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#![warn(missing_docs, rust_2018_idioms)]
//#![deny(warnings)]
//! Enriches the `lambda` crate with [`http`](https://github.com/hyperium/http)
//! types targeting AWS [ALB](https://docs.aws.amazon.com/elasticloadbalancing/latest/application/introduction.html), [API Gateway](https://docs.aws.amazon.com/apigateway/latest/developerguide/welcome.html) REST and HTTP API lambda integrations.
//!
//! This crate abstracts over all of these trigger events using standard [`http`](https://github.com/hyperium/http) types minimizing the mental overhead
//! of understanding the nuances and variation between trigger details allowing you to focus more on your application while also giving you to the maximum flexibility to
//! transparently use whichever lambda trigger suits your application and cost optimizations best.
//!
//! # Examples
//!
//! ## Hello World
//!
//! The following example is how you would structure your Lambda such that you have a `main` function where you explicitly invoke
//! `lambda_http::run` in combination with the [`service_fn`](fn.service_fn.html) function. This pattern allows you to utilize global initialization
//! of tools such as loggers, to use on warm invokes to the same Lambda function after the first request, helping to reduce the latency of
//! your function's execution path.
//!
//! ```rust,no_run
//! use lambda_http::{service_fn, Error};
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Error> {
//! // initialize dependencies once here for the lifetime of your
//! // lambda task
//! lambda_http::run(service_fn(|request| async {
//! Result::<&str, std::convert::Infallible>::Ok("👋 world!")
//! })).await?;
//! Ok(())
//! }
//! ```
//!
//! ## Leveraging trigger provided data
//!
//! You can also access information provided directly from the underlying trigger events,
//! like query string parameters, or Lambda function context, with the [`RequestExt`] trait.
//!
//! ```rust,no_run
//! use lambda_http::{service_fn, Error, RequestExt, IntoResponse, Request};
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Error> {
//! lambda_http::run(service_fn(hello)).await?;
//! Ok(())
//! }
//!
//! async fn hello(
//! request: Request
//! ) -> Result<impl IntoResponse, std::convert::Infallible> {
//! let _context = request.lambda_context_ref();
//!
//! Ok(format!(
//! "hello {}",
//! request
//! .query_string_parameters_ref()
//! .and_then(|params| params.first("name"))
//! .unwrap_or_else(|| "stranger")
//! ))
//! }
//! ```
// only externed because maplit doesn't seem to play well with 2018 edition imports
#[cfg(test)]
#[macro_use]
extern crate maplit;
pub use http::{self, Response};
/// Utilities to initialize and use `tracing` and `tracing-subscriber` in Lambda Functions.
#[cfg(feature = "tracing")]
pub use lambda_runtime::tracing;
pub use lambda_runtime::{self, service_fn, tower, Context, Error, LambdaEvent, Service};
use request::RequestFuture;
use response::ResponseFuture;
mod deserializer;
pub mod ext;
pub mod request;
mod response;
pub use crate::{
ext::{RequestExt, RequestPayloadExt},
response::IntoResponse,
};
use crate::{
request::{LambdaRequest, RequestOrigin},
response::LambdaResponse,
};
// Reexported in its entirety, regardless of what feature flags are enabled
// because working with many of these types requires other types in, or
// reexported by, this crate.
pub use aws_lambda_events;
pub use aws_lambda_events::encodings::Body;
use std::{
future::Future,
marker::PhantomData,
pin::Pin,
task::{Context as TaskContext, Poll},
};
mod streaming;
pub use streaming::run_with_streaming_response;
/// Type alias for `http::Request`s with a fixed [`Body`](enum.Body.html) type
pub type Request = http::Request<Body>;
/// Future that will convert an [`IntoResponse`] into an actual [`LambdaResponse`]
///
/// This is used by the `Adapter` wrapper and is completely internal to the `lambda_http::run` function.
