Ahead of time scheduling on ECS/EC2: high_level.py

high_level.py

for asg in auto_scaling_groups:
  cluster_name = next(x for x in asg['Tags'] if x['Key'] == 'cluster_name')['Value']
  instance_list = ecs.list_container_instances(cluster=cluster_name, status='ACTIVE')
  instances = ecs.describe_container_instances(
      cluster=cluster_name, 
      containerInstances=instance_list['containerInstanceArns'])
  # all tasks running on current cluster
  tasks = get_tasks(cluster_name)
  # get the largest CPU reservation of any container
  max_cpu = int(max(tasks, key=lambda x: x['cpu'])['cpu'])
  # get the largest memory reservation of any container
  max_memory = int(max(tasks, key=lambda x: x['memory'])['memory'])
  schedulable_containers = 0
  for instance in instances['containerInstances']:
    remaining_resources = {resource['name']: resource 
                           for resource in instance['remainingResources']}
    # the amount of tasks that could be started based on CPU utilisation
    containers_by_cpu = int(remaining_resources['CPU']['integerValue'] / max_cpu)
    # the amount of tasks that could be started based on memory utilisation
    containers_by_mem = int(remaining_resources['MEMORY']['integerValue'] / max_memory)
    # the amount of containers that could be started on the current instance
    free_slots = min(containers_by_cpu, containers_by_mem)
    # add to the total of the cluster
    schedulable_containers += free_slots