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router.to_async(), simple async/.await examples #281
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[package] | ||
name = "gotham_examples_handlers_simple_async_handlers_await" | ||
description = "An example that does asynchronous work before responding" | ||
version = "0.0.0" | ||
authors = ["David Laban <alsuren@gmail.com>"] | ||
publish = false | ||
edition = "2018" | ||
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[dependencies] | ||
gotham = { path = "../../../gotham" } | ||
gotham_derive = { path = "../../../gotham_derive" } | ||
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mime = "0.3.16" | ||
futures = "0.3.1" | ||
serde = "1.0.104" | ||
serde_derive = "1.0.104" | ||
tokio = "0.2.9" |
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# Async Request Handlers (.await version) | ||
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The idea of async handlers has already been introduced by the post_handler example in | ||
[Request Data](../request_data), which waits for the POST body asyncronously, and resolves | ||
the response future once it has processed the body. The combinator-based version | ||
of this example can be found at [Async Request Handlers](../simple_async_handlers). | ||
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This example has exactly the same behavior and API as the combinator-based version, | ||
and it can be used as a reference when converting your code to use async/await. | ||
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## Running | ||
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From the `examples/handlers/async_handlers` directory: | ||
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``` | ||
Terminal 1: | ||
Compiling gotham_examples_handlers_simple_async_handlers v0.0.0 (file:///.../gotham/examples/handlers/simple_async_handlers) | ||
Finished dev [unoptimized + debuginfo] target(s) in 8.19 secs | ||
Running `.../gotham/target/debug/gotham_examples_handlers_simple_async_handlers` | ||
Listening for requests at http://127.0.0.1:7878 | ||
sleep for 5 seconds once: starting | ||
sleep for 5 seconds once: finished | ||
sleep for one second 5 times: starting | ||
sleep for one second 5 times: finished | ||
Terminal 2: | ||
$ curl 'http://127.0.0.1:7878/sleep?seconds=5' | ||
slept for 5 seconds | ||
$ curl 'http://127.0.0.1:7878/loop?seconds=5' | ||
slept for 1 seconds | ||
slept for 1 seconds | ||
slept for 1 seconds | ||
slept for 1 seconds | ||
slept for 1 seconds | ||
``` | ||
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## License | ||
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Licensed under your option of: | ||
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* [MIT License](../../LICENSE-MIT) | ||
* [Apache License, Version 2.0](../../LICENSE-APACHE) | ||
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## Community | ||
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The following policies guide participation in our project and our community: | ||
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* [Code of conduct](../../CODE_OF_CONDUCT.md) | ||
* [Contributing](../../CONTRIBUTING.md) |
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//! A basic example showing the request components | ||
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use futures::prelude::*; | ||
use std::pin::Pin; | ||
use std::time::{Duration, Instant}; | ||
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use gotham::hyper::{Body, StatusCode}; | ||
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use gotham::handler::HandlerResult; | ||
use gotham::helpers::http::response::create_response; | ||
use gotham::router::builder::DefineSingleRoute; | ||
use gotham::router::builder::{build_simple_router, DrawRoutes}; | ||
use gotham::router::Router; | ||
use gotham::state::{FromState, State}; | ||
use gotham_derive::{StateData, StaticResponseExtender}; | ||
use serde_derive::Deserialize; | ||
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use tokio::time::delay_until; | ||
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type SleepFuture = Pin<Box<dyn Future<Output = Vec<u8>> + Send>>; | ||
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#[derive(Deserialize, StateData, StaticResponseExtender)] | ||
struct QueryStringExtractor { | ||
seconds: u64, | ||
} | ||
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/// Sneaky hack to make tests take less time. Nothing to see here ;-). | ||
#[cfg(not(test))] | ||
fn get_duration(seconds: u64) -> Duration { | ||
Duration::from_secs(seconds) | ||
} | ||
#[cfg(test)] | ||
fn get_duration(seconds: u64) -> Duration { | ||
Duration::from_millis(seconds) | ||
} | ||
/// All this function does is return a future that resolves after a number of | ||
/// seconds, with a Vec<u8> that tells you how long it slept for. | ||
/// | ||
/// Note that it does not block the thread from handling other requests, because | ||
/// it returns a `Future`, which will be managed by the tokio reactor, and | ||
/// called back once the timeout has expired. | ||
/// | ||
/// Vec<u8> is chosen because it is one of the things that you need to resolve | ||
/// a HandlerFuture and respond to a request. | ||
/// | ||
/// Most things that you call to access remote services (e.g databases and | ||
