Update EC2 tags for instances in an Auto Scaling Group

README.md

update-tags.py

Update EC2 tags for instances in an Auto Scaling Group.

When changing the tags for an Auto Scaling Group, these changes only apply to new instances launched. Therefore, you need something to apply the new tags to existing instances.

update-tags.py

import boto3

ASG_NAME = "replace-me"
TAGS = [
    {
        "Key": "foo",
        "Value": "bar",
    },
]

def get_instances(asg_name):
    client = boto3.client('autoscaling')
    response = client.describe_auto_scaling_groups(AutoScalingGroupNames=[asg_name])
    assert len(response["AutoScalingGroups"]) == 1
    asg = response["AutoScalingGroups"][0]
    instances = asg["Instances"]
    return list(i["InstanceId"] for i in instances)

def update_tags(instance_ids, tags):
    client = boto3.client('ec2')
    client.create_tags(
        Resources=instance_ids,
        Tags=tags,
    )

if __name__ == "__main__":
    instances = get_instances(ASG_NAME)
    update_tags(instances, TAGS)
    print(f"{len(instances)} instances updated")