1use std::future::Future;
2
3/// An asynchronous function from a `Request` to a `Response`.
4///
5/// The `Service` trait is a simplified interface making it easy to write
6/// network applications in a modular and reusable way, decoupled from the
7/// underlying protocol.
8///
9/// # Functional
10///
11/// A `Service` is a function of a `Request`. It immediately returns a
12/// `Future` representing the eventual completion of processing the
13/// request. The actual request processing may happen at any time in the
14/// future, on any thread or executor. The processing may depend on calling
15/// other services. At some point in the future, the processing will complete,
16/// and the `Future` will resolve to a response or error.
17///
18/// At a high level, the `Service::call` function represents an RPC request. The
19/// `Service` value can be a server or a client.
20pub trait Service<Request> {
21 /// Responses given by the service.
22 type Response;
23
24 /// Errors produced by the service.
25 ///
26 /// Note: Returning an `Error` to a hyper server, the behavior depends on the
27 /// protocol. In most cases, hyper will cause the connection to be abruptly aborted.
28 /// It will abort the request however the protocol allows, either with some sort of RST_STREAM,
29 /// or killing the connection if that doesn't exist.
30 type Error;
31
32 /// The future response value.
33 type Future: Future<Output = Result<Self::Response, Self::Error>>;
34
35 /// Process the request and return the response asynchronously.
36 /// `call` takes `&self` instead of `mut &self` because:
37 /// - It prepares the way for async fn,
38 /// since then the future only borrows `&self`, and thus a Service can concurrently handle
39 /// multiple outstanding requests at once.
40 /// - It's clearer that Services can likely be cloned
41 /// - To share state across clones, you generally need `Arc<Mutex<_>>`
42 /// That means you're not really using the `&mut self` and could do with a `&self`.
43 /// The discussion on this is here: <https://github.com/hyperium/hyper/issues/3040>
44 fn call(&self, req: Request) -> Self::Future;
45}
46
47impl<Request, S: Service<Request> + ?Sized> Service<Request> for &'_ S {
48 type Response = S::Response;
49 type Error = S::Error;
50 type Future = S::Future;
51
52 #[inline]
53 fn call(&self, req: Request) -> Self::Future {
54 (**self).call(req)
55 }
56}
57
58impl<Request, S: Service<Request> + ?Sized> Service<Request> for &'_ mut S {
59 type Response = S::Response;
60 type Error = S::Error;
61 type Future = S::Future;
62
63 #[inline]
64 fn call(&self, req: Request) -> Self::Future {
65 (**self).call(req)
66 }
67}
68
69impl<Request, S: Service<Request> + ?Sized> Service<Request> for Box<S> {
70 type Response = S::Response;
71 type Error = S::Error;
72 type Future = S::Future;
73
74 #[inline]
75 fn call(&self, req: Request) -> Self::Future {
76 (**self).call(req)
77 }
78}
79
80impl<Request, S: Service<Request> + ?Sized> Service<Request> for std::rc::Rc<S> {
81 type Response = S::Response;
82 type Error = S::Error;
83 type Future = S::Future;
84
85 #[inline]
86 fn call(&self, req: Request) -> Self::Future {
87 (**self).call(req)
88 }
89}
90
91impl<Request, S: Service<Request> + ?Sized> Service<Request> for std::sync::Arc<S> {
92 type Response = S::Response;
93 type Error = S::Error;
94 type Future = S::Future;
95
96 #[inline]
97 fn call(&self, req: Request) -> Self::Future {
98 (**self).call(req)
99 }
100}
101