/// web apis) can be coerced into returning futures that yield useful data, | ||
/// so the patterns that you learn in this example should be applicable to | ||
/// real world problems. | ||
fn sleep(seconds: u64) -> SleepFuture { | ||
let when = Instant::now() + get_duration(seconds); | ||
let delay = delay_until(when.into()).map(move |_| { | ||
format!("slept for {} seconds\n", seconds) | ||
.as_bytes() | ||
.to_vec() | ||
}); | ||
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delay.boxed() | ||
} | ||
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/// This handler sleeps for the requested number of seconds, using the `sleep()` | ||
/// helper method, above. | ||
async fn sleep_handler(mut state: State) -> HandlerResult { | ||
let seconds = QueryStringExtractor::take_from(&mut state).seconds; | ||
println!("sleep for {} seconds once: starting", seconds); | ||
// Here, we call the sleep function and turn its old-style future into | ||
// a new-style future. Note that this step doesn't block: it just sets | ||
// up the timer so that we can use it later. | ||
let sleep_future = sleep(seconds); | ||
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// Here is where the serious sleeping happens. We yield execution of | ||
// this block until sleep_future is resolved. | ||
// The Ok("slept for x seconds") value is stored in result. | ||
let data = sleep_future.await; | ||
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// Here, we convert the result from `sleep()` into the form that Gotham | ||
// expects: `state` is owned by this block so we need to return it. | ||
// We also convert any errors that we have into the form that Hyper | ||
// expects, using the helper from IntoHandlerError. | ||
let res = create_response(&state, StatusCode::OK, mime::TEXT_PLAIN, data); | ||
println!("sleep for {} seconds once: finished", seconds); | ||
Ok((state, res)) | ||
} | ||
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/// It calls sleep(1) as many times as needed to make the requested duration. | ||
/// | ||
/// Notice how much easier it is to read than the version in | ||
/// `simple_async_handlers`. | ||
async fn loop_handler(mut state: State) -> HandlerResult { | ||
let seconds = QueryStringExtractor::take_from(&mut state).seconds; | ||
println!("sleep for one second {} times: starting", seconds); | ||
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// The code within this block reads exactly like syncronous code. | ||
// This is the style that you should aim to write your business | ||
// logic in. | ||
let mut accumulator = Vec::new(); | ||
for _ in 0..seconds { | ||
let body = sleep(1).await; | ||
accumulator.extend(body) | ||
} | ||
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let res = create_response( | ||
&state, | ||
StatusCode::OK, | ||
mime::TEXT_PLAIN, | ||
Body::from(accumulator), | ||
); | ||
println!("sleep for one second {} times: finished", seconds); | ||
Ok((state, res)) | ||
} | ||
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/// Create a `Router`. | ||
fn router() -> Router { | ||
build_simple_router(|route| { | ||
route | ||
.get("/sleep") | ||
.with_query_string_extractor::<QueryStringExtractor>() | ||
.to_async(sleep_handler); | ||
route | ||
.get("/loop") | ||
.with_query_string_extractor::<QueryStringExtractor>() | ||
.to_async(loop_handler); | ||
}) | ||
} | ||
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/// Start a server and use a `Router` to dispatch requests. | ||
pub fn main() { | ||
let addr = "127.0.0.1:7878"; | ||
println!("Listening for requests at http://{}", addr); | ||
gotham::start(addr, router()) | ||
} | ||
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#[cfg(test)] | ||
mod tests { | ||
use gotham::test::TestServer; | ||
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use super::*; | ||
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fn assert_returns_ok(url_str: &str, expected_response: &str) { | ||
let test_server = TestServer::new(router()).unwrap(); | ||
let response = test_server.client().get(url_str).perform().unwrap(); | ||
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assert_eq!(response.status(), StatusCode::OK); | ||
assert_eq!( | ||
&String::from_utf8(response.read_body().unwrap()).unwrap(), | ||
expected_response | ||
); | ||
} | ||
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#[test] | ||
fn sleep_says_how_long_it_slept_for() { | ||
assert_returns_ok("http://localhost/sleep?seconds=2", "slept for 2 seconds\n"); | ||
} | ||
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#[test] | ||
fn loop_breaks_the_time_into_one_second_sleeps() { | ||
assert_returns_ok( | ||
"http://localhost/loop?seconds=2", | ||
"slept for 1 seconds\nslept for 1 seconds\n", | ||
); | ||
} | ||
} |
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use crate::extractor::{PathExtractor, QueryStringExtractor}; | ||
use crate::handler::assets::{DirHandler, FileHandler, FileOptions, FilePathExtractor}; | ||
use crate::handler::{Handler, NewHandler}; | ||
use crate::handler::{Handler, HandlerResult, NewHandler}; | ||
use crate::pipeline::chain::PipelineHandleChain; | ||
use crate::router::builder::{ | ||
ExtendRouteMatcher, ReplacePathExtractor, ReplaceQueryStringExtractor, SingleRouteBuilder, | ||
}; | ||
use crate::router::route::dispatch::DispatcherImpl; | ||
use crate::router::route::matcher::RouteMatcher; | ||
