9connecting to: mongodb://127.0.0.1:27017/?gssapiServiceName=mongodbImplicit session: session { "id" : UUID("4df82588-c03c-49e5-8839-92dafd7ff8ce") }MongoDB server version: 4.0.9Welcome to the MongoDB shell.For interactive help, type "help".For more comprehensive documentation, seeQuestions? Try the support groupServer has startup warnings: 2019-06-14T16:02:56.903+0800 I CONTROL [initandlisten] 2019-06-14T16:02:56.903+0800 I CONTROL [initandlisten] WARNING: Access control is not enabled for the database.

2019-06-14T16:02:56.903+0800 I CONTROL [initandlisten] Read and write access to data and configuration is unrestricted.2019-06-14T16:02:56.903+0800 I CONTROL [initandlisten]

show dbs

admin 0.000GB

config 0.000GB

local 0.000GB

use admin

switched to db admin

db.createUser({ user: "root", pwd: "root", roles: [ { role: "root", db: "admin" } ] });

"user" : "root",

"roles" : [

{

"role" : "root",

"db" : "admin"

}

]

}

3.4、启动以验证权限的配置文件

[root@otrs ~]# mongod --config /usr/local/mongodb/conf/master.conf

about to fork child process, waiting until server is ready for connections.

forked process: 28698

child process started successfully, parent exiting

[root@otrs ~]# ps -ef|grep mongod

root 28698 1 19 16:19 ? 00:00:01 mongod --config /usr/local/mongodb/conf/master.conf

root 28731 28040 0 16:19 pts/0 00:00:00 grep --color=auto mongod

4、配置secondary节点4.1、新建目录编辑配置文件

[root@otrs004097 opt]# mkdir /data/mongodb/standard

[root@otrs004097 opt]# cat /usr/local/mongodb/conf/standard.conf

bind_ip = 0.0.0.0

port = 27017

dbpath = /data/mongodb/standard

logpath = /data/mongodb/mongodb.log

logappend = true

fork = true

journal=true

maxConns=1000

auth = true

keyFile = /usr/local/mongodb/mongodb-keyfile

storageEngine=wiredTiger

oplogSize=2048

replSet=RS

4.2、启动服务

[root@otrs004097 opt]# /usr/local/mongodb/bin/mongod --fork --config /usr/local/mongodb/conf/standard.conf

[root@otrs004097 opt]# netstat -lntp|grep mongod

tcp 0 0 0.0.0.0:27017 0.0.0.0:* LISTEN 1045/mongod

5、配置arbriter节点

[root@NginxServer01 mongodb]# cat /usr/local/mongodb/conf/arbiter.conf

bind_ip = 0.0.0.0

port = 27017

dbpath = /data/mongodb/arbiter

logpath = /data/mongodb/mongodb.log

logappend = true

fork = true

journal=true

maxConns=1000

auth = true

keyFile = /usr/local/mongodb/mongodb-keyfile

storageEngine=wiredTiger

oplogSize=2048

replSet=RS

[root@NginxServer01 mongodb]# /usr/local/mongodb/bin/mongod --config /usr/local/mongodb/conf/arbiter.conf

about to fork child process, waiting until server is ready for connections.

forked process: 26321

child process started successfully, parent exiting

[root@NginxServer01 mongodb]# netstat -lntp|grep mongod

tcp 0 0 0.0.0.0:27017 0.0.0.0:* LISTEN 26321/mongod

6、在primary节点服务器上，初始化复制集primary节点、添加secondary节点和arbriter节点。6.1、初始化primary节点

[root@otrs ~]# mongo -uroot -p

MongoDB shell version v4.0.9

Enter password:

#########查看副本集的状态，发现并未初始化，接下来进行初始化。

rs.status()

{

"ok" : 0,

"errmsg" : "no replset config has been received",

"code" : 94,

"codeName" : "NotYetInitialized"

}

#########进行config的配置

config={"_id":"RS","members":[ {"_id":0,"host":"192.168.4.203:27017"},{"_id":1,"host":"192.168.4.97:27017"}]}

{

"_id" : "RS",

"members" : [

{

"_id" : 0,

"host" : "192.168.4.203:27017"

},

{

"_id" : 1,

"host" : "192.168.4.97:27017"

}

]

