How can I update and ECS service adding an addition load balance to which a service talks to without downtime?

Question

We use terraform to manage our AWS resources and have the code to change the service from one to two load balancers.

However, terraform wants to destroy the service prior to recreating it. AWS cli docs indicate the reason - the API can only modify LBs during service creation and not on update.

• create-service
• update-service

It seems we need a blue/green deploy with the one LB and two LB services existing at the same time on the same cluster. I expect we'll need to create multiple task sets and the rest of the blue/green approach prior to this change (we'd planned for this anyway just not at this moment)

Does anyone have a good example for this scenario or know of any other approaches beyond full blue/green deployment?

Answer 1

Update 2022

ECS now supports updation of load balancers of a service. For now, this can be achieved using AWS CLI, AWS SDK, or AWS Cloudformation (not from AWS Console). From the documentation:

When you add, update, or remove a load balancer configuration, Amazon ECS starts new tasks with the updated Elastic Load Balancing configuration, and then stops the old tasks when the new tasks are running.

So, you don't need to create a new service. AWS update regarding this here. Please refer Update Service API doc on how to make the request.