How to make Lambda + API Gateway obey REQUEST_URI?

Question

I created an AWS Lambda with my application (a Web server) written in Rust Actix. I use https://crates.io/crates/lambda-web

Then I added this Lambda as the backend of an AWS HTTP API. The HTTP API has only `$default` stage.

https://XXX.execute-api.us-east-1.amazonaws.com/ produces correct result (what my packaged Web server outputs when the root is requested).

But https://XXX.execute-api.us-east-1.amazonaws.com/p/YYY produces: {"message":"Not Found"} what is surely not my Web server's output.

My task is to run the Web server in Lambda with path forwarded to the server in the normal way (as REQUEST_URI). So, when I request https://XXX.execute-api.us-east-1.amazonaws.com/p/YYY it should pass `/YYY` to my application. How?

Or probably it can be done with Lambda@Edge? Lambda@Edge follows the same protocol for Lambda as AWS HTTP API, doesn't it? In this case, there would be a CloudFront without origins, or what should I put as the origin, an arbitrary domain? Should Lambda@Edge be invoked on request or on response?

Answer

Look at [Proxy integrations](https://docs.aws.amazon.com/apigateway/latest/developerguide/http-api-develop-integrations-http.html). You need to define a greedy path using /{Proxy+}. This way you do not need to specify all routes in the API but rather specify one and let the Lambda function do the routing internally.

As an alternative you could create multiple routes and assign each one to a different function.

How to make Lambda + API Gateway obey REQUEST_URI?

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