A, Replica Set cluster is divided into two architectures:
- An odd number of nodes constituting Replica Set, all the data sets owned by the node. Minimum architecture: a Primary node, two Secondary nodes
- Replica Set + even number of nodes consisting of an arbitration node, the node that owns the data set, only nodes involved in arbitration arbitration elected Primary node. Minimum architecture: a Primary node, a Secondary node, a node Arbiter
Take the next three servers, for example, deployment framework with arbitration.
| IP addresses | Operating system version | MongoDB version | port | Features |
| 10.10.18.10 | 7.5 | 4.0 | 27017 | Primary |
| 10.10.18.11 | Centos7.5 | 4.0 | 27017 | Secondary |
| 10.10.18.12 | Centos7.5 | 4.0 | 27017 | Arbiter |
Two, MongoDB installation and deployment
Installation Environment: CentOS 7.5
Mounting base dependencies
yum install cyrus-sasl cyrus-sasl-gssapi cyrus-sasl-plain krb5-libs libcurl libpcap lm_sensors-libs net-snmp net-snmp-agent-libs openldap openssl rpm-libs tcp_wrappers-libs
Download the installation package
https://fastdl.mongodb.org/linux/mongodb-linux-x86_64-4.0.10.tgz
Resolve installation package
tar -xzvf mongodb-linux-x86_64-4.0.10.tgz -C /data/
ln -s /data/mongodb-linux-x86_64-4.0.10 /data/mongodb
Adding Environment Variables
echo "export PATH=\$PATH:/data/mongodb/bin" >> ~/.bashrc
source ~/.bashrc
mongo --version
Primary configuration file:
systemLog:
destination: file
path: "/data/mongodb/log/mongod.log"
logAppend: true
storage:
dbPath: "/data/mongodb/data"
journal:
enabled: true
wiredTiger:
engineConfig:
cacheSizeGB: 2
processManagement:
fork: true
pidFilePath: "/data/mongodb/pid/m.pid"
net:
bindIp: 10.10.18.10
port: 27017
replication:
replSetName: "rs0"
Secondary profile
systemLog:
destination: file
path: "/data/mongodb/log/mongod.log"
logAppend: true
storage:
dbPath: "/data/mongodb/data"
journal:
enabled: true
wiredTiger:
engineConfig:
cacheSizeGB: 2
processManagement:
fork: true
pidFilePath: "/data/mongodb/pid/m.pid"
net:
bindIp: 10.10.18.11
port: 27017
replication:
replSetName: "rs0"
Arbiter's profile
systemLog:
destination: file
path: "/data/mongodb/log/mongod.log"
logAppend: true
storage:
dbPath: "/data/mongodb/data"
journal:
enabled: true
wiredTiger:
engineConfig:
cacheSizeGB: 2
processManagement:
fork: true
pidFilePath: "/data/mongodb/pid/m.pid"
net:
bindIp: 10.10.18.12
port: 27017
replication:
replSetName: "rs0"
Start mongdb on all three servers
mongod -f /data/mongodb/mongod.conf
Third, configure the Replica Set
Log in Renyiyitai three servers, log mongo
mongo --host 10.10.18.10
>cfg={ _id:"rs0",members:[{_id:0,host:'10.10.18.10:27017',priority:1},{_id:1,host:'10.10.18.11:27017',priority:1},{_id:2,host:'10.10.18.12:27017',arbiterOnly:true}] };
>rs.initiate(cfg)
View Replica Set Configuration
> rs.conf()
{
"_id" : "rs0",
"version" : 1,
"protocolVersion" : NumberLong(1),
"writeConcernMajorityJournalDefault" : true,
"members" : [
{
"_id" : 0,
"host" : "10.10.18.10:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 1,
"host" : "10.10.18.11:27017",
"arbiterOnly" : false,
"buildIndexes" : true,
"hidden" : false,
"priority" : 1,
"tags" : {
},
"slaveDelay" : NumberLong(0),
"votes" : 1
},
{
"_id" : 2,
"host" : "10.10.18.12:27017",
"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("5cff76e5e57e23a5bc7054e2")
}
}
Fourth, verification Replica Set
Primary data is inserted in the
rs0:PRIMARY> show dbs
admin 0.000GB
config 0.000GB
local 0.000GB
rs0:PRIMARY> db.users.insertOne(
... {
... name:"sue",
... age: 26,
... status:"pending"
... })
{
"acknowledged" : true,
"insertedId" : ObjectId("5cff79e8993e70290a081d04")
}
rs0:PRIMARY> db.users.find()
{ "_id" : ObjectId("5cff79e8993e70290a081d04"), "name" : "sue", "age" : 26, "status" : "pending" }
In Secondary, the default is not allowed to read
rs0:SECONDARY> db.users.find()
Error: error: {
"operationTime" : Timestamp(1560247181, 1),
"ok" : 0,
"errmsg" : "not master and slaveOk=false",
"code" : 13435,
"codeName" : "NotMasterNoSlaveOk",
"$clusterTime" : {
"clusterTime" : Timestamp(1560247181, 1),
"signature" : {
"hash" : BinData(0,"AAAAAAAAAAAAAAAAAAAAAAAAAAA="),
"keyId" : NumberLong(0)
}
}
}
Five, fault simulation
Stop mongo process on the Primary, Secondary login mongo viewed on
mongo --host 10.10.18.11
rs0:PRIMARY> db.users.find()
{ "_id" : ObjectId("5cff79e8993e70290a081d04"), "name" : "sue", "age" : 26, "status" : "pending" }
I found the original Secondary becomes Primary, and can be queried.
Mongo open process on the original Primary server, which becomes Secondary.