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MongoDB Cluster Setup Centos

tomahawkpilot profile image syamkumar ・Updated on ・5 min read

We will be setting up Mongo DB for high availability using 3 virtual machines

1) Mongo Primary (t3a.medium)
2) Mongo Secondary (t3a.medium)
3) Mongo Arbiter (t3a.small)

Let's begin the system preparations

The following setup has to be done in all 3 machines

  • login as sudo in each machine
sudo --login 
  • Update centos packages to the latest version Centos 7
yum update -y

Centos 8

dnf update -y
  • install Nano editor (I am a Nano fan) Centos 7
yum install nano -y

Centos 8

dnf install nano -y
  • add hosts values edit the nano /etc/hosts file to add the following entries
172.31.28.16 mongo1
172.31.31.194 mongo2
172.31.25.65 mongo3

important Step

Disable SELinux as it has breaking effects on internode connection
edit /etc/selinux/config
change

SELINUX=disabled

do the above step in all 3 machines and make sure to do a reboot by running

reboot

Now Install Mongo

  • Configure the package management system

Create a nano /etc/yum.repos.d/mongodb-org-4.4.repo file so that you can install MongoDB directly using yum

Add the following content to it.

[mongodb-org-4.4]
name=MongoDB Repository
baseurl=https://repo.mongodb.org/yum/redhat/$releasever/mongodb-org/4.4/x86_64/
gpgcheck=1
enabled=1
gpgkey=https://www.mongodb.org/static/pgp/server-4.4.asc
  • Install Mongo DB latest Stable Centos 7
yum install -y mongodb-org

Centos 8

dnf install -y mongodb-org

Before we can begin cluster Setup lets prepare mongo

Enable Mongo Authentication

To add authentication to mongo add the following lines to
nano /etc/mongod.conf

security:
    authorization: enabled

Then do a restart

service mongod restart
  • let's create mongodb user Open mongo shell

mongo

the following commands

use admin
db.createUser({
    user: "tomahawk",
    pwd: "tomahawkPilot",
    roles: [ 
        { 
            role: "userAdminAnyDatabase", 
            db: "admin" 
        },
        {
            role: "clusterAdmin",
             db: "admin"
        },
        {
            role: "root,
            db: "admin
        }
    ]
})

Now let's Begin the Replication Configuration

  • Add replSet to mongod.conf in all 3 machines edit your nano /etc/mongod.conf file
replication:
  replSetName: rs0

Keyfile Access Control on Replica Set

navigate to your mongo path

/var/lib/mongo in my case

Use the following command to generate a keyfile

openssl rand -base64 756 > keyfile

Copy the key file to all 3 machines
add Appropriate permissions

chmod 400 keyfile
chown mongod:mongod keyfile

Now add the keyfile to your nano /etc/mongod.conf file

security:
    authorization: enabled
    keyFile: /var/lib/mongo/keyfile
  • do a restart of all mongod services
systemctl restart mongod

for the changes in replication to take effect before initializing the replica

  • On mongo1
use admin
db.auth("tomahawk","tomahawkPilot");
rs.initiate(
   {
      _id: "rs0",
      version: 1,
      members: [
         { _id: 0, host : "mongo1:27017" }
      ]
   }
)

You can always run

mongo --port 27017 -u tomahawk --authenticationDatabase 'admin' -p tomahawkPilot

to directly login to the cluster

Now let's create the replica set

rs.add("mongo2:27017");

Check connection status by running

rs.status()

