Docker – How to scale up one container using Amazon EC2 Container Service

I am new using Amazon ECS and I would like to know how to set up services in order to scale up / down one container easily.

Here is my project architecture:

• website: container with the website, only serving html pages and javascript/css/images. Listens on 80.
• api: container with the API developed in NodeJS serving json. Listens on 443.
• rabbitmq: container with rabbitmq. The api container is linked to it.
• worker: A container that waits for orders from rabbitmq (it is also linked to it) and process them, and then sends answers back to rabbitmq.

For now, I just created one task definition with all of my containers, and in my cluster I only have one service.
I also have a load balancer on the API (so I can access it from the website via a DNS name).

It works fine, but I want to be able to launch more workers , without launching everything else, and I don't seem to be able to do that right now (correct me if I'm wrong). So I have a few questions:

• Do I need to create separate task definitions?
• Do I need to create separate services?
• If I create a task definition for each container (thus front with website, back with api, broker with rabbitmq and worker with worker), am I still able to link containers together, even though they are not in the same task definition?

Here is my current task definition:

{
  "taskDefinitionArn": "arn:aws:ecs:ap-southeast-2:347930943102:task-definition/Flipendo:4",
  "revision": 4,
  "containerDefinitions": [
    {
      "volumesFrom": [],
      "portMappings": [],
      "command": [],
      "environment": [
      ],
      "essential": true,
      "entryPoint": [],
      "links": [
        "rabbitmq"
      ],
      "mountPoints": [],
      "memory": 2048,
      "name": "worker",
      "cpu": 4096,
      "image": "flipendo/worker"
    },
    {
      "volumesFrom": [],
      "portMappings": [],
      "command": [],
      "environment": [],
      "essential": true,
      "entryPoint": [],
      "links": [],
      "mountPoints": [],
      "memory": 2048,
      "name": "rabbitmq",
      "cpu": 2048,
      "image": "rabbitmq"
    },
    {
      "volumesFrom": [],
      "portMappings": [
        {
          "hostPort": 443,
          "containerPort": 3000
        }
      ],
      "command": [],
      "environment": [
      ],
      "essential": true,
      "entryPoint": [],
      "links": [
        "rabbitmq"
      ],
      "mountPoints": [],
      "memory": 2048,
      "name": "api",
      "cpu": 2048,
      "image": "flipendo/api"
    },
    {
      "volumesFrom": [],
      "portMappings": [
        {
          "hostPort": 80,
          "containerPort": 3000
        }
      ],
      "command": [],
      "environment": [
        {
          "name": "API_PORT",
          "value": "443"
        },
        {
          "name": "API_ADDR",
          "value": "load balancer dns server"
        }
      ],
      "essential": true,
      "entryPoint": [],
      "links": [
        "api"
      ],
      "mountPoints": [],
      "memory": 1024,
      "name": "website",
      "cpu": 1024,
      "image": "flipendo/website"
    }
  ],
  "volumes": [],
  "family": "Flipendo"
}

Thank you very much.