本文详细介绍了如何在MongoDB 4.x版本中搭建副本集(replica-set)，包括环境准备、配置文件修改、服务启动及主从节点选举过程，并通过实例演示了数据同步验证。
mongodb 主从复制
MongoDB 是一个基于分布式文件存储的数据库。由 C++ 语言编写。旨在为 WEB 应用提供可扩展的高性能数据存储解决方案。
MongoDB 是一个介于关系数据库和非关系数据库之间的产品，是非关系数据库当中功能最丰富，最像关系数据库的。
官方配置说明：https://docs.mongodb.com/manual/reference/configuration-options/#configuration-file
MongoDB的4.x版本已经不再支持主从复制，而是使用副本集(replica-set)。
环境准备：
| ip | hostname | status |
|---|---|---|
| 192.168.20.3 | node2003 | primary |
| 192.168.20.4 | node2004 | secondary |
node2003:
~]# cd /usr/local/pkg/
~]# tar xf mongodb-linux-x86_64-rhel70-4.0.5.tgz
~]# mv mongodb-linux-x86_64-rhel70-4.0.5 mongodb
~]# vim /etc/profile.d/mongodb.sh
export PATH=/usr/loca/pkg/mongodb/bin:$PATH
~]# source /etc/profile.d/mongodb.sh
~]# mkdir {conf.d,data,logs}
~]# vim /usr/local/pkg/mongodb/conf.d/mongodb.conf
systemLog:
destination: file
#发送所有日志输出的目标。指定file或syslog,如果指定file,则必须指定systemLog.path
logAppend: false
#设置为true时，将新条目添加到现有日志文件的末尾。如果设置为false,将备份现有日志并创建新文件。默认为false
logRotate: rename
#renme:重命名旧日志文件，创建新日志文件记录
#reopen:重新将日志追加进旧日志，需logAppend设置为true
path: /usr/local/pkg/mongodb/logs/mongod.log
#日志文件路径
# Where and how to store data.
storage:
dbPath: /usr/local/pkg/mongodb/data
#数据库存储路径
journal:
enabled: true
#默认值：64位系统上为true,32位系统上为false。启用持久性日志以确保数据文件保持有效和可恢复。不支持使用内存存储引擎的实例。
# how the process runs
processManagement:
fork: true # fork and run in background
#后台运行
pidFilePath: /var/run/mongodb/mongod.pid
#pid文件路径
timeZoneInfo: /usr/share/zoneinfo
#加载时区数据库的完整路径。如果未提供此选项，则mongodb将使用其内置时区数据库
# network interfaces
net:
port: 27017
#监听TCP端口
bindIp: node2003
#绑定主机名或IP地址或完整的Unix域套接字路径。要绑定多个地址，用逗号分隔
ssl.mode: disabled
#启用或禁用用于所有网络连接的TLS/SSL或混合TLS/SSL。有如下参数
#disable:服务器不使用TLS/SSL
#allowSSL:服务器之间的连接不使用TLS/SSL。对于连入的连接，服务器接受TLS/SSL和非TLS/SSL
#preferSSL:服务器之间的连接使用TLS/SSL。对于连入的连接，服务器接受TLS/SSL和非TLS/SSL
#requireSSL:服务器仅使用和接受TLS/SSL加密连接
#replication复制集
replication:
oplogSizeMB: 2048
#复制操作日志的最大大小(MB为单位)。
#主节点的操作记录成为oplog(operation log),oplog存储在特殊的数据local中。oplog只是作为从节点与主节点保持数据同步的机制
replSetName: mymon
#4.x版本使用副本集代替主从复制。副本集中的所有主机必具有相同的集名称。启动服务
~]# mongod -f conf.d/mongodb.conf
~]# tail -f logs/mongod.log
2018-12-27T16:28:31.184+0800 I CONTROL [initandlisten]
2018-12-27T16:28:31.184+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is 'always'.
