Achieving Path-Based Routing with AWS Application Load Balancer: A Step-by-Step Guide

In this tutorial, I’m going to demonstrate how you can achieve path-based routing on an Application Load Balancer (ALB). Path-based routing allows you to direct incoming requests to specific target groups based on the URL path. It’s a powerful feature that enables you to host multiple services or microservices behind a single ALB, each responding to different URL paths.

Prerequisites

Before we begin, make sure you have completed the following prerequisites:

1. Launch EC2 Instances: Launch Amazon EC2 instances and deploy the microservices you want to route based on URL paths. In this example, I’ve launched instances for “Service A,” “Service B” (for /path1/*), “Service C,” and “Service D” (for /path2/*).

Now, let’s dive into the step-by-step process of setting up path-based routing with an ALB.

Creating Target Groups

1. Log in to AWS Console: Log in to your AWS account and navigate to the AWS Management Console.
2. Select Region: Ensure that you are in the same AWS region where you have launched your EC2 instances.
3. Navigate to Target Groups: On the navigation pane, under “Load Balancing,” select “Target Groups.”
4. Create Target Group: Create a target group for the first set of targets (e.g., /path1). Click “Create target group.”
5. Configure Target Group: Provide a name (e.g., “TargetGroup1”), specify the protocol, port (e.g., 80), and the VPC for the target group. Then, click “Create.”
6. Register Targets: Select the new target group, go to the “Targets” tab, and click “Edit.” Choose the instances (e.g., “Service A” and “Service B”) that run the microservice for /path1. Specify the port for the instances, click “Add to registered,” and then click “Save.”
7. Create Another Target Group: Repeat steps 4-6 to create a second target group (e.g., “TargetGroup2”) for /path2 and register instances (e.g., “Service C” and “Service D”) that run the microservice for /path2.

Configuring Path-Based Routing

1. ALB Listeners: Go to the Application Load Balancer’s “Listeners” tab and select the listener where you want to set up path-based routing.
2. Edit Rules: Click “View/Edit Rules” to configure routing rules.
3. Add Rules: Click the “Add Rules” icon to add rules for path-based routing.
4. Define Rule for /path1: To route requests for /path1 to TargetGroup1, specify the rule as follows:
   • Click “Insert Rule.”
   • Choose “Add Condition,” select “Path is,” and enter /path1.
   • Click the checkmark icon to save the condition.
   • Choose “Add Action,” select “Forward to,” and then choose TargetGroup1 that you created earlier.
   • Click the checkmark icon to save the action.
   • Click “Save” to save the rule.
5. Define Rule for /path2: Repeat step 4 to create a rule for /path2 and forward it to TargetGroup2.
6. Save Rules: You can have similar rules for other listeners defined on your load balancer. Click “Save” to save the rules.

And that’s it! You’ve successfully set up path-based routing on an Application Load Balancer. Now, requests to /path1 will be directed to TargetGroup1, and requests to /path2 will be directed to TargetGroup2.

Conclusion

Path-based routing with AWS Application Load Balancer is a powerful way to efficiently route incoming requests to different microservices or services running on your EC2 instances. This feature helps you maintain a clean and organized application architecture while utilizing a single ALB. I hope this step-by-step guide helps you configure path-based routing effectively for your AWS infrastructure.