Q45 - What is Lambda Function URL? #serverless #url #aws #cloudcomputing #awslambda #awsservice

A function URL is a dedicated HTTP(S) endpoint for your Lambda function. You can create and configure a function URL through the Lambda console or the Lambda API. When you create a function URL, Lambda automatically generates a unique URL endpoint for you. Once you create a function URL, its URL endpoint never changes. Function URL endpoints have the following format:

Function URLs are dual stack-enabled, supporting IPv4 and IPv6. After you configure a function URL for your function, you can invoke your function through its HTTP(S) endpoint via a web browser, curl, Postman, or any HTTP client.

Note
You can access your function URL through the public Internet only. While Lambda functions do support AWS PrivateLink, function URLs do not.

Lambda function URLs use resource-based policies for security and access control. Function URLs also support cross-origin resource sharing (CORS) configuration options.

You can apply function URLs to any function alias, or to the $LATEST unpublished function version. You can't add a function URL to any other function version.

You can use AWS CloudTrail and Amazon CloudWatch to monitor your function URLs.

Function URL invocation basics

If your function URL uses the AWS_IAM auth type, you must sign each HTTP request using AWS Signature Version 4 (SigV4). Tools such as awscurl, Postman, and AWS SigV4 Proxy offer built-in ways to sign your requests with SigV4.

If you don't use a tool to sign HTTP requests to your function URL, you must manually sign each request using SigV4. When your function URL receives a request, Lambda also calculates the SigV4 signature. Lambda processes the request only if the signatures match. For instructions on how to manually sign your requests with SigV4, see Signing AWS requests with Signature Version 4 in the Amazon Web Services General Reference Guide.

If your function URL uses the NONE auth type, you don't have to sign your requests using SigV4. You can invoke your function using a web browser, curl, Postman, or any HTTP client.

To test other HTTP requests, such as a POST request, you can use a tool such as curl. For example, if you want to include some JSON data in a POST request to your function URL, you could use the following curl command:

-H 'content-type: application/json' \
-d '{ "example": "test" }'