On Successful connection, you will get a response

rs.status()
{
        "set" : "rs0",
        "date" : ISODate("2020-08-10T14:03:42.405Z"),
        "myState" : 1,
        "term" : NumberLong(2),
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 2,
        "writeMajorityCount" : 2,
        "votingMembersCount" : 2,
        "writableVotingMembersCount" : 2,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1597068221, 2),
                        "t" : NumberLong(2)
                },
                "lastCommittedWallTime" : ISODate("2020-08-10T14:03:41.727Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1597068221, 2),
                        "t" : NumberLong(2)
                },
                "readConcernMajorityWallTime" : ISODate("2020-08-10T14:03:41.727Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1597068221, 2),
                        "t" : NumberLong(2)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1597068221, 2),
                        "t" : NumberLong(2)
                },
                "lastAppliedWallTime" : ISODate("2020-08-10T14:03:41.727Z"),
                "lastDurableWallTime" : ISODate("2020-08-10T14:03:41.727Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1597066170, 1),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2020-08-10T14:03:41.721Z"),
                "electionTerm" : NumberLong(2),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1597066987, 1),
                        "t" : NumberLong(1)
                },
                "numVotesNeeded" : 2,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "numCatchUpOps" : NumberLong(0),
                "newTermStartDate" : ISODate("2020-08-10T14:03:41.727Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2020-08-10T14:03:41.898Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "mongo1:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 454,
                        "optime" : {
                                "ts" : Timestamp(1597068221, 2),
                                "t" : NumberLong(2)
                        },
                        "optimeDate" : ISODate("2020-08-10T14:03:41Z"),
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "electionTime" : Timestamp(1597068221, 1),
                        "electionDate" : ISODate("2020-08-10T14:03:41Z"),
                        "configVersion" : 2,
                        "configTerm" : 2,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "mongo2:27017",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 7,
                        "optime" : {
                                "ts" : Timestamp(1597066987, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1597066987, 1),
                                "t" : NumberLong(1)
                        },
                        "optimeDate" : ISODate("2020-08-10T13:43:07Z"),
                        "optimeDurableDate" : ISODate("2020-08-10T13:43:07Z"),
                        "lastHeartbeat" : ISODate("2020-08-10T14:03:41.727Z"),
                        "lastHeartbeatRecv" : ISODate("2020-08-10T14:03:42.261Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 2,
                        "configTerm" : 1
                }
        ],
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1597068221, 2),
                "signature" : {
                        "hash" : BinData(0,"17CdXYPWQ6I24TCLhxpQt8nGGPk="),
                        "keyId" : NumberLong("6859346398467325956")
                }
        },
        "operationTime" : Timestamp(1597068221, 2)
}
rs0:PRIMARY> 

Setting up the Arbiter

rs.addArb("mongo3:27017");
{
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1597068567, 1),
                "signature" : {
                        "hash" : BinData(0,"q5F6v883q8+1gBfmEJtwINbXAYY="),
                        "keyId" : NumberLong("6859346398467325956")
                }
        },
        "operationTime" : Timestamp(1597068567, 1)
}

Now check connection status by running

rs.status()

rs.status()

