Tutorial: Using Lambda with Amazon SQS

In this tutorial, you create a Lambda function that consumes messages from an Amazon Simple Queue Service (Amazon SQS) queue.

Prerequisites

This tutorial assumes that you have some knowledge of basic Lambda operations and the Lambda console. If you haven't already, follow the instructions in Create a Lambda function with the console to create your first Lambda function.

To complete the following steps, you need a command line terminal or shell to run commands. Commands and the expected output are listed in separate blocks:

aws --version

You should see the following output:

aws-cli/2.0.57 Python/3.7.4 Darwin/19.6.0 exe/x86_64

For long commands, an escape character (\) is used to split a command over multiple lines.

On Linux and macOS, use your preferred shell and package manager. On Windows 10, you can install the Windows Subsystem for Linux to get a Windows-integrated version of Ubuntu and Bash.

Create the execution role

Create an execution role that gives your function permission to access the required AWS resources.

To create an execution role

1. Open the Roles page of the AWS Identity and Access Management (IAM) console.

2. Choose Create role.

3. Create a role with the following properties.

   • Trusted entity – AWS Lambda.

   • Permissions – AWSLambdaSQSQueueExecutionRole.

   • Role name – lambda-sqs-role.

The AWSLambdaSQSQueueExecutionRole policy has the permissions that the function needs to read items from Amazon SQS and to write logs to Amazon CloudWatch Logs.

Create the function

Create a Lambda function that processes your Amazon SQS messages. The following Node.js 12 code example writes each message to a log in CloudWatch Logs.

Note

For code examples in other languages, see Sample Amazon SQS function code.

Example index.js

exports.handler = async function(event, context) {
  event.Records.forEach(record => {
    const { body } = record;
    console.log(body);
  });
  return {};
}

To create the function

Note

Following these steps creates a function in Node.js 12. For other languages, the steps are similar, but some details are different.

1. Save the code example as a file named index.js.

2. Create a deployment package.

   zip function.zip index.js

3. Create the function using the create-function AWS Command Line Interface (AWS CLI) command.

   aws lambda create-function --function-name ProcessSQSRecord \
   --zip-file fileb://function.zip --handler index.handler --runtime nodejs12.x \
   --role arn:aws:iam::123456789012:role/lambda-sqs-role

Test the function

Invoke your Lambda function manually using the invoke AWS CLI command and a sample Amazon SQS event.

If the handler returns normally without exceptions, Lambda considers the message successfully processed and begins reading new messages in the queue. After successfully processing a message, Lambda automatically deletes it from the queue. If the handler throws an exception, Lambda considers the batch of messages not successfully processed, and Lambda invokes the function with the same batch of messages.

1. Save the following JSON as a file named input.txt.

   {
       "Records": [
           {
               "messageId": "059f36b4-87a3-44ab-83d2-661975830a7d",
               "receiptHandle": "AQEBwJnKyrHigUMZj6rYigCgxlaS3SLy0a...",
               "body": "test",
               "attributes": {
                   "ApproximateReceiveCount": "1",
                   "SentTimestamp": "1545082649183",
                   "SenderId": "AIDAIENQZJOLO23YVJ4VO",
                   "ApproximateFirstReceiveTimestamp": "1545082649185"
               },
               "messageAttributes": {},
               "md5OfBody": "098f6bcd4621d373cade4e832627b4f6",
               "eventSource": "aws:sqs",
               "eventSourceARN": "arn:aws:sqs:us-east-2:123456789012:my-queue",
               "awsRegion": "us-east-2"
           }
       ]
   }

   The preceding JSON simulates an event that Amazon SQS might send to your Lambda function, where "body" contains the actual message from the queue.

2. Run the following invoke AWS CLI command.

   aws lambda invoke --function-name ProcessSQSRecord \
   --payload file://input.txt outputfile.txt

   The cli-binary-format option is required if you are using AWS CLI version 2. You can also configure this option in your AWS CLI config file.

3. Verify the output in the file outputfile.txt.

Create an Amazon SQS queue

Create an Amazon SQS queue that the Lambda function can use as an event source.

To create a queue

1. Open the Amazon SQS console.

2. Choose Create queue, and then configure the queue. For detailed instructions, see Creating an Amazon SQS queue (console) in the Amazon Simple Queue Service Developer Guide.

3. After creating the queue, record its Amazon Resource Name (ARN). You need this in the next step when you associate the queue with your Lambda function.

Configure the event source

To create a mapping between your Amazon SQS queue and your Lambda function, run the following create-event-source-mapping AWS CLI command.

aws lambda create-event-source-mapping --function-name ProcessSQSRecord  --batch-size 10 \
--event-source-arn arn:aws:sqs:us-east-2:123456789012:my-queue

To get a list of your event source mappings, run the following command.

aws lambda list-event-source-mappings --function-name ProcessSQSRecord \
--event-source-arn arn:aws:sqs:us-east-2:123456789012:my-queue

Test the setup

Now you can test the setup as follows:

1. Open the Amazon SQS console.

2. Choose the name of the queue that you created earlier.

3. Choose Send and receive messages.

4. Under Message body, enter a test message.

5. Choose Send message.

Lambda polls the queue for updates. When there is a new message, Lambda invokes your function with this new event data from the queue. Your function runs and creates logs in Amazon CloudWatch. You can view the logs in the CloudWatch console.

Clean up your resources

You can now delete the resources that you created for this tutorial, unless you want to retain them. By deleting AWS resources that you're no longer using, you prevent unnecessary charges to your AWS account.

To delete the execution role

1. Open the Roles page of the IAM console.

2. Select the execution role that you created.

3. Choose Delete role.

4. Choose Yes, delete.

To delete the Lambda function

1. Open the Functions page of the Lambda console.

2. Select the function that you created.

3. Choose Actions, then choose Delete.

4. Choose Delete.

To delete the Amazon SQS queue

1. Sign in to the AWS Management Console and open the Amazon SQS console at https://console.aws.amazon.com/sqs/.

2. Select the queue you created.

3. Choose Delete.

4. Enter delete in the text box.

5. Choose Delete.