cloud-computing-msc-ai-examples/example-projects/tug-of-war-in-the-clouds/aws-boto3-standalone-db/create-loadbalancer.py

import boto3
from botocore.exceptions import ClientError

region = 'eu-central-1'
availabilityZone = 'eu-central-1b'
subnet1 = 'subnet-41422b28'
subnet2 = 'subnet-5c5f6d16'
subnet3 = 'subnet-6f2ea214'

client = boto3.setup_default_session(region_name=region)
ec2Client = boto3.client("ec2")
ec2Resource = boto3.resource('ec2')

response = ec2Client.describe_vpcs()
vpc_id = response.get('Vpcs', [{}])[0].get('VpcId', '')

response = ec2Client.describe_security_groups(Filters=[{'Name': 'group-name', 'Values': ['tug-of-war']}])
security_group_id = response.get('SecurityGroups', [{}])[0].get('GroupId', '')

elbv2Client = boto3.client('elbv2')

response = elbv2Client.create_load_balancer(
    Name='tug-of-war-loadbalancer',
    Subnets=[
        subnet1,
        subnet2,
        subnet3,
    ],
    SecurityGroups=[
        security_group_id
    ]
)

loadbalancer_arn = response.get('LoadBalancers', [{}])[0].get('LoadBalancerArn', '')
loadbalancer_dns = response.get('LoadBalancers', [{}])[0].get('DNSName', '')

response = elbv2Client.create_target_group(
    Name='tug-of-war-targetgroup',
    Port=80,
    Protocol='HTTP',
    VpcId=vpc_id,
)

targetgroup_arn = response.get('TargetGroups', [{}])[0].get('TargetGroupArn', '')

response = elbv2Client.create_listener(
    DefaultActions=[
        {
            'TargetGroupArn': targetgroup_arn,
            'Type': 'forward',
        },
    ],
    LoadBalancerArn=loadbalancer_arn,
    Port=80,
    Protocol='HTTP',
)

response = elbv2Client.modify_target_group_attributes(
    TargetGroupArn=targetgroup_arn,
    Attributes=[
        {
            'Key': 'stickiness.enabled',
            'Value': 'true'
        },
    ]
)

print("Registering instances...")
print("------------------------------------")

response = ec2Client.describe_instances(Filters=[{'Name': 'tag:tug-of-war', 'Values': ['webserver']}])
print(response)
reservations = response['Reservations']
for reservation in reservations:
    for instance in reservation['Instances']:
        if instance['State']['Name'] == "running" or instance['State']['Name'] == "pending":
            response = elbv2Client.register_targets(
                TargetGroupArn=targetgroup_arn,
                Targets=[
                    {
                        'Id': instance['InstanceId'],
                    },
                ],
            )

print('Waiting for Load Balancer to become available...')

waiter = elbv2Client.get_waiter('load_balancer_available')
waiter.wait(LoadBalancerArns=[loadbalancer_arn])
print('Load Balancer should be reachable at: ' + loadbalancer_dns)