AWS, Cloud Computing

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Migrating MongoDB to a Multi-Node Replica Set on Amazon EC2

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Overview

High availability and fault tolerance are crucial for any production-grade database system. MongoDB offers built-in support for replication via Replica Sets, which maintains multiple copies of your data across different instances. In this guide, we walk through migrating MongoDB to a multi-node replica set using Amazon EC2 instances, including the setup of primary, secondary, and arbiter nodes. We will also briefly integrate supporting AWS services like AWS IAM, Amazon S3 for backup, and Amazon CloudWatch for monitoring.

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Introduction

Replica sets in MongoDB provide redundancy and high availability. A replica set consists of a primary node receiving all write operations and one or more secondary nodes replicating the primary data. An optional arbiter node can be added to participate in elections without storing data.

This blog details a step-by-step approach to migrate and deploy MongoDB on three Amazon EC2 instances, configure replication, and automate monitoring using AWS-native tools for enhanced observability and security.

Prerequisites

Before you begin, ensure the following:

  • You have three Ubuntu 20.04+ EC2 instances (Primary, Secondary, and Arbiter) in the same Amazon VPC with appropriate Security Group rules (allowing internal communication on port 27017).
  • Amazon EC2 instances are launched with AWS IAM roles for secure access to Amazon S3 (optional backup) or Amazon CloudWatch.
  • SSH access is enabled via a private key, and you have root/sudo privileges.
  • Basic familiarity with Linux terminal, AWS Console, and MongoDB is helpful.

Step-by-Step Guide

  1. Install MongoDB on Secondary and Other Nodes

Create a user-data script for cloud-init or manual execution on the secondary and arbiter nodes:

  1. MongoDB Replica Set Configuration Script

Run the following script on all nodes, adjusting the IP addresses:

  1. Add Monitoring Script

On all nodes:

Advantages

  • High Availability: The replica set ensures the database remains available even if one node goes down.
  • Data Redundancy: Automatically replicates data across nodes to prevent data loss.
  • Automatic Failover: MongoDB automatically elects a new primary if the primary node fails.
  • Scalability: You can add more secondary nodes or convert to sharded clusters for horizontal scaling.
  • Read Distribution: Secondary nodes can serve read traffic if configured, improving performance.

Conclusion

Setting up a MongoDB replica set on Amazon EC2 ensures a production-ready architecture with high availability and resilience. This guide introduced essential setup concepts while abstracting sensitive commands to avoid misapplication.

You can further enhance this setup by:

  • Automating instance provisioning via AWS CloudFormation or Terraform.
  • Securing credentials using AWS IAM Roles and AWS Secrets Manager.
  • Enabling daily backups to Amazon S3 via a cron job or AWS Lambda.

Drop a query if you have any questions regarding Amazon EC2 and we will get back to you quickly.

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About CloudThat

CloudThat is an award-winning company and the first in India to offer cloud training and consulting services worldwide. As a Microsoft Solutions Partner, AWS Advanced Tier Training Partner, and Google Cloud Platform Partner, CloudThat has empowered over 850,000 professionals through 600+ cloud certifications winning global recognition for its training excellence including 20 MCT Trainers in Microsoft’s Global Top 100 and an impressive 12 awards in the last 8 years. CloudThat specializes in Cloud Migration, Data Platforms, DevOps, IoT, and cutting-edge technologies like Gen AI & AI/ML. It has delivered over 500 consulting projects for 250+ organizations in 30+ countries as it continues to empower professionals and enterprises to thrive in the digital-first world.

FAQs

1. What is the role of the arbiter in a replica set?

ANS: – Arbiters participate in elections but do not store data. They help break ties and maintain an odd number of votes for consistent elections.

2. Can I add more secondaries later?

ANS: – Yes, MongoDB supports dynamic reconfiguration of the replica set to add or remove members.

WRITTEN BY Dhruv Rajeshbhai Patel

Dhruv Patel is a Research Intern at CloudThat. He has completed his Master's in Computer Application and Cloud Certification in Azure and AWS. His area of interest lies in Cloud and Mobile Development Solutions. He loves to take ownership of the work that he is doing.

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