this will delete an existing ami and creates new ami from a specific instance, creates new instance from newly created ami and attached it to load balancer

boto3_scaling_ec2.py

import boto3
import time

region = 'us-east-1'
image_name = "image_name"
instance_id = "i-0777a5dc8892fbdbb"
elb_name = 'elb'
instance_type = 't2.micro'
instance_tag_name = 'Friendly_Name'
AZ_name = 'us-east-1b'
SECURITY_GROUP_ID = 'sg-2a45d85c'
INSTANCE_SUBNET_ID = 'subnet-65c5ee3f'


###################### DELETING IMAGE IF EXISTS ####################
####################################################################
client = boto3.client('ec2', region_name=region)

print("FINDING AND REPLACING THE EXISTING IMAGE...")
response = client.describe_images(
    Filters=[
        {
            'Name': 'name',
            'Values': [
                image_name,
            ]
        },
    ],
    Owners=['self'],
)
print(response)

for image in response['Images']:
    ami_id = image['ImageId']
    print("IMAGE_ID: " + ami_id)

    if ami_id in image['ImageId']:
        print("DELETING IMAGE")
        client.deregister_image(ImageId=ami_id)


time.sleep(240)



########################## CREATING IMAGE ###########################
#####################################################################
ec2client = boto3.client('ec2', region_name=region)

print("CREATING IMAGE FROM INSTANCE " + instance_id)
createAMI = ec2client.create_image(
       InstanceId = instance_id,
       Name = image_name,
       Description = image_name,
       NoReboot = True)
imageID = []
imageID.append(createAMI)
def getImageId(imageID):
    for i in imageID:
        newami = i['ImageId']
        return newami

newImageId = getImageId(imageID)
print("IMAGE_ID: " + newImageId)

waiter = ec2client.get_waiter('image_available')   ######## WAIT UNTIL IMAGE IS AVAILABLE
waiter.wait(
    Filters=[
        {
            'Name': 'state',
            'Values': ['available']
        },
    ],
    ImageIds=[newImageId],
    Owners=['self']
)


######################### CREATING INSTANCE #########################
#####################################################################
ec2=boto3.resource('ec2', region_name=region)

print("CREATING INSTANCE FROM THE IMAGE_ID...")
instance = ec2.create_instances(
    ImageId=newImageId,
    MinCount=1,
    MaxCount=1,
    InstanceType=instance_type,
    KeyName='new-vargin',
    Monitoring={'Enabled': False},
    Placement={'AvailabilityZone': AZ_name,
               'Tenancy': 'default'},
    SecurityGroupIds=[SECURITY_GROUP_ID],
    SubnetId=INSTANCE_SUBNET_ID,
    EbsOptimized=False,
    TagSpecifications=[{'ResourceType': 'instance',
                        'Tags': [{'Key': 'Name',
                                  'Value': instance_tag_name}]
    }],
    #IamInstanceProfile={'Name': 'your_IAM_role'}
    )

new_instance_id = instance[0].id
print("NEW INSTANCE ID " + new_instance_id)
ec2_client=boto3.client('ec2', region_name=region)           ######## WAIT UNTIL INSTANCE IS AVAILABLE
waiter=ec2_client.get_waiter('instance_running')
waiter.wait(InstanceIds=[instance[0].instance_id])




############################ CREATING ALARM ##########################
#####################################################################

cloudwatch = boto3.client('cloudwatch', region_name=region)

# Create alarm with actions enabled
cloudwatch.put_metric_alarm(
    AlarmName='Server_LOW_CPU_Utilization',
    ComparisonOperator='LessThanThreshold',
    EvaluationPeriods=1,
    MetricName='CPUUtilization',
    Namespace='AWS/EC2',
    Period=300,
    Statistic='Average',
    Threshold=30.0,
    ActionsEnabled=True,
    AlarmActions=[
      'arn:aws:automate:us-east-1:ec2:terminate'
    ],
    AlarmDescription='Alarm when server CPU exceeds 30%',
    Dimensions=[
        {
          'Name': 'InstanceId',
          'Value': new_instance_id
        },
    ],
    # Unit='Seconds'
)




########################## ATTATCH TO ELB ###########################
#####################################################################
print("ATTATCHING CREATED INSTANCE " + new_instance_id + "UNDER ELB " + elb_name)
client = boto3.client('elb', region_name=region)
response = client.describe_load_balancers(
    LoadBalancerNames=[elb_name],
)
#print(response)

response = client.register_instances_with_load_balancer(
    Instances=[
        {
            'InstanceId': new_instance_id,
        },
    ],
    LoadBalancerName=elb_name,
)
print(response)

print("INSTANCE ATTATCHED...")



# ################# ATTATCH TO ALB ######################
# #######################################################
# client = boto3.client('elbv2', region_name=region)
#
# print("PLACE THE INSTANCE BEHIND THE APPLICATION LOAD BALANCER...")
# response = client.register_targets(
#     TargetGroupArn='TARGET_GROUP_ARN',
#     Targets=[
#         {
#             'Id': new_instance_id,
#         },
#     ]
# )
# print(response)