#[doc(hidden)]
pub enum TransformResponse<'a, R, E> {
Request(RequestOrigin, RequestFuture<'a, R, E>),
Response(RequestOrigin, ResponseFuture),
}
impl<'a, R, E> Future for TransformResponse<'a, R, E>
where
R: IntoResponse,
{
type Output = Result<LambdaResponse, E>;
fn poll(mut self: Pin<&mut Self>, cx: &mut TaskContext<'_>) -> Poll<Self::Output> {
match *self {
TransformResponse::Request(ref mut origin, ref mut request) => match request.as_mut().poll(cx) {
Poll::Ready(Ok(resp)) => {
*self = TransformResponse::Response(origin.clone(), resp.into_response());
self.poll(cx)
}
Poll::Ready(Err(err)) => Poll::Ready(Err(err)),
Poll::Pending => Poll::Pending,
},
TransformResponse::Response(ref mut origin, ref mut response) => match response.as_mut().poll(cx) {
Poll::Ready(resp) => Poll::Ready(Ok(LambdaResponse::from_response(origin, resp))),
Poll::Pending => Poll::Pending,
},
}
}
}
/// Wraps a `Service<Request>` in a `Service<LambdaEvent<Request>>`
///
/// This is completely internal to the `lambda_http::run` function.
#[doc(hidden)]
pub struct Adapter<'a, R, S> {
service: S,
_phantom_data: PhantomData<&'a R>,
}
impl<'a, R, S, E> From<S> for Adapter<'a, R, S>
where
S: Service<Request, Response = R, Error = E>,
S::Future: Send + 'a,
R: IntoResponse,
{
fn from(service: S) -> Self {
Adapter {
service,
_phantom_data: PhantomData,
}
}
}
impl<'a, R, S, E> Service<LambdaEvent<LambdaRequest>> for Adapter<'a, R, S>
where
S: Service<Request, Response = R, Error = E>,
S::Future: Send + 'a,
R: IntoResponse,
{
type Response = LambdaResponse;
type Error = E;
type Future = TransformResponse<'a, R, Self::Error>;
fn poll_ready(&mut self, cx: &mut core::task::Context<'_>) -> core::task::Poll<Result<(), Self::Error>> {
self.service.poll_ready(cx)
}
fn call(&mut self, req: LambdaEvent<LambdaRequest>) -> Self::Future {
let request_origin = req.payload.request_origin();
let event: Request = req.payload.into();
let fut = Box::pin(self.service.call(event.with_lambda_context(req.context)));
TransformResponse::Request(request_origin, fut)
}
}
/// Starts the Lambda Rust runtime and begins polling for events on the [Lambda
/// Runtime APIs](https://docs.aws.amazon.com/lambda/latest/dg/runtimes-api.html).
///
/// This takes care of transforming the LambdaEvent into a [`Request`] and then
/// converting the result into a [`LambdaResponse`].
pub async fn run<'a, R, S, E>(handler: S) -> Result<(), Error>
where
S: Service<Request, Response = R, Error = E>,
S::Future: Send + 'a,
R: IntoResponse,
E: std::fmt::Debug + std::fmt::Display,
{
lambda_runtime::run(Adapter::from(handler)).await
}
#[cfg(test)]
mod test_adapter {
use std::task::{Context, Poll};
use crate::{
http::{Response, StatusCode},
lambda_runtime::LambdaEvent,
request::LambdaRequest,
response::LambdaResponse,
tower::{util::BoxService, Service, ServiceBuilder, ServiceExt},
Adapter, Body, Request,
};
// A middleware that logs requests before forwarding them to another service
struct LogService<S> {
inner: S,
}
impl<S> Service<LambdaEvent<LambdaRequest>> for LogService<S>
where
S: Service<LambdaEvent<LambdaRequest>>,
{
type Response = S::Response;
type Error = S::Error;
type Future = S::Future;
fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
self.inner.poll_ready(cx)
}
fn call(&mut self, event: LambdaEvent<LambdaRequest>) -> Self::Future {
// Log the request
println!("Lambda event: {event:#?}");
self.inner.call(event)
}
}
/// This tests that `Adapter` can be used in a `tower::Service` where the user
/// may require additional middleware between `lambda_runtime::run` and where
/// the `LambdaEvent` is converted into a `Request`.
#[test]
fn adapter_is_boxable() {
let _service: BoxService<LambdaEvent<LambdaRequest>, LambdaResponse, http::Error> = ServiceBuilder::new()
.layer_fn(|service| {
// This could be any middleware that logs, inspects, or manipulates
// the `LambdaEvent` before it's converted to a `Request` by `Adapter`.
LogService { inner: service }
})
.layer_fn(Adapter::from)
.service_fn(|_event: Request| async move { Response::builder().status(StatusCode::OK).body(Body::Empty) })
.boxed();
}
}