Fetch env-file from AWS ECS Service TD (Task Definition)

fetch-aws-ecs-env.py

#!/usr/bin/env python3
import argparse
import datetime
import sys
import os.path

import boto3
import jinja2


MAIN_TEMPLATE = """
# Env-file for AWS ECS service {{ service }} in cluster {{ cluster }}
# describing Task Definition {{ td.taskDefinitionArn }}
#
# Generated by {{ myname }} on {{ timestamp }} -- DO NOT EDIT

{% for container in td.containerDefinitions %}
#-- Container  {{ container.name }}
#-- from image {{ container.image }}
{% for envitem in container.environment|sort(attribute="name") %}
{{ envitem.name }}={{ envitem.value }}
{% endfor %}
{% endfor %}

""".strip()


def main(opts):
    ecs = boto3.client("ecs")

    svc = ecs.describe_services(cluster=opts.cluster, services=[opts.service])
    svc = svc["services"]
    if not svc:
        return "Empty response, check service name"
    assert len(svc) == 1
    [svc] = svc

    td = ecs.describe_task_definition(taskDefinition=svc["taskDefinition"])
    td = td["taskDefinition"]

    tmpl = jinja2.Environment(trim_blocks=True).from_string(MAIN_TEMPLATE)
    print(
        tmpl.render(
            myname=os.path.basename(__file__),
            timestamp=datetime.datetime.now().isoformat(),
            cluster=opts.cluster,
            service=opts.service,
            td=td,
        )
    )


if __name__ == "__main__":
    argP = argparse.ArgumentParser(
        description="Fetch ECS service environment as an env-file"
    )
    argP.add_argument("cluster", help="which ECS cluster")
    argP.add_argument("service", help="which service in the cluster")
    opts = argP.parse_args()
    sys.exit(main(opts))