[AWS Lab] Lambda Invocation via Polling – SQS

In this lab, we will learn how a lambda function can be invoked via Polling.

• Overview
• Source: SQS
  • Create a queue and a dead-letter queue (DLQ)
• Target: Lambda – Function
  • logs the received message
  • does not return any value
  • configures the trigger
  • Python

1. IAM – Setup the Lambda execution role

• Click “Roles” on the left pane
• Click “Create role“
• Select trusted entity
  • Trusted entity type: “AWS service“
  • Use: “Lambda“
• Add Permissions
  • Search “AWSLambdaSQSQueueExecutionRole” and select it
• Name, review
  • Name: “LambdaSQSExecutionRole“
• Click “Create role“

Lambda service needs to poll SQS. Therefore you need to provide the execution permission to the Lambda function.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "sqs:ReceiveMessage",
                "sqs:DeleteMessage",
                "sqs:GetQueueAttributes",
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents"
            ],
            "Resource": "*"
        }
    ]
}

2. Lambda – Create a Function

• Function Name: “logMessage“
• Runtime: Python 3.9
• Permissions
  • Check “Use an existing role“
  • Select “LambdaSQSExecutionRole“
  • Click “Create function“

3. Lambda – Function Code (Python)

• Type the following code
• Click “Deploy“

import json
import logging

logger = logging.getLogger()
logger.setLevel(logging.INFO)

def lambda_handler(event, context):
    logger.info(json.dumps(event))

4. SQS – Create a dead-letter queue

• Click “Create queue”
  • Select “Standard”
  • Name: “my-dlq“
• Click “Create queue“

5. SQS – Create a queue

• Click “Create queue”
  • Select “Standard”
  • Name: “greeting-queue“
• Under the “Dead-letter queue”
  • Check “Enabled“
  • Select the dead-letter queue “my-dlq“
  • Maximum receives: 2
• Click “Create queue“

6. SQS – Test the Dead-letter queue

1. Click the “Queues” menu on the left pane
2. Select the newly created queue “greeting-queue“
3. Click “Send and receive messages“
4. Enter any message text and send it –> send 2 more messages
5. In the “Receive messages” section, you can see the “Messages available” count -> 3
6. Click “Poll for messages” three times
   • The messages will be removed.
7. Move to the dead-letter queue and check the messages.

7. Lambda – Configure the SQS as a Lambda trigger

1. On the “logMessage” function page, “Function overview” -> “Add trigger“
2. Select “SQS” as a source
3. Select the “greeting-queue“
4. Click “Add“

8. SQS- Test

1. On the “greeting-queue” page, click “Send and receive messages“
2. Enter any message text and send it

9. CouldWatch – Check the Lambda logs

1. On the Lambda function page, click the “Monitor” tab
2. Check some metrics on the page
3. Click the “View logs in the CloudWatch” button
4. On the CloudWatch page, click the “Log stream“
5. Check the logs