2018-12-27T16:28:31.184+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2018-12-27T16:28:31.184+0800 I CONTROL [initandlisten]
2018-12-27T16:28:31.185+0800 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2018-12-27T16:28:31.185+0800 I CONTROL [initandlisten] ** We suggest setting it to 'never'
2018-12-27T16:28:31.185+0800 I CONTROL [initandlisten]
2018-12-27T16:28:31.196+0800 I FTDC [initandlisten] Initializing full-time diagnostic data capture with directory '/usr/local/pkg/mongodb/data/diagnostic.data'
2018-12-27T16:28:31.197+0800 I NETWORK [initandlisten] waiting for connections on port 27017
2018-12-27T16:28:32.023+0800 I FTDC [ftdc] Unclean full-time diagnostic data capture shutdown detected, found interim file, some metrics may have been lost. OK
有两处警告，需要处理禁用hugepage:
自CentOS6版本开始引入了Transparent Huge Pages(THP)，从CentOS7版本开始，该特性默认就会启用。尽管THP的本意是为提升内存的性能，不过某些数据库厂商还是建议直接关闭THP(比如说Oracle、MariaDB、MongoDB等)，否则可能会导致性能出现下降。
临时关闭(重启服务生效)：
echo never >> /sys/kernel/mm/transparent_hugepage/enabled
echo never >> /sys/kernel/mm/transparent_hugepage/defrag永久关闭(重启机器生效)：
~]# cat /etc/rc.d/rc.local
if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
echo never > /sys/kernel/mm/transparent_hugepage/enabled
fi
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
echo never > /sys/kernel/mm/transparent_hugepage/defrag
finode2004:
~]# cd /usr/local/pkg/
~]# tar xf mongodb-linux-x86_64-rhel70-4.0.5.tgz
~]# mv mongodb-linux-x86_64-rhel70-4.0.5 mongodb
~]# vim /etc/profile.d/mongodb.sh
export PATH=/usr/loca/pkg/mongodb/bin:$PATH
~]# source /etc/profile.d/mongodb.sh
~]# vim mongodb/conf.d/mongodb.conf
systemLog:
destination: file
logAppend: false
logRotate: rename
path: /usr/local/pkg/mongodb/logs/mongod.log
# Where and how to store data.
storage:
dbPath: /usr/local/pkg/mongodb/data
journal:
enabled: true
# how the process runs
processManagement:
fork: true
pidFilePath: /var/run/mongodb/mongod.pid
timeZoneInfo: /usr/share/zoneinfo
# network interfaces
net:
port: 27017
bindIp: node2004
#node2004机器
ssl.mode: disabled
replication:
oplogSizeMB: 2048
replSetName: mymon
关闭hugepage后启动服务
~]# mongod -f mongodb/conf.d/mongodb.conf
about to fork child process, waiting until server is ready for connections.
forked process: 18275
child process started successfully, parent exiting //启动成功node2003:
~]# mongo node2003:27071
MongoDB shell version v4.0.5
connecting to: mongodb://node2003:27017/test?gssapiServiceName=mongodb
Implicit session: session { "id" : UUID("4d6ec81a-957a-4a43-a0b6-0d80d5aa5536") }
MongoDB server version: 4.0.5
Server has startup warnings:
2018-12-27T17:24:04.568+0800 I CONTROL [initandlisten]
2018-12-27T17:24:04.568+0800 I CONTROL [initandlisten] ** WARNING: Access control is not enabled for the database.
2018-12-27T17:24:04.568+0800 I CONTROL [initandlisten] ** Read and write access to data and configuration is unrestricted. //读写不受限制
2018-12-27T17:24:04.568+0800 I CONTROL [initandlisten] ** WARNING: You are running this process as the root user, which is not recommended. //正常还是别用root帐号起服务
2018-12-27T17:24:04.568+0800 I CONTROL [initandlisten]
---
Enable MongoDB's free cloud-based monitoring service, which will then receive and display
metrics about your deployment (disk utilization, CPU, operation statistics, etc).
The monitoring data will be available on a MongoDB website with a unique URL accessible to you
and anyone you share the URL with. MongoDB may use this information to make product
improvements and to suggest MongoDB products and deployment options to you.
