AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH does not ignore stage in API Gateway V2 (HTTP)

[artemudovyk]

The AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH env variable doesn't seem to work on API Gateway V2 (HTTP).

Example:

use axum::{response::Json, routing::get, Router};
use lambda_http::request::RequestContext::ApiGatewayV2;
use lambda_http::{run, tracing, Error};
use serde_json::{json, Value};

// Sample middleware that logs the request id
async fn mw_sample(
    req: axum::extract::Request,
    next: axum::middleware::Next,
) -> impl axum::response::IntoResponse {
    let context = req
        .extensions()
        .get::<lambda_http::request::RequestContext>();
    if let Some(ApiGatewayV2(ctx)) = context {
        tracing::info!("RequestId = {:?}", ctx);
    }
    next.run(req).await
}

async fn handler_sample() -> Json<Value> {
    Json(json!({ "echo":  "hello" }))
}

#[tokio::main]
async fn main() -> Result<(), Error> {
    std::env::set_var("AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH", "true"); // ignore stages in routing

    tracing::init_default_subscriber();

    let app = Router::new()
        .route("/not-staged", get(handler_sample)) // stage not specified, not working
        .route("/v1/staged", get(handler_sample)) // stage specified, working
        .layer(axum::middleware::from_fn(mw_sample));

    run(app).await
}

Cargo.toml:

[package]
name = "test"
version = "0.1.0"
edition = "2021"

[dependencies]
axum = "0.7.5"
lambda_http = "0.13.0"
serde = "1.0.209"
serde_json = "1.0.127"
tokio = { version = "1", features = ["macros"] }

I will attach my Terraform code as well:

module "api_lambda_function" {
  source = "terraform-aws-modules/lambda/aws"

  function_name = "some-api"

  runtime       = "provided.al2023"
  architectures = ["arm64"]
  timeout       = 15

  create_package         = false
  // Change path to your bin
  local_existing_package = "../../../target/lambda/simple2/bootstrap.zip"
  handler                = "bootstrap"

  create_current_version_allowed_triggers = false
  allowed_triggers = {
    AllowExecutionFromAPIGateway = {
      service    = "apigateway"
      source_arn = "${aws_apigatewayv2_api.main.execution_arn}/*"
    }
  }
}

resource "aws_apigatewayv2_api" "main" {
  name          = "${local.name_prefix}-api"
  protocol_type = "HTTP"
}

resource "aws_apigatewayv2_stage" "v1" {
  api_id      = aws_apigatewayv2_api.main.id
  name        = "v1"
  auto_deploy = true
}

resource "aws_apigatewayv2_integration" "api_lambda" {
  api_id                 = aws_apigatewayv2_api.main.id
  integration_type       = "AWS_PROXY"
  integration_method     = "POST"
  integration_uri        = module.api_lambda_function.lambda_function_arn
  payload_format_version = "2.0"
  depends_on             = [module.api_lambda_function.lambda_function_arn]
}

resource "aws_apigatewayv2_route" "get_1" {
  api_id    = aws_apigatewayv2_api.main.id
  route_key = "GET /not-staged"
  target    = "integrations/${aws_apigatewayv2_integration.api_lambda.id}"
}

resource "aws_apigatewayv2_route" "get_2" {
  api_id    = aws_apigatewayv2_api.main.id
  route_key = "GET /staged"
  target    = "integrations/${aws_apigatewayv2_integration.api_lambda.id}"
}

Build with:

cargo lambda build --release --arm64 --output-format zip

And then apply Terraform.

When calling a /v1/staged route, response is returned:

But not for /v1/not-staged - response is 404:

Am I doing something wrong?
Can someone please suggest how to debug this issue?

[jfkisafk]

It seems this is where the env_variable is handled:

aws-lambda-rust-runtime/lambda-http/src/request.rs

Lines 367 to 385 in 6228204

	#[cfg(any(feature = "apigw_rest", feature = "apigw_http", feature = "apigw_websockets"))]
	fn apigw_path_with_stage(stage: &Option<String>, path: &str) -> String {
	if env::var("AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH").is_ok() {
	return path.into();
	}
	let stage = match stage {
	None => return path.into(),
	Some(stage) if stage == "$default" => return path.into(),
	Some(stage) => stage,
	};
	let prefix = format!("/{stage}/");
	if path.starts_with(&prefix) {
	path.into()
	} else {
	format!("/{stage}{path}")
	}
	}

1. Can you please indicated which request payload format version are you using 1.0 or 2.0? -> it is 2.0 based on your terraform.
2. Also, can you confirm if you have tried setting the env variable AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH in your Lambda Function configuration (through terraform) and it still doesn't work?

[calavera]

I think there is a misconception on what this variable is for.

If the variable is not set, and your lambda event has a stage in the JSON payload, the runtime will add the stage to the path, so the function code receives the full path that APIGW received, in your case v1 + staged.

If the variable is set, the runtime will not add the stage to the path.

However, if your path includes the stage directly, like /v1/not-staged, the runtime, will not remove the stage from the path.

I hope that makes sense.

[artemudovyk]

Thank you.

2. Also, can you confirm if you have tried setting the env variable AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH in your Lambda Function configuration (through terraform) and it still doesn't work?

Yes, I've also tried to apply an env variable with Terraform — it behaved the same.

However, if your path includes the stage directly, like /v1/not-staged, the runtime, will not remove the stage from the path.

Yes, I understand. I don't expect it to remove the stage from the specified route. I've used both prefixed and unprefixed routes for demonstration purposes. In my example, the /not-staged you mentioned is specified without a /v1/ prefix, which doesn't work with the env variable in question is set.

I would expect that the configuration:

  std::env::set_var("AWS_LAMBDA_HTTP_IGNORE_STAGE_IN_PATH", "true");

  let app = Router::new()
      .route("/route1", get(handler_sample))
      .route("/route2", get(handler_sample));

could handle any stage in the API Gateway (/v1/route1, /v2/route1, /route1 etc.), but I've only got 404 responses from Lambda (not from API Gateway) instead. This configuration only works for me on the $default stage (without prefix).

[moranbw]

I am seeing the same behavior as @artemudovyk for API Gateway V2. Don't mean to create a +1 comment, but just wanted to see if this was going to be addressed of if there is anything we can do to help.