listen_topic.py

# This script will listen to a given topic at the localstack and print the messages in 20 seconds

import sys
import boto3


region = 'us-west-2'
queue_name = 'listening-queue'
queue_arn = f'arn:aws:sqs:{region}:000000000000:{queue_name}'
queue_url = f'http://localhost:4566/000000000000/{queue_name}'


sns = boto3.client('sns', region_name=region, endpoint_url='http://localhost:4566')
sqs = boto3.client('sqs', region_name=region, endpoint_url='http://localhost:4566')


def assure_queue_exists(name):
    sqs.create_queue(QueueName=name)


def assure_subscription(topic_arn):
    sns.subscribe(TopicArn=topic_arn, Protocol='sqs',
                  Endpoint=queue_arn)


def assure_topic(name):
    sns.create_topic(Name=name)


def get_messages():
    result = sqs.receive_message(QueueUrl=queue_url, WaitTimeSeconds=20)
    for message in result.get('Messages', []):
        sqs.delete_message(QueueUrl=queue_url, ReceiptHandle=message['ReceiptHandle'])
        yield message['Body']


def setup(topic_name):
    assure_topic(topic_name)
    assure_queue_exists(queue_name)
    topic_arn = f'arn:aws:sns:{region}:000000000000:{topic_name}'
    assure_subscription(topic_arn)


def main(topic_name):
    setup(topic_name)
    for message in get_messages():
        print(message)


if __name__ == "__main__":
    if len(sys.argv) < 2:
        topic_to_listen = input("Topic Name:")
    else:
        topic_to_listen = sys.argv[1]
    main(topic_to_listen)