use crate::router::route::{Delegation, Extractors, RouteImpl}; | ||
use crate::state::State; | ||
use core::future::Future; | ||
use futures::FutureExt; | ||
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/// Describes the API for defining a single route, after determining which request paths will be | ||
/// dispatched here. The API here uses chained function calls to build and add the route into the | ||
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where | ||
H: Handler + RefUnwindSafe + Copy + Send + Sync + 'static; | ||
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/// Similar to `to`, but accepts an `async fn` | ||
/// | ||
/// # Examples | ||
/// | ||
/// ```rust | ||
/// # extern crate gotham; | ||
/// # extern crate hyper; | ||
/// # | ||
/// # use hyper::{Body, Response, StatusCode}; | ||
/// # use gotham::handler::HandlerResult; | ||
/// # use gotham::state::State; | ||
/// # use gotham::router::Router; | ||
/// # use gotham::router::builder::*; | ||
/// # use gotham::pipeline::new_pipeline; | ||
/// # use gotham::pipeline::single::*; | ||
/// # use gotham::middleware::session::NewSessionMiddleware; | ||
/// # use gotham::test::TestServer; | ||
/// # | ||
/// async fn my_handler(state: State) -> HandlerResult { | ||
/// // Handler implementation elided. | ||
/// # Ok((state, Response::builder().status(StatusCode::ACCEPTED).body(Body::empty()).unwrap())) | ||
/// } | ||
/// # | ||
/// # fn router() -> Router { | ||
/// # let (chain, pipelines) = single_pipeline( | ||
/// # new_pipeline().add(NewSessionMiddleware::default()).build() | ||
/// # ); | ||
/// | ||
/// build_router(chain, pipelines, |route| { | ||
/// route.get("/request/path").to_async(my_handler); | ||
/// }) | ||
/// # | ||
/// # } | ||
/// # | ||
/// # fn main() { | ||
/// # let test_server = TestServer::new(router()).unwrap(); | ||
/// # let response = test_server.client() | ||
/// # .get("https://example.com/request/path") | ||
/// # .perform() | ||
/// # .unwrap(); | ||
/// # assert_eq!(response.status(), StatusCode::ACCEPTED); | ||
/// # } | ||
/// ``` | ||
fn to_async<H, Fut>(self, handler: H) | ||
where | ||
Self: Sized, | ||
H: (FnOnce(State) -> Fut) + RefUnwindSafe + Copy + Send + Sync + 'static, | ||
Fut: Future<Output = HandlerResult> + Send + 'static, | ||
{ | ||
self.to_new_handler(move || Ok(move |s: State| handler(s).boxed())) | ||
} | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I have implemented this directly on the trait because it feels like the most backwards-compatible thing to do. In practice, the only implementation of DefineSingleRoute in the gotham codebase is SingleRouteBuilder. Would you rather I implement it on SingleRouteBuilder and force all external implementors of DefineSingleRoute to implement it? Also, can someone look extra-hard at the marker traits that I've used on There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I'm not sure. In a world where you don't care about backwards compatibility, which would you go for? The versioning model we are on allows us to break things, and we can provide documentation for migration if it's complicated. The traits seem ok to me (when looking at a diff). I feel like There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Ideally, the We can take it one step forward and disallow the mapping to There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. If both future fn and async fn could not be supported at the same time and we are willing to break, then we should give priority to async fn and create a new There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. @whitfin that sounds like the right question to ask. Good thinking. In an ideal world, I would probably think about making this trait private or something (I think that a recent compiler release that allows traits to be marked nonexhaustive, so they can't be implemented by external people?). In the short term, "program to the interface" seems to be the pattern that's being used here, so refactoring the implementation down into SingleRouteBuilder sounds like the thing to do. I will add this to the checklist, and do it once I have all of the other questions worked out. @pksunkara: (I think that this is a separate discussion) as it stands in my PR (using your terminology) I can pass a "future fn" to When I wrote this, I didn't think it's possible to create a single function that can accept both an I've been mulling it over in my head over the last couple of days, and I think that it might be possible to impl Future for There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
:( There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. How about making the return object There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. same deal: HandlerResult is just a Result that's generic over tuples, so it' also foreign.
I think that we need a separate There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more.
I had a quick play about and I couldn't see a way to get rid of them. The handler callback is
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/// Directs the route to the given `NewHandler`. This gives more control over how `Handler` | ||
/// values are constructed. | ||
/// | ||
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I believe this link is incorrect as it points to itself if I'm not mistaken
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Good spot. Thanks.