ecs_describe_active_instances.py

import datetime
import itertools
import json

import boto3


REGION = 'us-east-1'
CLUSTER = 'what-the-fuck'
ECS_CLIENT = boto3.client('ecs', REGION)
REQUIRED_CPU_PER_TASK = 1024
REQUIRED_MEMORY_PER_TASK = 3500


def log(x):
    class Encoder(json.JSONEncoder):
        def default(self, o):
            if isinstance(o, datetime.datetime):
                return o.isoformat()

            return json.JSONEncoder.default(self, o)

    print(json.dumps(x, cls=Encoder))


def container_instance_arns(page_list):
    return [page['containerInstanceArns'] for page in page_list]


def get_active_instances(ecs, cluster):
    return ecs.get_paginator('list_container_instances').paginate(
        cluster=cluster, status='ACTIVE'
    )


def describe_container_instances(ecs, cluster, instance_arns):
    response = ecs.describe_container_instances(
        cluster=cluster,
        containerInstances=instance_arns)
    for i in response['containerInstances']:
        yield i


def describe_active_instances(ecs, cluster):
    page_list = get_active_instances(ecs, cluster)
    arns = [x for x in container_instance_arns(page_list) if x]
    desc = [describe_container_instances(ecs, cluster, x) for x in arns]
    return itertools.chain.from_iterable(desc)


def get_registered_cpu_and_memory(instance_description):
    cpu, memory = 0, 0
    for x in instance_description['registeredResources']:
        if x['name'] == 'CPU':
            cpu += x['integerValue']
        elif x['name'] == 'MEMORY':
            memory += x['integerValue']
    return cpu, memory


def calc_possible_tasks(cpu, memory, required_cpu, required_memory):
    by_cpu = cpu // required_cpu
    by_memory = memory // required_memory
    return by_cpu if by_cpu < by_memory else by_memory


def sum_possible_tasks(ecs, cluster, required_cpu, required_memory):
    possible_tasks = 0
    for i in describe_active_instances(ecs, cluster):
        cpu, memory = get_registered_cpu_and_memory(i)
        log({'cpu': cpu, 'memory': memory})
        possible_tasks += calc_possible_tasks(
            cpu, memory, required_cpu, required_memory
        )
    return possible_tasks


def foo(ecs, cluster, required_cpu, required_memory):
    tasks = sum_possible_tasks(ecs, cluster, required_cpu, required_memory)
    log(tasks)


foo(ECS_CLIENT, CLUSTER, REQUIRED_CPU_PER_TASK, REQUIRED_MEMORY_PER_TASK)