How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04 (Tutorial)
How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04. Database clustering is a concept that involves multiple servers which are connected to a single primary database. Clustering is a key aspect in production environments to ensure data redundancy, fault tolerance, high availability and load balancing. In this guide, we will demonstrate how to create a MongoDB multi node cluster on Ubuntu 22.04.
Please read on How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04.
What is a MongoDB Multi-Node Cluster?
One of the benefits of MongoDB is that it supports real-time replication of data across multiple servers or nodes. In contrast to a single server MongoDB database, a multi-node cluster comprises a primary server that accepts read and write operations , and two or more secondary servers on which data will be copied or replicated. Replication is made possible across the cluster using a replica set.
A MongoDB replica set is a group of MongoDB instances that maintain consistency of the same data set across a cluster. It enforces replication across by providing redundancy and high availability in the cluster. Without a replica set in a MongoDB deployment, data would only be saved in the primary node. This would mean that in case of any failure in the primary node, all the data would be lost.
Advantages of implementing a Multi-Node cluster
As previously discussed, a multi node cluster provides the following benefits.
Data Redundancy
In a multi node cluster, all servers are synchronized to store the exact same data. This implies that the primary server has exactly the same data set as the secondary node and this ensures data redundancy which comes in handy in case of a failure on one of the nodes.
Scalability
Scalability is not achieved by default in a database. It is only achieved through database clustering where data is evenly spread out across multiple servers. A multi-node cluster offers horizontal scaling, which in turn, ensures high availability of data.
High Availability
High availability refers to maintenance of high levels of uptime, often well above the SLAs. This is achieved by eliminating single points of failure, which is made possible through horizontal scaling. High availability ensures that you can access your data at any given time.
Compliance
Implementing a multi-node cluster in a production environment ensures compliance with the relevant laws.
How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04
Lab Setup
For demonstration , we have a 3-node cluster environment as shown . We have a primary node and two secondary nodes.
- 173.82.240.178 mongo-master-node
- 173.82.240.203 mongo-node-1
- 173.82.240.100 mongo-node-2
Without much further ado, let us get started with setting up a MongoDB multi node cluster.
Step 1: Update the hosts file
To get started, you need to update the hosts file of each node with the IP address and hostname of each node. So, access the file:
$ sudo nano /etc/hosts
Append the following lines to the file. Be sure to update the IP address and the hostname to correspond with your own setup.
173.82.240.178 mongo-master-node
173.82.240.203 mongo-node-1
173.82.240.100 mongo-node-2
Save the changes and exit the file.
Step 2: Install MongoDB
The next step is to install MongoDB on all the nodes in your cluster setup. So, log into each node and start by refreshing the local package index.
$ sudo apt update
Once the system is up to date, install the following essential packages.
$ sudo apt install software-properties-common gnupg apt-transport-https ca-certificates -y
Moving on, we will install MongoDB 5.0 which is the latest release at the time of writing this guide. Therefore, begin by adding the MongoDB GPG key.
$ wget -qO - https://www.mongodb.org/static/pgp/server-5.0.asc | sudo apt-key add -
Command Output looks like this
OK
Next, add the MongoDB 5.0 repository to the/etc/apt/sources.list.d directory
$ echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/5.0 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-5.0.list
Then the Command Output should be like this
deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu focal/mongodb-org/5.0 multiverse
With the repository in place please update the package lists to notify the system about the newly added repository.
$ sudo apt update
Then install MongoDB database server.
$ sudo apt install mongodb-org -y
When the installation is complete, verify that MongoDB server is installed as shown.
$ mongod --version
You will get this Command Output
db version v5.0.9
Build Info: {
"version": "5.0.9",
"gitVersion": "6f7dae919422dcd7f4892c10ff20cdc721ad00e6",
"openSSLVersion": "OpenSSL 1.1.1f 31 Mar 2020",
"modules": [],
"allocator": "tcmalloc",
"environment": {
"distmod": "ubuntu2004",
"distarch": "x86_64",
"target_arch": "x86_64"
}
}
Next step is to start and enable MongoDB daemon using the following commands:
$ sudo systemctl start mongod
$ sudo systemctl enable mongod
Then verify that MongoDB service is running.
$ sudo systemctl status mongod
Your Command Output
● mongod.service - MongoDB Database Server
Loaded: loaded (/lib/systemd/system/mongod.service; disabled; vendor preset: enabled)
Active: active (running) since Fri 2022-06-17 12:28:15 UTC; 6min ago
Docs: https://docs.mongodb.org/manual
Main PID: 14582 (mongod)
Memory: 63.0M
CGroup: /system.slice/mongod.service
└─14582 /usr/bin/mongod --config /etc/mongod.conf
Jul 17 10:20:15 ubuntu systemd[1]: Started MongoDB Database Server.