}

rs.initiate(config); #######初始化

{ "ok" : 1 }

6.2、查看副本集的状态

RS:SECONDARY> rs.status(){    "set" : "RS",    "date" : ISODate("2019-06-14T09:01:19.722Z"),    "myState" : 2,    "term" : NumberLong(0),    "syncingTo" : "",    "syncSourceHost" : "",    "syncSourceId" : -1,    "heartbeatIntervalMillis" : NumberLong(2000),    "optimes" : {        "lastCommittedOpTime" : {            "ts" : Timestamp(0, 0),            "t" : NumberLong(-1)        },        "appliedOpTime" : {            "ts" : Timestamp(1560502874, 1),            "t" : NumberLong(-1)        },        "durableOpTime" : {            "ts" : Timestamp(1560502874, 1),            "t" : NumberLong(-1)        }    },    "lastStableCheckpointTimestamp" : Timestamp(0, 0),    "members" : [        {            "_id" : 0,            "name" : "192.168.4.203:27017",            "health" : 1,            "state" : 2,            "stateStr" : "SECONDARY",            "uptime" : 2525,            "optime" : {                "ts" : Timestamp(1560502874, 1),                "t" : NumberLong(-1)            },            "optimeDate" : ISODate("2019-06-14T09:01:14Z"),            "syncingTo" : "",            "syncSourceHost" : "",            "syncSourceId" : -1,            "infoMessage" : "could not find member to sync from",            "configVersion" : 1,            "self" : true,            "lastHeartbeatMessage" : ""        },        {            "_id" : 1,            "name" : "192.168.4.97:27017",            "health" : 1,            "state" : 2,            "stateStr" : "SECONDARY",            "uptime" : 5,            "optime" : {                "ts" : Timestamp(1560502874, 1),                "t" : NumberLong(-1)            },            "optimeDurable" : {                "ts" : Timestamp(1560502874, 1),                "t" : NumberLong(-1)            },            "optimeDate" : ISODate("2019-06-14T09:01:14Z"),            "optimeDurableDate" : ISODate("2019-06-14T09:01:14Z"),            "lastHeartbeat" : ISODate("2019-06-14T09:01:19.645Z"),            "lastHeartbeatRecv" : ISODate("2019-06-14T09:01:19.489Z"),            "pingMs" : NumberLong(1),            "lastHeartbeatMessage" : "",            "syncingTo" : "",            "syncSourceHost" : "",            "syncSourceId" : -1,            "infoMessage" : "",            "configVersion" : 1        }    ],    "ok" : 1}

6.3、由初始化结果查看，两个都是secondary节点，由于数据库同步没有完成，等同步完成的时候会变成primary节点。等两分钟再次查看下

RS:PRIMARY> rs.status(){    "set" : "RS",    "date" : ISODate("2019-06-14T09:11:17.382Z"),    "myState" : 1,    "term" : NumberLong(1),    "syncingTo" : "",    "syncSourceHost" : "",    "syncSourceId" : -1,    "heartbeatIntervalMillis" : NumberLong(2000),    "optimes" : {        "lastCommittedOpTime" : {            "ts" : Timestamp(1560503477, 1),            "t" : NumberLong(1)        },        "readConcernMajorityOpTime" : {            "ts" : Timestamp(1560503477, 1),            "t" : NumberLong(1)        },        "appliedOpTime" : {            "ts" : Timestamp(1560503477, 1),            "t" : NumberLong(1)        },        "durableOpTime" : {            "ts" : Timestamp(1560503477, 1),            "t" : NumberLong(1)        }    },    "lastStableCheckpointTimestamp" : Timestamp(1560503427, 1),    "members" : [        {            "_id" : 0,            "name" : "192.168.4.203:27017",            "health" : 1,            "state" : 1,            "stateStr" : "PRIMARY",            "uptime" : 3123,            "optime" : {                "ts" : Timestamp(1560503477, 1),                "t" : NumberLong(1)            },            "optimeDate" : ISODate("2019-06-14T09:11:17Z"),            "syncingTo" : "",            "syncSourceHost" : "",            "syncSourceId" : -1,            "infoMessage" : "",            "electionTime" : Timestamp(1560502885, 1),            "electionDate" : ISODate("2019-06-14T09:01:25Z"),            "configVersion" : 1,            "self" : true,            "lastHeartbeatMessage" : ""        },        {            "_id" : 1,            "name" : "192.168.4.97:27017",            "health" : 1,            "state" : 2,            "stateStr" : "SECONDARY",            "uptime" : 603,            "optime" : {                "ts" : Timestamp(1560503467, 1),                "t" : NumberLong(1)            },            "optimeDurable" : {                "ts" : Timestamp(1560503467, 1),                "t" : NumberLong(1)            },            "optimeDate" : ISODate("2019-06-14T09:11:07Z"),            "optimeDurableDate" : ISODate("2019-06-14T09:11:07Z"),            "lastHeartbeat" : ISODate("2019-06-14T09:11:15.995Z"),            "lastHeartbeatRecv" : ISODate("2019-06-14T09:11:16.418Z"),            "pingMs" : NumberLong(0),            "lastHeartbeatMessage" : "",            "syncingTo" : "192.168.4.203:27017",            "syncSourceHost" : "192.168.4.203:27017",            "syncSourceId" : 0,            "infoMessage" : "",            "configVersion" : 1        }    ],    "ok" : 1,    "operationTime" : Timestamp(1560503477, 1),    "$clusterTime" : {        "clusterTime" : Timestamp(1560503477, 1),        "signature" : {            "hash" : BinData(0,"iR63R/X7QanbrWvuDJNkpdPgcVY="),            "keyId" : NumberLong("6702308864978583553")        }    }}

