Using SNS and SQS fan-out messages

Services Covered

•  SQS
•  SNS

Lab description

In this lab, you will implement the backbone of a fan-out order messaging scenario using Amazon Simple Notification Service (SNS) and Amazon Simple Queue Service (SQS). Messages are published to an Amazon SNS topic and then pushed to Amazon SQS subscriber queues. This eliminates the need for periodic polling and allows for messages to be processed in parallel asynchronously by the subscribers.

Learning Objectives

• Create a Fan-Out pattern for messages
• Use SNS ans SQS for processing messages
• Use AWS CLI on EC2 to publish and receive messages

Lab date

04-12-2021

Prerequisites

• AWS account

Lab steps

1. In the SNS dashboard create a topic, choose the standard one. In the Access policy section, under Define who can publish messages to the topic, select Everyone. For Define who can subscribe to this topic, select Everyone. This Amazon SNS topic is where orders are published to. In a non-lab environment it would most likely be a web application or other application that accepts orders that will publish messages to this topic.
   
2. Navigate to SQS Dashboard and create two standard queues. First one might be named order-for-inventory with default configuration. Second one called orders-for-analytics will be similar with default settings.
3. Subscribe the orders-for-analytics queue to previously created topic
   
   Repeat the topic subscription process for your orders-for-inventory Amazon SQS queue.
4. Navigate to EC2 and launch an t3.micro instance with Security Group allowing SSH access to it. The instance will also need an IAM role that has permissions to interact with Amazon SNS topic and SQS queues. Then connect to it using EC2 Instance Connect or SSH client. In the terminal window enter following command:

   aws sns list-topics

   

5. To publish a message, enter the following, replacing <YOUR-TOPIC-ARN> with the ARN you listed in a previous instruction:

   aws sns publish 
   --topic-arn <YOUR-TOPIC-ARN> 
   --message  "1 x Widget @ 21.99 USDn2 x Widget Cables @ 5.99 USD"

   

6. To list Amazon Simple Queue Service queues, enter the following command:

   aws sqs list-queues

   

7. To retrieve a message from the orders-for-analytics queue, enter the following command, replacing <YOUR-ANALYTICS-QUEUE-URL>

   aws sqs receive-message 
      --queue-url <YOUR-ANALYTICS-QUEUE-URL>

   

8. Repeat the previous instruction, using the orders-for-inventory queue.
9. To delete a message, enter the following command for the orders-for-inventory queue or the second one.

   aws sqs delete-message 
      --queue-url <YOUR-QUEUE-URL> 
      --receipt-handle <YOUR-RECEIPT-HANDLE>

Lab files

Acknowledgements

• cloud academy