AWS Route 53: Weighted Routing Policy

Introduction to Weighted Routing Policy

The Weighted Routing Policy in Amazon Route 53 allows you to distribute traffic across multiple resources by assigning them different weights. This approach provides fine-grained control over how DNS requests are directed to specific instances or endpoints.

How Weighted Routing Works

• You can assign a weight to each resource (e.g., EC2 instances).

• The weight determines the percentage of DNS requests that will be routed to that resource.

• Route 53 calculates the proportion of requests based on the formula:

  Traffic Percentage=Record Weight∑All Record Weights\text{Traffic Percentage} = \frac{\text{Record Weight}}{\sum \text{All Record Weights}}

• The weights do not need to sum up to 100; they are only relative to each other.

Example Scenario

Consider the following setup with three EC2 instances:

• 70% of traffic is routed to us-east-1.
• 20% of traffic is routed to eu-central-1.
• 10% of traffic is routed to ap-southeast-1.

Configuration Steps in Route 53

1. Create a new DNS record
   • Example: weighted.stephanetheteacher.com
   • Choose A Record type.
   • Set Routing Policy to Weighted.
2. Add individual records with different weights
   • Instance 1 (us-east-1) → Weight 70
   • Instance 2 (eu-central-1) → Weight 20
   • Instance 3 (ap-southeast-1) → Weight 10
3. Set a low TTL (Time to Live) value
   • In the demo, TTL is set to 3 seconds for quick testing.
   • In real-world applications, TTL should be higher to reduce unnecessary DNS lookups.
4. Associate optional health checks
   • Health checks ensure that traffic is not routed to unhealthy instances.
   • This feature will be covered in later lessons.

Use Cases for Weighted Routing