To enable free monitoring, run the following command: db.enableFreeMonitoring()
To permanently disable this reminder, run the following command: db.disableFreeMonitoring()
--
>
//定义一个配置对象
> config={_id:"mymon", members:[{_id:0,host:"node2003:27017",priority:1}]}
{
"_id" : "mymon",
#副本名称
"members" : [
{
"_id" : 0,
"host" : "node2003:27017",
"priority" : 1
#优先级，数字越小，优先级越大。就会被优先选举成primary节点
}
]
}
//调用rs API初始化set
> rs.initiate(config)
{
"ok" : 1,
"operationTime" : Timestamp(1545903526, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1545903526, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
mymon:SECONDARY>
//登陆提示符已经显示出来了,但不是primary节点，应该是节点还没选举完成。重新查看一下本机的配置
mymon:SECONDARY> rs.conf()
{
"_id" : "mymon",
"version" : 1,
"protocolVersion" : NumberLong(1),
"writeConcernMajorityJournalDefault" : true,
"members" : [
{
"_id" : 0,
"host" : "node2003:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
}
],
"settings" : {
"chainingAllowed" : true,
"heartbeatIntervalMillis" : 2000,
"heartbeatTimeoutSecs" : 10,
"electionTimeoutMillis" : 10000,
"catchUpTimeoutMillis" : -1,
"catchUpTakeoverDelayMillis" : 30000,
"getLastErrorModes" : {
},
"getLastErrorDefaults" : {
"w" : 1,
"wtimeout" : 0
},
"replicaSetId" : ObjectId("5c249da69445df4a35b62059")
}
}
mymon:PRIMARY>
//primary节点已经选举成功了然后我们将node2004节点添加进来：
mymon:PRIMARY> rs.add("node2004:27017")
{
"ok" : 1,
"operationTime" : Timestamp(1545903657, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1545903657, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
//查看状态
mymon:PRIMARY> rs.status()
{
"set" : "mymon",
"date" : ISODate("2018-12-27T09:41:12.487Z"),
"myState" : 1,
"term" : NumberLong(1),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"heartbeatIntervalMillis" : NumberLong(2000),
"optimes" : {
"lastCommittedOpTime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"readConcernMajorityOpTime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"appliedOpTime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"durableOpTime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
}
},
"lastStableCheckpointTimestamp" : Timestamp(1545903638, 1),
"members" : [
{
"_id" : 0,
"name" : "node2003:27017",
"health" : 1,
"state" : 1,
"stateStr" : "PRIMARY",
"uptime" : 1579,
"optime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2018-12-27T09:41:08Z"),
"syncingTo" : "",
"syncSourceHost" : "",
"syncSourceId" : -1,
"infoMessage" : "",
"electionTime" : Timestamp(1545903526, 2),
"electionDate" : ISODate("2018-12-27T09:38:46Z"),
"configVersion" : 2,
"self" : true,
"lastHeartbeatMessage" : ""
},
{
"_id" : 1,
"name" : "node2004:27017",
"health" : 1,
"state" : 2,
"stateStr" : "SECONDARY",
"uptime" : 15,
"optime" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"optimeDurable" : {
"ts" : Timestamp(1545903668, 1),
"t" : NumberLong(1)
},
"optimeDate" : ISODate("2018-12-27T09:41:08Z"),
"optimeDurableDate" : ISODate("2018-12-27T09:41:08Z"),
"lastHeartbeat" : ISODate("2018-12-27T09:41:11.029Z"),
"lastHeartbeatRecv" : ISODate("2018-12-27T09:41:11.583Z"),
"pingMs" : NumberLong(0),
"lastHeartbeatMessage" : "",
"syncingTo" : "node2003:27017",
"syncSourceHost" : "node2003:27017",
"syncSourceId" : 0,
"infoMessage" : "",
"configVersion" : 2
}
],
"ok" : 1,
"operationTime" : Timestamp(1545903668, 1),
"$clusterTime" : {
"clusterTime" : Timestamp(1545903668, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}可以看到节点已经添加进mymon副本集里了。
增加数据测试副本是否成功：
mymon:PRIMARY> use test
switched to db test
mymon:PRIMARY> db.test.insert({name:"liyao", age:25})
WriteResult({ "nInserted" : 1 })
mymon:PRIMARY>node2004:
> rs.initiate(config)
....
mymon:SECONDARY> use test
switched to db test
mymon:SECONDARY> db.test.find()
Error: error: {
"operationTime" : Timestamp(1545903758, 1),
"ok" : 0,
"errmsg" : "not master and slaveOk=false", //不是master是不允许读写的
"code" : 13435,
"codeName" : "NotMasterNoSlaveOk",
"$clusterTime" : {
"clusterTime" : Timestamp(1545903758, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
mymon:SECONDARY> db.setSlaveOk() //允许读写
mymon:SECONDARY> db.test.find() //查看数据
{ "_id" : ObjectId("5c249e73345ffcc8fc7205cc"), "name" : "liyao", "age" : 25 }
mymon:SECONDARY> 验证成功，数据复制OK
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