6.4、在secondary服务器上查看同步日志

[root@otrs004097 opt]# tail  -f /data/mongodb/mongodb.log  2019-06-14T17:01:15.870+0800 I REPL     [replexec-0] This node is 192.168.4.97:27017 in the config2019-06-14T17:01:15.870+0800 I REPL     [replexec-0] transition to STARTUP2 from STARTUP2019-06-14T17:01:15.871+0800 I REPL     [replexec-0] Starting replication storage threads2019-06-14T17:01:15.872+0800 I REPL     [replexec-2] Member 192.168.4.203:27017 is now in state SECONDARY2019-06-14T17:01:15.872+0800 I STORAGE  [replexec-0] createCollection: local.temp_oplog_buffer with generated UUID: 2e5c6683-a67b-4a16-bd9b-8672ee4db9002019-06-14T17:01:15.880+0800 I REPL     [replication-0] Starting initial sync (attempt 1 of 10)2019-06-14T17:01:15.881+0800 I STORAGE  [replication-0] Finishing collection drop for local.temp_oplog_buffer (2e5c6683-a67b-4a16-bd9b-8672ee4db900).2019-06-14T17:01:15.882+0800 I STORAGE  [replication-0] createCollection: local.temp_oplog_buffer with generated UUID: c25fa3cf-cae9-430b-b514-f13c3ab1e2472019-06-14T17:01:15.889+0800 I REPL     [replication-0] sync source candidate: 192.168.4.203:270172019-06-14T17:01:15.889+0800 I REPL     [replication-0] Initial syncer oplog truncation finished in: 0ms2019-06-14T17:01:15.889+0800 I REPL     [replication-0] ******2019-06-14T17:01:15.889+0800 I REPL     [replication-0] creating replication oplog of size: 2048MB...2019-06-14T17:01:15.889+0800 I STORAGE  [replication-0] createCollection: local.oplog.rs with generated UUID: f35caf0a-f2da-4cf7-b16b-34a94f1e25a72019-06-14T17:01:15.892+0800 I STORAGE  [replication-0] Starting OplogTruncaterThread local.oplog.rs2019-06-14T17:01:15.892+0800 I STORAGE  [replication-0] The size storer reports that the oplog conta××× 0 records totaling to 0 bytes2019-06-14T17:01:15.892+0800 I STORAGE  [replication-0] Scanning the oplog to determine where to place markers for truncation2019-06-14T17:01:15.905+0800 I REPL     [replication-0] ******2019-06-14T17:01:15.905+0800 I STORAGE  [replication-0] dropAllDatabasesExceptLocal 1

6.5、添加arbriter仲裁节点

RS:PRIMARY> rs.addArb("192.168.4.45:27017"){"ok" : 1,"operationTime" : Timestamp(1560504144, 1),"$clusterTime" : {"clusterTime" : Timestamp(1560504144, 1),"signature" : {    "hash" : BinData(0,"um2WmD60Gh9q/43qUff8yN2abIw="),    "keyId" : NumberLong("6702308864978583553")}}}

