Use an Application Load Balancer for Amazon ECS - Amazon Elastic Container Service

Use an Application Load Balancer for Amazon ECS

An Application Load Balancer makes routing decisions at the application layer (HTTP/HTTPS), supports path-based routing, and can route requests to one or more ports on each container instance in your cluster. Application Load Balancers support dynamic host port mapping. For example, if your task's container definition specifies port 80 for an NGINX container port, and port 0 for the host port, then the host port is dynamically chosen from the ephemeral port range of the container instance (such as 32768 to 61000 on the latest Amazon ECS-optimized AMI). When the task launches, the NGINX container is registered with the Application Load Balancer as an instance ID and port combination, and traffic is distributed to the instance ID and port corresponding to that container. This dynamic mapping allows you to have multiple tasks from a single service on the same container instance. For more information, see the User Guide for Application Load Balancers.

For information about the best practices for setting parameters to speed up you deployments see:

Consider the following when using Application Load Balancers with Amazon ECS:

  • Amazon ECS requires the service-linked IAM role which provides the permissions needed to register and deregister targets with your load balancer when tasks are created and stopped. For more information, see Using service-linked roles for Amazon ECS.

  • Target group must have the IP address type set to IPv4.

  • For services with tasks using the awsvpc network mode, when you create a target group for your service, you must choose ip as the target type, not instance. This is because tasks that use the awsvpc network mode are associated with an elastic network interface, not an Amazon EC2 instance.

  • If your service requires access to multiple load balanced ports, such as port 80 and port 443 for an HTTP/HTTPS service, you can configure two listeners. One listener is responsible for HTTPS that forwards the request to the service, and another listener that is responsible for redirecting HTTP requests to the appropriate HTTPS port. For more information, see Create a listener to your Application Load Balancer in the User Guide for Application Load Balancers.

  • Your load balancer subnet configuration must include all Availability Zones that your container instances reside in.

  • After you create a service, the load balancer configuration can't be changed from the AWS Management Console. You can use the AWS Copilot, AWS CloudFormation, AWS CLI or SDK to modify the load balancer configuration for the ECS rolling deployment controller only, not AWS CodeDeploy blue/green or external. When you add, update, or remove a load balancer configuration, Amazon ECS starts a new deployment with the updated Elastic Load Balancing configuration. This causes tasks to register to and deregister from load balancers. We recommend that you verify this on a test environment before you update the Elastic Load Balancing configuration. For information about how to modify the configuration, see UpdateService in the Amazon Elastic Container Service API Reference.

  • If a service task fails the load balancer health check criteria, the task is stopped and restarted. This process continues until your service reaches the number of desired running tasks.

  • If you are experiencing problems with your load balancer-enabled services, see Troubleshooting service load balancers in Amazon ECS.

  • Your tasks and load balancer must be in the same VPC.

  • Use a unique target group for each service.

    Using the same target group for multiple services might lead to issues during service deployments.

For information about how to create an Application Load Balancer, see Create an Application Load Balancer in Application Load Balancers