MongoDB Cluster with 3 Linux Instances

Follow the below steps to set up a 3-node MongoDB cluster:

Update && Upgrade all nodes

$ sudo apt-get update -y && ap-get upgrade -y

Configuring DNS Resolution

On Linux and other Unix-like systems, the hosts file is located in the /etc/ directory. To edit this file on each of your three servers, use your preferred text editor.

$ vi /etc/hosts

Server Hostname Configuration

Configuring your servers with descriptive hostnames is advisable as it enhances clarity and ease of management.

• mongo0.replset.member

• mongo1.replset.member

• mongo2.replset.member

Using these hostnames, your /etc/hosts files would look similar to the following highlighted lines:

Import the MongoDB GPG Key

First, you need to import the MongoDB GPG key to ensure the authenticity of the software packages:

To obtain the most recent version of this software, you must include MongoDB’s dedicated package repository in your APT sources. Then, you’ll be able to install, a meta-package that always points to the latest version of MongoDB.

To start, import the public GPG key for the latest stable version of MongoDB by running the following command

$ wget -qO - https://www.mongodb.org/static/pgp/server-4.4.asc | sudo apt-key add -

Add MongoDB Repository

Next, you'll add the MongoDB repository to your system's repository list:

APT (Advanced Package Tool) relies on two key locations to find online package repositories for downloading and installing software: the sources.list file and the sources.list.d directory. The sources.list file contains a list of repository sources, each on a separate line, with the most preferred sources at the beginning of the list. Meanwhile, the sources.list.d directory offers a way to manage additional repository sources by placing them in separate files, making repository management more modular and organized.

Run the following command, which creates a file in the sources.list.d directory named mongodb-org-4.4.list.

$ echo "deb [ arch=amd64,arm64 ] https://repo.mongodb.org/apt/ubuntu $(lsb_release -sc)/mongodb-org/4.4 multiverse" | sudo tee /etc/apt/sources.list.d/mongodb-org-4.4.list

After running this command, update your server’s local package index so APT knows where to find the mongodb-org package:

$ sudo apt-get update -y

Install MongoDB

Now, you can install MongoDB using the following command:

$ sudo apt-get install mongodb-org -y

This command will install the MongoDB package and its dependencies.

Start MongoDB Service

After installation, MongoDB should start automatically. You can verify the status of the service by running:

$ sudo systemctl status mongod

$ sudo systemctl start mongod

Enable MongoDB to Start on the Boot

$ sudo systemctl enable mongod

Verify Installation

To confirm MongoDB's successful installation, open the MongoDB shell by following these steps:

$ mongo --version

$ mongo

Enable Replication in Each Server's MongoDB Configuration File:-

By updating the /etc/hosts files on your servers, you've successfully set up hostnames to correlate with their respective IP addresses.

To modify the MongoDB database settings, edit the main configuration file located at /etc/mongod.conf. This file is automatically generated during the MongoDB installation process.

Use a text editor vito open and modify the file. Here’s the command:

$ vi /etc/mongod.conf

In MongoDB, various configuration options allow you to customize the server's behavior. The systemLog option controls the logging settings of your database, enabling you to define what gets logged and where. On the other hand, the net option is pivotal for adjusting network-related settings, offering control over aspects like port configuration and network interfaces.

here change the in each server IP 127.0.0.0 > 0.0.0.0

Create a mongo key file in each server

$ mkdir -p /etc/mongodb/key-files/

Now create an OpenSSL and run these commands

$ openssl rand -base64 756 > /etc/mongodb/key-files/mongo-key

Copy these mongo-key files in another 2 vms

$ sftp root@your_IP_address

Enabling Replication in Each Server's MongoDB Configuration File

After copying the necessary files, proceed by adding the specified keys to the /etc/mongod.conf file on each server.

$ vi /etc/mongod.conf

Uncomment the security option and add the key

Add the key

keyFile: /etc/mongodb/key-files/mongo-key

Configure the file permissions and ownership in each server

$ chmod 400 /etc/mongodb/key-files/mongo-key

$ chown -R mongodb:mongodb /etc/mongodb

Before executing the following command, ensure the Mongod service is stopped.

$ systemctl stop mongod

Replication runs these commands in all nodes for set replset

$ /usr/bin/mongod --replSet "evermight" --config /etc/mongod.conf --fork

Also add replication all nodes

$ systemctl start mongod

Starting the Replica Set and Adding Members:

After setting up your three MongoDB instances, initiate replication by opening a MongoDB shell and adding each instance as a replication member.

$ mongo

To begin the replication process, execute these commands:

mongo> rs.initiate({_id: "evermight", members: [{_id: 1, host: "mongo1"},{_id: 2, host: "mongo2"}] });

Conclusion

MongoDB is a free, open-source NoSQL database management system (DBMS) popular for large-scale websites or applications. Since it doesn’t use a fixed schematic structure to store data, it is more flexible and scalable than SQL..