ced949cb6b
Until this commit, servers have required that `Service` and their `Future` to be `Send`, since the server needs to spawn some internal tasks to an executor, and by default, that is `tokio::spawn`, which could be spawning to a threadpool. This was true even if the user were certain there was no threadpool involved, and was instead using a different single-threaded runtime, like `tokio::runtime::current_thread`. This changes makes all the server pieces generic over an `E`, which is essentially `Executor<PrivateTypes<Server::Future>>`. There's a new set of internal traits, `H2Exec` and `NewSvcExec`, which allow for the type signature to only show the generics that the user is providing. The traits cannot be implemented explicitly, but there are blanket implementations for `E: Executor<SpecificType>`. If the user provides their own executor, it simply needs to have a generic `impl<F> Executor<F> for MyExec`. That impl can have bounds deciding whether to require `F: Send`. If the executor does require `Send`, and the `Service` futures are `!Send`, there will be compiler errors. To prevent a breaking change, all the types that gained the `E` generic have a default type set, which is the original `tokio::spawn` executor.
52 lines
1.3 KiB
Rust
52 lines
1.3 KiB
Rust
#![deny(warnings)]
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extern crate futures;
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extern crate hyper;
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extern crate pretty_env_logger;
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extern crate tokio;
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use std::cell::Cell;
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use std::rc::Rc;
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use hyper::{Body, Response, Server};
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use hyper::service::service_fn_ok;
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use hyper::rt::Future;
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use tokio::runtime::current_thread;
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fn main() {
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pretty_env_logger::init();
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let addr = ([127, 0, 0, 1], 3000).into();
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// Using a !Send request counter is fine on 1 thread...
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let counter = Rc::new(Cell::new(0));
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let new_service = move || {
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// For each connection, clone the counter to use in our service...
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let cnt = counter.clone();
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service_fn_ok(move |_| {
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let prev = cnt.get();
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cnt.set(prev + 1);
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Response::new(Body::from(format!("Request count: {}", prev + 1)))
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})
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};
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// Since the Server needs to spawn some background tasks, we needed
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// to configure an Executor that can spawn !Send futures...
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let exec = current_thread::TaskExecutor::current();
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let server = Server::bind(&addr)
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.executor(exec)
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.serve(new_service)
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.map_err(|e| eprintln!("server error: {}", e));
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println!("Listening on http://{}", addr);
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current_thread::Runtime::new()
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.expect("rt new")
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.spawn(server)
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.run()
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.expect("rt run");
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}
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