Step 3: Create Administrative User on Master Node
Following step is to create an administrative user on the master node. The administrative user will be used to create a replica set which will be replicated across the two client nodes.
So, access the MongoDB shell.
$ mongosh
Switch the database to admin user:
use admin
Now in here please create an admin user as follows. The ‘passwordPrompt()‘ will prompt you to enter the admin password.
db.createUser(
{
user: "admin-user",
pwd: passwordPrompt(),
roles: [ { role: "root", db: "admin" }, "readWriteAnyDatabase" ]
}
)
Once you have created the Administrative user, exit the shell.
exit
Step 4: Configure the Master Node
Moving on, you will be required to generate a key file that will be used to secure authentication across the nodes in the cluster. To generate the key, we will use the openssl command.
So, first, switch to root user.
$ sudo su
Following step is to generate the key file as follows.
# openssl rand -base64 756 > /mnt/keyfile
Next assign the necessary file ownership and permissions.
# chmod 400 /mnt/keyfile
# chown mongodb:mongodb /mnt/keyfile
Copy the key file to all the nodes in your cluster.
# scp /mnt/keyfile root@173.82.240.203:/mnt/
# scp /mnt/keyfile root@173.82.240.100:/mnt/
Here please access the default MongoDB configuration file.
# sudo vim /etc/mongod.conf
Update the configuration file as shown. The Replica Set Name is an arbitrary value and you can give it your preferred name.
net:
port: 27017
bindIp: 127.0.0.1,mongo-master-node
security:
keyFile: /mnt/keyfile
replication:
replSetName: "replica01"
Save the changes and exit the configuration file.
Step 5: Configure the client nodes
In this step log into each of the client nodes and edit the main configuration file.
$ sudo vim /etc/mongod.conf
For Node 1
net:
port: 27017
bindIp: 127.0.0.1,mongo-node-1
security:
keyFile: /mnt/keyfile
replication:
replSetName: "replica01"
Save the changes and exit the configuration file.
Next apply the following ownership and permissions to the key file that was copied.
# chmod 400 /mnt/keyfile
# chown mongodb:mongodb /mnt/keyfile
For the changes to take effect, restart MongoDB service.
$ sudo systemctl restart mongod
Repeat the same for the remaining client node.
For Node 2
Login and access the main configuration file.
$ sudo vim /etc/mongod.conf
Make the following changes.
net:
port: 27017
bindIp: 127.0.0.1,mongo-node-2
security:
keyFile: /mnt/keyfile
replication:
replSetName: "replica01"
Save the changes and exit.
As before, assign the following ownership and file permissions.
# chmod 400 /mnt/keyfile
# chown mongodb:mongodb /mnt/keyfile
Be sure to restart MongoDB service to apply the changes made.
$ sudo systemctl restart mongod
Step 6: Initiate the Replica Set
In this section, we will create a replica set on the master node and later verify replication of the data defined in the replica set.
On the master node, authenticate as the administrative user.
# mongosh -u admin -p --authenticationDatabase admin
Initialize the replica set as follows.
rs.initiate()
And your Command Output should be like this
{
info2: 'no configuration specified. Using a default configuration for the set',
me: '173.82.240.178:27017',
ok: 1
}
Next step is to add the first node to the cluster.
rs.add("mongo-node-1")
Similarly, add the second client node.
rs.add("mongo-node-2")
Command Output
At this point, all the nodes have been added to the cluster. To check the status of the replica set, run the command:
rs.status()
Command Output
replica01 [direct: primary] test > rs.status()
{
set: 'replica01',
date: ISODate("2022-07-13T20:22:53.088Z"),
myState: 1,
term: Long("1"),
syncSourceHost: '',
syncSourceId: -1,
heartbeatIntervalMillis: Long("2000"),
majorityVoteCount: 2,
writeMajorityCount: 2,
votingMembersCount: 3,
writableVotingMembersCount: 3,
optimes: {
lastCommittedOpTime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
lastCommittedWallTime: ISODate("2022-07-13T20:22:47.186Z"),
readConcernMajorityOpTime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
appliedOpTime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
durableOpTime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
lastAppliedWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastDurableWallTime: ISODate("2022-07-13T20:22:47.186Z")
},
lastStableRecoveryTimestamp: Timestamp({ t: 1657743717, i: 1 }),
electionCandidateMetrics: {
lastElectionReason: 'electionTimeout',
lastElectionDate: ISODate("2022-07-13T20:17:06.963Z"),
electionTerm: Long("1"),
lastCommittedOpTimeAtElection: { ts: Timestamp({ t: 1657743426, i: 1 }), t: Long("-1") },
