I have an AWS cluster which is running multiple tasks, each of these being a revision of the previous one as these revisions are identical except for a path change the docker command passed to them. I wanted to automate this process using Terraform. I want to create a new revision of an existing task, and run a new task in an existing cluster which picks this latest task revision. But right now I am only able to create a new task definition and a new ECS cluster everytime I am running the script. I am not sure what I am missing.

Here are the relevant sections of my script

# main.tf

# Provider configuration
provider "aws" {
  region = "ap-northeast-1"
}

# Read input.yaml file
data "local_file" "input" {
  filename = "input.yaml"
}

# Parse input.yaml file
locals {
  input_data = yamldecode(data.local_file.input.content)
}

# Retrieve existing ECS task definition
data "aws_ecs_task_definition" "existing_task" {
  task_definition = "modbus-simulator-fargate-task"
}

# Create new ECS task definition based on existing one with modifications
resource "aws_ecs_task_definition" "modbus_simulator" {
  family                   = data.aws_ecs_task_definition.existing_task.family
  task_role_arn            = data.aws_ecs_task_definition.existing_task.task_role_arn
  execution_role_arn       = data.aws_ecs_task_definition.existing_task.execution_role_arn
  network_mode             = data.aws_ecs_task_definition.existing_task.network_mode
  requires_compatibilities = ["FARGATE"]  # Add FARGATE here
  cpu                      = 1024      # Specify CPU here
  memory                   = 3072       # Specify memory here

  container_definitions = jsonencode([
    {
      "name": "client-server-simulator",
      "image": "337039605624.dkr.ecr.ap-northeast-1.amazonaws.com/client-server-simulator:26-june-2024",
      "cpu": 0,
      "portMappings": [
        {
          "name": "client-server-simulator-80-tcp",
          "containerPort": 80,
          "hostPort": 80,
          "protocol": "tcp",
          "appProtocol": "http"
        }
      ],
      "essential": true,
      "command": [
        "--s3-path",
        local.input_data[0].s3_path,
        "--modbus-ip",
        local.input_data[0].modbus_ip,
        "--modbus-port",
        local.input_data[0].modbus_port,
        "--interval",
        local.input_data[0].interval,
        "--edge-id",
        local.input_data[0].edge_id,
        "--location",
        local.input_data[0].location,
        "--company",
        local.input_data[0].company
      ],
      "environment": [],
      "mountPoints": [],
      "volumesFrom": [],
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "/ecs/modbus-simulator-fargate-task",
          "awslogs-create-group": "true",
          "awslogs-region": "ap-northeast-1",
          "awslogs-stream-prefix": "ecs"
        }
      },
      "systemControls": []
    }
  ])
}

# Update ECS service to use the new task definition revision
resource "aws_ecs_service" "modbus_simulator_service" {
  name            = "modbus-simulator-service"
  cluster         = "modbus-simulator-cluster" # use the existing cluster
  task_definition = aws_ecs_task_definition.modbus_simulator.arn
  desired_count   = 1

  # Update only if there's a change in the task definition
  lifecycle {
    ignore_changes = [task_definition]
  }
}

I have tried going through the examples provided in the repository.