New Load Balancer Target Group Rule not working

It seems like your new target group rules based on HTTP headers aren't working as expected. Here are a few things to check:

1. Listener Rules: Ensure that your Application Load Balancer (ALB) listener is correctly configured to route traffic based on the new header rules. Also, make sure the rule priority is correct and not overridden by others.

2. Target Group Health: Check that your instances in the target group are healthy. If they're unhealthy, traffic won’t be routed to them, even if the rule matches. You can verify the health in the Target Groups section in the EC2 console.

3. Header Matching: Double-check that the HTTP header you're using in the rule matches exactly what’s being sent in the requests. You can test this with tools like curl or Postman to ensure the headers are correct.

4. Target Group Port: Ensure the target group is set to listen on the correct port that your app is running on. Also, verify the security groups are set to allow traffic.

5. Logs: Enable ALB access logs to see how requests are being routed. This can give you insights into why traffic isn’t hitting the correct target group.

If you're still having issues, try simplifying your setup with a basic fixed response rule to test routing and ensure everything else is working.

For more info, you can check out these AWS resources:

• ALB Listener Rules
• Target Groups in ALB
• Health Checks for ALB

Let me know if this helps!

I apologize for the issue you're experiencing with your new Load Balancer Target Group rules. Based on the information provided, it seems there might be a few potential causes for the rules not working as expected. Let's explore some possibilities and steps to troubleshoot:

1. Listener Configuration: Ensure that the listener for your load balancer is properly configured to use the new rules. The rules should be associated with the correct listener.

2. Rule Order: Check the order of your rules in the listener. Rules are evaluated in order, so make sure your new rules are placed appropriately in the sequence.

3. Health Checks: Verify that the targets in your target group are passing health checks. If the targets are unhealthy, the load balancer won't route traffic to them.

4. Security Groups and Network ACLs: Confirm that the security groups and network ACLs associated with your load balancer and targets allow the necessary traffic.

5. Target Group Protocol and Port: Ensure that the protocol and port specified for the target group match those of your targets.

6. HTTP Header Configuration: Double-check that the HTTP header rule is correctly configured with the exact header name and value you're trying to match.

7. DNS Resolution: If you're using a custom domain, make sure it's correctly resolving to your load balancer's DNS name.

8. Target Registration: Verify that you have registered targets in your target group. Even if you're using an existing target group, ensure the targets are still registered and in service.

9. Load Balancer Logs: Enable access logs for your load balancer to get more detailed information about the requests and how they're being processed.

10. CloudWatch Metrics: Check CloudWatch metrics for your load balancer and target group to see if there are any unusual patterns or errors.

If you've confirmed all these points and are still experiencing issues, you may want to test with a simple rule (like a path-based rule) to isolate whether the problem is specific to the HTTP header matching or a more general configuration issue.

Remember, changes to load balancer rules may take a short time to propagate. If you've recently made changes, allow a few minutes for them to take effect.

If the problem persists after checking these items, you may need to contact AWS support for further assistance, as there could be an underlying issue with the load balancer or network configuration that requires deeper investigation.
Sources
Create a target group for your Application Load Balancer - Elastic Load Balancing
Troubleshoot your Application Load Balancers - Elastic Load Balancing