Controller.py

import boto3
from Sqs_utils import get_queue_length
from ec2_utils import create_new_instance, terminate_instance

def control():
    Access_key_ID = 'AKIARULFMIFKR62ZIRNX'
    Secret_access_key = '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'

    ec2 = boto3.resource('ec2', region_name='us-east-1',
                        aws_access_key_id=Access_key_ID, 
                        aws_secret_access_key=Secret_access_key)


    worker_names = ['worker-1','worker-2','worker-3','worker-4','worker-5','worker-6','worker-7','worker-8','worker-9','worker-10','worker-11','worker-12','worker-13','worker-14', 'worker-15', 'worker-16', 'worker-17','worker-18','worker-19']
    current_workers = set()

    web_tier_instance = set(["i-006eff98f4ca14aac", "i-05b326253e4bb6a9a"])

    states = ["running" , "stopped" , "pending"]

    running_instances = []
    start_and_pending = 0
    for instance in ec2.instances.all():
        if instance.id not in web_tier_instance and instance.state['Name'] == "running" or instance.state['Name'] == "pending":
            try:
                current_workers.add(instance.tags[0]['Value'])
            except:
                pass
            start_and_pending +=1
                
        if instance.id != web_tier_instance and instance.state['Name'] == "running":
                running_instances.append(instance.id)

    available_names = [i  for i in worker_names if i not in current_workers]
            

    length_of_queue = get_queue_length()
    if length_of_queue == 0:
        #print("Here")
        if len(running_instances) > 0:
            terminate_instance(running_instances.pop())
        else:
            pass
    else:
        ideal_number_of_instaces = min( max(1,length_of_queue// 4) , 19)
        if start_and_pending < ideal_number_of_instaces:
            start_instances = ideal_number_of_instaces - start_and_pending
            for i in range(start_instances):
                if len(available_names)> 0:
                        resp = create_new_instance(available_names.pop(0))
                else:
                        resp = create_new_instance("Some Worker")
        
        elif start_and_pending == ideal_number_of_instaces:
            pass
        
        else:
            if len(running_instances) > 0:
                terminate_instance(running_instances.pop())
            else:
                pass