An external data source for Terraform that returns the versions of all images in an ECS task definition

get_image_tags.py

''' Return image tags specified in ECS task definition '''
import json
import sys
import boto3

ECR_CLIENT = boto3.client('ecr')
ECS_CLIENT = boto3.client('ecs')


def main(cluster_name, service_name):
    '''The main routine'''

    image_versions = {}
    service = ECS_CLIENT.describe_services(
        cluster=cluster_name,
        services=[
            service_name
        ]
    )

    if not service['services']:
        # service doesn't exist yet, return empty dict
        return image_versions

    task_definition_arn = service['services'][0]['taskDefinition']
    task_definition = ECS_CLIENT.describe_task_definition(
        taskDefinition=task_definition_arn
    )

    for container in task_definition['taskDefinition']['containerDefinitions']:
        full_name = container['image'].split(':')
        # only add to response if image contains tag
        if len(full_name) > 1:
            image_versions[container['name']] = full_name[1]

    return image_versions


if __name__ == "__main__":
    args = json.load(sys.stdin)
    cluster_name = args['cluster_name']
    service_name = args['service_name']

    image_versions = main(cluster_name, service_name)
    print(json.dumps(image_versions))