##########查看复制集的状态

RS:PRIMARY> rs.status(){ "set" : "RS","date" : ISODate("2019-06-14T09:40:04.334Z"),"myState" : 1,"term" : NumberLong(1),"syncingTo" : "","syncSourceHost" : "","syncSourceId" : -1,"heartbeatIntervalMillis" : NumberLong(2000),"optimes" : { "lastCommittedOpTime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"readConcernMajorityOpTime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"appliedOpTime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"durableOpTime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)}},"lastStableCheckpointTimestamp" : Timestamp(1560505167, 1),"members" : [{ "_id" : 0,"name" : "192.168.4.203:27017","health" : 1,"state" : 1,"stateStr" : "PRIMARY","uptime" : 4850,"optime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"optimeDate" : ISODate("2019-06-14T09:39:57Z"),"syncingTo" : "","syncSourceHost" : "","syncSourceId" : -1,"infoMessage" : "","electionTime" : Timestamp(1560502885, 1),"electionDate" : ISODate("2019-06-14T09:01:25Z"),"configVersion" : 2,"self" : true,"lastHeartbeatMessage" : ""},{ "_id" : 1,"name" : "192.168.4.97:27017","health" : 1,"state" : 2,"stateStr" : "SECONDARY","uptime" : 2330,"optime" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"optimeDurable" : { "ts" : Timestamp(1560505197, 1),"t" : NumberLong(1)},"optimeDate" : ISODate("2019-06-14T09:39:57Z"),"optimeDurableDate" : ISODate("2019-06-14T09:39:57Z"),"lastHeartbeat" : ISODate("2019-06-14T09:40:02.717Z"),"lastHeartbeatRecv" : ISODate("2019-06-14T09:40:02.767Z"),"pingMs" : NumberLong(0),"lastHeartbeatMessage" : "","syncingTo" : "192.168.4.203:27017","syncSourceHost" : "192.168.4.203:27017","syncSourceId" : 0,"infoMessage" : "","configVersion" : 2},{ "_id" : 2,"name" : "192.168.4.45:27017","health" : 1,"state" : 7,"stateStr" : "ARBITER","uptime" : 11,"lastHeartbeat" : ISODate("2019-06-14T09:40:02.594Z"),"lastHeartbeatRecv" : ISODate("2019-06-14T09:40:04.186Z"),"pingMs" : NumberLong(0),"lastHeartbeatMessage" : "","syncingTo" : "","syncSourceHost" : "","syncSourceId" : -1,"infoMessage" : "","configVersion" : 2}],"ok" : 1,"operationTime" : Timestamp(1560505197, 1),"$clusterTime" : { "clusterTime" : Timestamp(1560505197, 1),"signature" : { "hash" : BinData(0,"Ff00RyXUvxDPc5nzFQYXGZIlnBc="),"keyId" : NumberLong("6702308864978583553")}}}

备注："health" : 1,——————是1，表示健康状态"stateStr" : "PRIMARY",——————主"stateStr" : "SECONDARY",——————从"stateStr" : "ARBITER",——————仲裁

7、查看primary节点、secondary节点、arbriter节点的数据的变化

7.1、主节点Parimary操作，创建表并插入数据。8.RS:PRIMARY> use lqbswitched to db lqbRS:PRIMARY> db.object.×××ert([{"language":"C"},{"language":"C++"}])BulkWriteResult({ "writeErrors" : [ ],"writeConcernErrors" : [ ],"nInserted" : 2,"nUpserted" : 0,"nMatched" : 0,"nModified" : 0,"nRemoved" : 0,"upserted" : [ ]})RS:PRIMARY> db.object.find(){ "_id" : ObjectId("5d0370424e7535b767bb7098"), "language" : "C" }{ "_id" : ObjectId("5d0370424e7535b767bb7099"), "language" : "C++" }

7.2、从节点操作。查看有数据同步到

RS:SECONDARY> use lqb;switched to db lqbRS:SECONDARY> rs.slaveOk();RS:SECONDARY> db.object.find(){ "_id" : ObjectId("5d0370424e7535b767bb7099"), "language" : "C++" }{ "_id" : ObjectId("5d0370424e7535b767bb7098"), "language" : "C" }

7.3、仲裁节点aribriter。仲裁节点不会存储数据

RS:ARBITER> use lqb;switched to db lqbRS:ARBITER> show tablesWarning: unable to run listCollections, attempting to approximate collection names by parsing connectionStatusRS:ARBITER> db.object.find()Error: error: { "ok" : 0,"errmsg" : "not authorized on lqb to execute command { find: \"object\", filter: {}, lsid: { id: UUID(\"d2d7e624-8f30-468a-a3b0-79728b0cabbd\") }, $readPreference: { mode: \"secondaryPreferred\" }, $db: \"lqb\" }","code" : 13,

8、结论：结论一：当主节点挂了得时候，从节点会变成主节点，当原先的主节点恢复的时候，会变成从节点，主节点不变。结论二：主节点能写，从节点不能写。结论三：主从节点的角色换了得话，原先的读写也就换了。