atlas-rs

Deploys a 5-node distributed Replica Set plus a regional read-only node in MongoDB Atlas (AWS).

Terraform Infrastructure

This repository now contains a Terraform project (in terraform/) that provisions:

• A MongoDB Atlas cluster in an existing Atlas Project
• A two-region (US-EAST-1 + US-EAST-2) advanced replica set cluster (5 electable nodes by default: 3 in US-EAST-1, 2 in US-EAST-2), plus an additional read-only node in AP-SOUTHEAST-2 (Sydney, Australia), running MongoDB 7.0. Note: Multi-region requires at least M30 instance size.

1. Setup

• Terraform >= 1.6
• MongoDB Atlas API Key with access to the target project
• Existing Atlas Project ID

The MongoDB Atlas provider requires credentials. Update the .env the following environment variables before terraform init/plan/apply:

cd terraform

source .env
terraform init
terraform validate
terraform plan
terraform apply

2. Run Demos

There are demo apps available to show the impact of read preference and write times to sharded clusters at:

• https://us.mdb-architect-day.net:3000 -https://au.mdb-architect-day.net:3000

One instance is deployed on an AWS EC2 node in US-EAST-1, the other in AP-SOUTHEAST-2.

2a. Localized Reads vs not so

The AU demo instance, in particualr, will show a significant drop in latency when switching from default 'PRIMARY' read preference, to 'NEAREST' read preference.

2b. Upgrade to MongoDB 8.0 while application is running.

See the step-by-step Terraform demo: demos/upgrade-mongodb-7-to-8/README.md:1

2c. Convert Replica Set to One-Shard Cluster

See the sharding upgrade demo: demos/replicaset-to-one-shard/README.md:1