Blocked ports and autoscaling group in aws

Question

I have an autoscaling group with the following settings:

- name: configure auto-scaling group
      ec2_asg:
        name: "{{ application_name }}-{{ application_environment }}-auto-scaling-group"
        availability_zones:
          - "{{ region }}a"
          - "{{ region }}b"
          - "{{ region }}c"
        state: present
        launch_config_name: "{{ application_name }}-{{ application_environment }}-launch-configuration"
        min_size: 1
        max_size: 2
        region: "{{ region }}"
        desired_capacity: 2
        tags:
          - environment: "{{application_environment}}"
        vpc_zone_identifier:
          - "{{ vpc.subnets[0].id }}"
          - "{{ vpc.subnets[1].id }}"
          - "{{ vpc.subnets[2].id }}"

It's spinning up two ec2 instances.

On both instances, there is a service running with an nginx listening to port 80. I understand that I cannot use port 80 twice. The service has a desired capacity of 2, but I'm willing to have one running during rolling-updates.

However, if i update the service and task definition, I get the following error:

ERROR: (service myapp-testing-service) was unable to place a task because no container instance met all of its requirements. The closest matching (container-instance 24d9d97e-c979-41a3-a438-212390612ae3) is already using a port required by your task. For more information, see the Troubleshooting section of the Amazon ECS Developer Guide.

It's true, the port is blocked. What I want to happen in that case is that one nginx-service is taken down, the new is taken up, the other one is taken down after that and replaced with the new one.

I thought that this is the default behaviour, but it looks like it isn't - or do I get something wrong?

Answer 1

You will need to reconfigure your ECS service configuration for myapp-testing-service.

Set the Minimum healthy percent to 50.

This will allow your service to RUN 1 task of the old version when deploying the new version.