lastSeenOpTimeAtElection: { ts: Timestamp({ t: 1657743426, i: 1 }), t: Long("-1") },
numVotesNeeded: 1,
priorityAtElection: 1,
electionTimeoutMillis: Long("10000"),
newTermStartDate: ISODate("2022-07-13T20:17:07.061Z"),
wMajorityWriteAvailabilityDate: ISODate("2022-07-13T20:17:07.152Z")
},
members: [
{
_id: 0,
name: '173.82.240.178:27017',
health: 1,
state: 1,
stateStr: 'PRIMARY',
uptime: 539,
optime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
optimeDate: ISODate("2022-07-13T20:22:47.000Z"),
lastAppliedWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastDurableWallTime: ISODate("2022-07-13T20:22:47.186Z"),
syncSourceHost: '',
syncSourceId: -1,
infoMessage: '',
electionTime: Timestamp({ t: 1657743426, i: 2 }),
electionDate: ISODate("2022-07-13T20:17:06.000Z"),
configVersion: 5,
configTerm: 1,
self: true,
lastHeartbeatMessage: ''
},
{
_id: 1,
name: 'mongo-node-1:27017',
health: 1,
state: 2,
stateStr: 'SECONDARY',
uptime: 222,
optime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
optimeDurable: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
optimeDate: ISODate("2022-07-13T20:22:47.000Z"),
optimeDurableDate: ISODate("2022-07-13T20:22:47.000Z"),
lastAppliedWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastDurableWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastHeartbeat: ISODate("2022-07-13T20:22:52.451Z"),
lastHeartbeatRecv: ISODate("2022-07-13T20:22:52.464Z"),
pingMs: Long("0"),
lastHeartbeatMessage: '',
syncSourceHost: '173.82.240.178:27017',
syncSourceId: 0,
infoMessage: '',
configVersion: 5,
configTerm: 1
},
{
_id: 2,
name: 'mongo-node-2:27017',
health: 1,
state: 2,
stateStr: 'SECONDARY',
uptime: 174,
optime: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
optimeDurable: { ts: Timestamp({ t: 1657743767, i: 1 }), t: Long("1") },
optimeDate: ISODate("2022-07-13T20:22:47.000Z"),
optimeDurableDate: ISODate("2022-07-13T20:22:47.000Z"),
lastAppliedWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastDurableWallTime: ISODate("2022-07-13T20:22:47.186Z"),
lastHeartbeat: ISODate("2022-07-13T20:22:52.500Z"),
lastHeartbeatRecv: ISODate("2022-07-13T20:22:51.486Z"),
pingMs: Long("0"),
lastHeartbeatMessage: '',
syncSourceHost: 'mongo-node-1:27017',
syncSourceId: 1,
infoMessage: '',
configVersion: 5,
configTerm: 1
}
],
ok: 1,
'$clusterTime': {
clusterTime: Timestamp({ t: 1657743767, i: 1 }),
signature: {
hash: Binary(Buffer.from("84b17e5c768b301786b693ea6d4292b200ab01c7", "hex"), 0),
keyId: Long("7119953804123963394")
}
},
operationTime: Timestamp({ t: 1657743767, i: 1 })
}
Step 7: Verify replication on client nodes
To simulate simulation of the replica set across the client nodes, we are going to create a database on the master node and add some values to it.
On the master node, authenticate as the Administrative user.
# mongosh -u admin-user -p --authenticationDatabase admin
Please create a database. In this case, we will create a sample database called testdb.
use testdb
Here create a collection and add a record. In this example, we are creating a collection called ‘employees‘ that contains employee details.
db.employees.insert({Name: "Andrew", Age: 25, City: "London", Status: "Married"})
Command Output
To verify the newly created record, run the command:
db.employees.find()
Command Output
[
{
_id: ObjectId("62cf2cbde6e12dec1af9354b"),
Name: 'Andrew',
Age: 25,
City: 'London',
Status: 'Married'
}
]
You can also verify the existence of the database.
show dbs
Command Output
Now, head over to any of the client nodes and login to MongoDB as the Administrative user.
mongosh -u admin-user -p --authenticationDatabase admin
Once logged in enable the secondary member read operations on a per-connection basis using the following command
db.getMongo().setReadPref("primaryPreferred")
Finally, switch to the test database and list the documents in the collection.
use testdb
db.employees.find()
Command Output
This is sure confirmation that the replication is working as expected !
So thank you for reading How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04. It’s time to summarize.
How to Create MongoDB Cluster Multi-Node on Ubuntu 20.04 Conclusion
This wraps up our guide. In this tutorial, we have demonstrated how to setup and configure a multi-node MongoDB cluster and how to create a replica set and verify replication on secondary nodes. A multi-node cluster environment ensures that copies of your data are available on different servers, and this ensures data redundancy, and high availability. For more information about MongoDB clusters and replication, check out the Official MongoDB documentation.
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