AWS lambda function to find the latest Amazon AMI

find_latest_ami_name.py

"""
Publish the function to S3:

cd $DIR_WITH_THIS_SCRIPT
zip find_latest_ami_name.zip find_latest_ami_name.py
aws s3 cp find_latest_ami_name.zip s3://$YOUR_S3_BUCKET/find_latest_ami_name.zip
"""

import json

import boto3


ARCH_TO_AMI_NAME_PATTERN = {
    # Architecture: (pattern, owner)
    "PV64": ("amzn-ami-pv*.x86_64-ebs", "amazon"),
    "HVM64": ("amzn-ami-hvm*.x86_64-gp2", "amazon"),
    "HVMG2": ("amzn-ami-graphics-hvm-*x86_64-ebs*", "679593333241")
}


def find_latest_ami_name(region, arch):
    assert region, "Region is not defined"
    assert arch, "Architecture is not defined"
    assert arch in ARCH_TO_AMI_NAME_PATTERN, \
        "Architecture must be one of {}".format(
            ARCH_TO_AMI_NAME_PATTERN.keys())

    pattern, owner = ARCH_TO_AMI_NAME_PATTERN[arch]

    ec2 = boto3.client("ec2", region_name=region)

    images = ec2.describe_images(
        Filters=[dict(
            Name="name",
            Values=[pattern]
        )],
        Owners=[owner]
    ).get("Images", [])

    assert images, "No images were found"

    sorted_images = sorted(images, key=lambda image: image["Name"],
                           reverse=True)

    latest_image = sorted_images[0]

    return latest_image["ImageId"]


def handler(event, context):
    props = event.get("ResourceProperties", {})
    region = props.get("Region")
    arch = props.get("Architecture")
    return find_latest_ami_name(region, arch)


if __name__ == "__main__":
    print find_latest_ami_name("us-east-1", "HVM64")