Amazon SNS

Amazon Simple Notification Service (SNS) implements the publish-subscribe messaging pattern. When you create an SNS topic, it becomes available for other services to subscribe to it. If someone publishes a message in this topic, all subscribed services will be alerted.

It's a very simple and powerful service. You can use it to dynamically attach different services that are able to handle a specific kind of notification. For example, an application can send a notification to an SNS topic to alert that you have received a new file to process. You can subscribe to this topic using an HTTP endpoint and SNS will send a message to your web service with the file location that needs processing. Later, you can add another endpoint, using a Lambda function programmed to do another kind of processing.

Let's perform the following steps to create a simple demo using the CLI as an example:

1. Create an SNS topic using the following command line:

        aws sns create-topic --name email-alerts

1. The result is an Amazon Resource Name (ARN) that you need to save. The ARN will be created with a format of this example: arn:aws:sns:us-east-1:1234567890:email-alerts
2. Subscribe to a topic using the e-mail protocol, so you will receive an e-mail every time that an application publishes to this topic:

        aws sns subscribe --topic-arn the_previous_arn --protocol email \
          --notification-endpoint myemail@example.com

1. Open your e-mail account and confirm that you want to subscribe to events.
2. Publish a test message and see it working by using the following command line:

        aws sns publish --topic-arn the_previous_arn --message "test"