Tutorial: Creating a Lambda function with a function URL

In this tutorial, you create a Lambda function defined as a .zip file archive with a public function URL endpoint that returns the product of two numbers. For more information about configuring function URLs, see Creating and managing function URLs.

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 the AWS Command Line Interface (AWS CLI) version 2. 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.

Note

In Windows, some Bash CLI commands that you commonly use with Lambda (such as zip) are not supported by the operating system's built-in terminals. To get a Windows-integrated version of Ubuntu and Bash, install the Windows Subsystem for Linux. Example CLI commands in this guide use Linux formatting. Commands which include inline JSON documents must be reformatted if you are using the Windows CLI.

Create an execution role

Create the execution role that gives your Lambda function permission to access 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 – AWSLambdaBasicExecutionRole.

   • Role name – lambda-url-role.

The AWSLambdaBasicExecutionRole policy has the permissions that the function needs to write logs to Amazon CloudWatch Logs.

Create a Lambda function with a function URL (.zip file archive)

Create a Lambda function with a function URL endpoint using a .zip file archive.

To create the function

1. Copy the following code example into a file named index.js.

   Example index.js

   exports.handler = async (event) => {
       let body = JSON.parse(event.body)
       const product = body.num1 * body.num2;
       const response = {
           statusCode: 200,
           body: "The product of " + body.num1 + " and " + body.num2 + " is " + product,
       };
       return response;
   };

2. Create a deployment package.

   zip function.zip index.js

3. Create a Lambda function with the create-function command.

   aws lambda create-function \
       --function-name my-url-function \
       --runtime nodejs14.x \
       --zip-file fileb://function.zip \
       --handler index.handler \
       --role arn:aws:iam::123456789012:role/lambda-url-role

4. Add a resource-based policy to your function granting permissions to allow public access to your function URL.

   aws lambda add-permission \
       --function-name my-url-function \
       --action lambda:InvokeFunctionUrl \
       --principal "*" \
       --function-url-auth-type "NONE" \
       --statement-id url

5. Create a URL endpoint for the function with the create-function-url-config command.

   aws lambda create-function-url-config \
       --function-name my-url-function \
       --auth-type NONE

Test the function URL endpoint

Invoke your Lambda function by calling your function URL endpoint using an HTTP client such as curl or Postman.

curl -X POST \
    'https://abcdefg.lambda-url.us-east-1.on.aws/' \
    -H 'Content-Type: application/json' \
    -d '{"num1": "10", "num2": "10"}'

You should see the following output:

The product of 10 and 10 is 100

Create a Lambda function with a function URL (CloudFormation)

You can also create a Lambda function with a function URL endpoint using the AWS CloudFormation type AWS::Lambda::Url.

Resources:
  MyUrlFunction:
    Type: AWS::Lambda::Function
    Properties:
      Handler: index.handler
      Runtime: nodejs14.x
      Role: arn:aws:iam::123456789012:role/lambda-url-role
      Code:
        ZipFile: |
          exports.handler = async (event) => {
              let body = JSON.parse(event.body)
              const product = body.num1 * body.num2;
              const response = {
                  statusCode: 200,
                  body: "The product of " + body.num1 + " and " + body.num2 + " is " + product,
              };
              return response;
          };
      Description: Create a function with a URL.
  MyUrlFunctionPermissions:
    Type: AWS::Lambda::Permission
    Properties:
      FunctionName: !Ref MyUrlFunction
      Action: lambda:InvokeFunctionUrl
      Principal: "*"
      FunctionUrlAuthType: NONE
  MyFunctionUrl:
    Type: AWS::Lambda::Url
    Properties:
      TargetFunctionArn: !Ref MyUrlFunction
      AuthType: NONE

Create a Lambda function with a function URL (AWS SAM)

You can also create a Lambda function configured with a function URL using AWS Serverless Application Model (AWS SAM).

ProductFunction:
  Type: AWS::Serverless::Function
  Properties:
    CodeUri: function/.
    Handler: index.handler
    Runtime: nodejs14.x
    AutoPublishAlias: live
    FunctionUrlConfig:
      AuthType: NONE

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.

4. Enter the name of the role in the text input field and choose 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, Delete.

4. Type delete in the text input field and choose Delete.