rs0:PRIMARY> rs.status()
{
        "set" : "rs0",
        "date" : ISODate("2020-08-10T14:10:18.328Z"),
        "myState" : 1,
        "term" : NumberLong(2),
        "syncSourceHost" : "",
        "syncSourceId" : -1,
        "heartbeatIntervalMillis" : NumberLong(2000),
        "majorityVoteCount" : 2,
        "writeMajorityCount" : 2,
        "votingMembersCount" : 3,
        "writableVotingMembersCount" : 2,
        "optimes" : {
                "lastCommittedOpTime" : {
                        "ts" : Timestamp(1597068611, 1),
                        "t" : NumberLong(2)
                },
                "lastCommittedWallTime" : ISODate("2020-08-10T14:10:11.737Z"),
                "readConcernMajorityOpTime" : {
                        "ts" : Timestamp(1597068611, 1),
                        "t" : NumberLong(2)
                },
                "readConcernMajorityWallTime" : ISODate("2020-08-10T14:10:11.737Z"),
                "appliedOpTime" : {
                        "ts" : Timestamp(1597068611, 1),
                        "t" : NumberLong(2)
                },
                "durableOpTime" : {
                        "ts" : Timestamp(1597068611, 1),
                        "t" : NumberLong(2)
                },
                "lastAppliedWallTime" : ISODate("2020-08-10T14:10:11.737Z"),
                "lastDurableWallTime" : ISODate("2020-08-10T14:10:11.737Z")
        },
        "lastStableRecoveryTimestamp" : Timestamp(1597068601, 1),
        "electionCandidateMetrics" : {
                "lastElectionReason" : "electionTimeout",
                "lastElectionDate" : ISODate("2020-08-10T14:03:41.721Z"),
                "electionTerm" : NumberLong(2),
                "lastCommittedOpTimeAtElection" : {
                        "ts" : Timestamp(0, 0),
                        "t" : NumberLong(-1)
                },
                "lastSeenOpTimeAtElection" : {
                        "ts" : Timestamp(1597066987, 1),
                        "t" : NumberLong(1)
                },
                "numVotesNeeded" : 2,
                "priorityAtElection" : 1,
                "electionTimeoutMillis" : NumberLong(10000),
                "numCatchUpOps" : NumberLong(0),
                "newTermStartDate" : ISODate("2020-08-10T14:03:41.727Z"),
                "wMajorityWriteAvailabilityDate" : ISODate("2020-08-10T14:03:41.898Z")
        },
        "members" : [
                {
                        "_id" : 0,
                        "name" : "mongo1:27017",
                        "health" : 1,
                        "state" : 1,
                        "stateStr" : "PRIMARY",
                        "uptime" : 850,
                        "optime" : {
                                "ts" : Timestamp(1597068611, 1),
                                "t" : NumberLong(2)
                        },
                        "optimeDate" : ISODate("2020-08-10T14:10:11Z"),
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "electionTime" : Timestamp(1597068221, 1),
                        "electionDate" : ISODate("2020-08-10T14:03:41Z"),
                        "configVersion" : 3,
                        "configTerm" : 2,
                        "self" : true,
                        "lastHeartbeatMessage" : ""
                },
                {
                        "_id" : 1,
                        "name" : "mongo2:27017",
                        "health" : 1,
                        "state" : 2,
                        "stateStr" : "SECONDARY",
                        "uptime" : 403,
                        "optime" : {
                                "ts" : Timestamp(1597068611, 1),
                                "t" : NumberLong(2)
                        },
                        "optimeDurable" : {
                                "ts" : Timestamp(1597068611, 1),
                                "t" : NumberLong(2)
                        },
                        "optimeDate" : ISODate("2020-08-10T14:10:11Z"),
                        "optimeDurableDate" : ISODate("2020-08-10T14:10:11Z"),
                        "lastHeartbeat" : ISODate("2020-08-10T14:10:17.346Z"),
                        "lastHeartbeatRecv" : ISODate("2020-08-10T14:10:17.389Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncSourceHost" : "mongo1:27017",
                        "syncSourceId" : 0,
                        "infoMessage" : "",
                        "configVersion" : 3,
                        "configTerm" : 2
                },
                {
                        "_id" : 2,
                        "name" : "mongo3:27017",
                        "health" : 1,
                        "state" : 7,
                        "stateStr" : "ARBITER",
                        "uptime" : 50,
                        "lastHeartbeat" : ISODate("2020-08-10T14:10:17.351Z"),
                        "lastHeartbeatRecv" : ISODate("2020-08-10T14:10:17.471Z"),
                        "pingMs" : NumberLong(0),
                        "lastHeartbeatMessage" : "",
                        "syncSourceHost" : "",
                        "syncSourceId" : -1,
                        "infoMessage" : "",
                        "configVersion" : 3,
                        "configTerm" : 2
                }
        ],
        "ok" : 1,
        "$clusterTime" : {
                "clusterTime" : Timestamp(1597068611, 1),
                "signature" : {
                        "hash" : BinData(0,"Pir6qAUNxIu6/AbFv6fCxpVVwOs="),
                        "keyId" : NumberLong("6859346398467325956")
                }
        },
        "operationTime" : Timestamp(1597068611, 1)
}

now run

rs.conf()

to see your config

rs0:PRIMARY> rs.conf()
{
        "_id" : "rs0",
        "version" : 3,
        "term" : 2,
        "protocolVersion" : NumberLong(1),
        "writeConcernMajorityJournalDefault" : true,
        "members" : [
                {
                        "_id" : 0,
                        "host" : "mongo1:27017",
                        "arbiterOnly" : false,
                        "buildIndexes" : true,
                        "hidden" : false,
                        "priority" : 1,
                        "tags" : {

                        },
                        "slaveDelay" : NumberLong(0),
                        "votes" : 1
                },
                {
                        "_id" : 1,
                        "host" : "mongo2:27017",
                        "arbiterOnly" : false,
                        "buildIndexes" : true,
                        "hidden" : false,
                        "priority" : 1,
                        "tags" : {

                        },
                        "slaveDelay" : NumberLong(0),
                        "votes" : 1
                },
                {
                        "_id" : 2,
                        "host" : "mongo3:27017",
                        "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("5f314b35458f8460ab22cda1")
        }
}

Have an awesome day ahead

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