Terraform interpolation to json file when json requires value to be integer

Question

Trying to work out if this is possible or not. Trawled terraform docs to no avail (not much surprise there).

Take the below extremely slim line example.

[
  {
    "cpu": "${var.master_container_cpu}",
  }
]

Adjoined to this tf parameter when invoking aws_ecs_task_definition resource;

container_definitions = "${file("task-definitions/example.json")}"

Will result in the following error;

Error: aws_ecs_task_definition.example-task: ECS Task Definition container_definitions is invalid: Error decoding JSON: json: cannot unmarshal string into Go struct field ContainerDefinition.Cpu of type int64

any help more than welcome :)

Answer 1

It looks like you should use a template to compile the JSON before using in the definition

data "template_file" "task" {
  template = "${file("${task-definitions/example.json")}"

  vars {
    cpu = "${var.master_container_cpu}"
  }
}

In the JSON file you can reference the var using ${cpu}

Then you are able to use the output as your definition

container_definitions = "${data.template_file.task.rendered}"