fishrock_lambda_http 0.3.0-patched.1

Application Load Balancer and API Gateway event types for AWS Lambda
Documentation 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172

#![warn(missing_docs)]
//#![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 optimiztions 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_runtime::run` in combination with the [`handler`](fn.handler.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::{handler, lambda_runtime::{self, Error}};
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Error> {
//!     // initialize dependencies once here for the lifetime of your
//!     // lambda task
//!     lambda_runtime::run(handler(|request, context| async { Ok("👋 world!") })).await?;
//!     Ok(())
//! }
//! ```
//!
//! ## Leveraging trigger provided data
//!
//! You can also access information provided directly from the underlying trigger events, like query string parameters,
//! with the [`RequestExt`](trait.RequestExt.html) trait.
//!
//! ```rust,no_run
//! use lambda_http::{handler, lambda_runtime::{self, Context, Error}, IntoResponse, Request, RequestExt};
//!
//! #[tokio::main]
//! async fn main() -> Result<(), Error> {
//!     lambda_runtime::run(handler(hello)).await?;
//!     Ok(())
//! }
//!
//! async fn hello(
//!     request: Request,
//!     _: Context
//! ) -> Result<impl IntoResponse, Error> {
//!     Ok(format!(
//!         "hello {}",
//!         request
//!             .query_string_parameters()
//!             .get("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};
pub use lambda_runtime::{self, Context};
use lambda_runtime::{Error, Handler as LambdaHandler};

mod body;
pub mod ext;
pub mod request;
#[doc(hidden)]
pub mod response;
mod strmap;
pub use crate::{body::Body, ext::RequestExt, response::IntoResponse, strmap::StrMap};
use crate::{
    request::{LambdaRequest, RequestOrigin},
    response::LambdaResponse,
};
use std::{
    future::Future,
    pin::Pin,
    task::{Context as TaskContext, Poll},
};

/// Type alias for `http::Request`s with a fixed [`Body`](enum.Body.html) type
pub type Request = http::Request<Body>;

/// Functions serving as ALB and API Gateway REST and HTTP API handlers must conform to this type.
///
/// This can be viewed as a `lambda_runtime::Handler` constrained to `http` crate `Request` and `Response` types
pub trait Handler: Sized {
    /// The type of Error that this Handler will return
    type Error;
    /// The type of Response this Handler will return
    type Response: IntoResponse;
    /// The type of Future this Handler will return
    type Fut: Future<Output = Result<Self::Response, Self::Error>> + Send + 'static;
    /// Function used to execute handler behavior
    fn call(&self, event: Request, context: Context) -> Self::Fut;
}

/// Adapts a [`Handler`](trait.Handler.html) to the `lambda_runtime::run` interface
pub fn handler<H: Handler>(handler: H) -> Adapter<H> {
    Adapter { handler }
}

/// An implementation of `Handler` for a given closure return a `Future` representing the computed response
impl<F, R, Fut> Handler for F
where
    F: Fn(Request, Context) -> Fut,
    R: IntoResponse,
    Fut: Future<Output = Result<R, Error>> + Send + 'static,
{
    type Response = R;
    type Error = Error;
    type Fut = Fut;
    fn call(&self, event: Request, context: Context) -> Self::Fut {
        (self)(event, context)
    }
}

#[doc(hidden)]
pub struct TransformResponse<R, E> {
    request_origin: RequestOrigin,
    fut: Pin<Box<dyn Future<Output = Result<R, E>> + Send>>,
}

impl<R, E> Future for TransformResponse<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.fut.as_mut().poll(cx) {
            Poll::Ready(result) => Poll::Ready(
                result.map(|resp| LambdaResponse::from_response(&self.request_origin, resp.into_response())),
            ),
            Poll::Pending => Poll::Pending,
        }
    }
}

/// Exists only to satisfy the trait cover rule for `lambda_runtime::Handler` impl
///
/// User code should never need to interact with this type directly. Since `Adapter` implements `Handler`
/// It serves as a opaque trait covering type.
///
/// See [this article](http://smallcultfollowing.com/babysteps/blog/2015/01/14/little-orphan-impls/)
/// for a larger explaination of why this is nessessary
pub struct Adapter<H: Handler> {
    handler: H,
}

impl<H: Handler> Handler for Adapter<H> {
    type Response = H::Response;
    type Error = H::Error;
    type Fut = H::Fut;
    fn call(&self, event: Request, context: Context) -> Self::Fut {
        self.handler.call(event, context)
    }
}

impl<H: Handler> LambdaHandler<LambdaRequest<'_>, LambdaResponse> for Adapter<H> {
    type Error = H::Error;
    type Fut = TransformResponse<H::Response, Self::Error>;

    fn call(&self, event: LambdaRequest<'_>, context: Context) -> Self::Fut {
        let request_origin = event.request_origin();
        let fut = Box::pin(self.handler.call(event.into(), context));
        TransformResponse { request_origin, fut }
    }
}