Terraform 是否公开 ECS 启动类型中使用的 EC2 实例的实例 ID？

Question

I'm deploying an app to an ECS cluster with an EC2 launch type. I've had some success here, and have stood up a load balancer in front of the cluster, and the instance receives and responds to traffic fine.

For a separate task, I'm also looking at being able to individually address the instance, which Terraform lets me do if I've got the instance ID, but I don't see the instance ID being one of the data outputs of aws_launch_configuration .

Is there a way to extract the instance ID of an EC2 instance used in an ECS cluster?

Answer 1

You can do this by using the aws_instance data source

In it, you can specify a few filters to retrieve any EC2 instance.

For example, let's say that your launch configuration (by the way, you should use a launch template, it's "launch configuration v2" basically with more features) assigns some tags to your ECS Container Instance, one of them being Name:ECSClusterX . Knowing this you can retrieve the said EC2 instance by:

data "aws_instance" "ecs-instance" {
  filter {
    name   = "tag:Name"
    values = ["ECSClusterX"]
  }
}

then you can retrieve the id of the found instance, by: aws_instance.ecs-instance.id .

That's it, you are all set!

Answer 2

If you are looking for launch a task in a specific instances, a good practice is using attributes.

In your cluster, move to the ECS Instances tab, then select one instance. Open the Actions menu like in the picture and go to View/Edit Attributes :

Add your attribute:

The last step is to configure your task definition in your terraform.

resource "aws_ecs_task_definition" "component1" {
    ...
    placement_constraints {
      type = "memberOf"
      expression =  "attribute:deploy_type == standard"
    }
    ...
}

Now the task only will be executed in the instances that match the attribute.

I use lambda function to keep all the time at least one instance with the each attribute block that I need. But you can integrate instances to the cluster with different launch templates and different attributes.