Trait tower::Layer

source ·

pub trait Layer<S> {
    type Service;

    // Required method
    fn layer(&self, inner: S) -> Self::Service;
}

Expand description

Decorates a Service, transforming either the request or the response.

Often, many of the pieces needed for writing network applications can be reused across multiple services. The Layer trait can be used to write reusable components that can be applied to very different kinds of services; for example, it can be applied to services operating on different protocols, and to both the client and server side of a network transaction.

Log

Take request logging as an example:


pub struct LogLayer {
    target: &'static str,
}

impl<S> Layer<S> for LogLayer {
    type Service = LogService<S>;

    fn layer(&self, service: S) -> Self::Service {
        LogService {
            target: self.target,
            service
        }
    }
}

// This service implements the Log behavior
pub struct LogService<S> {
    target: &'static str,
    service: S,
}

impl<S, Request> Service<Request> for LogService<S>
where
    S: Service<Request>,
    Request: fmt::Debug,
{
    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.service.poll_ready(cx)
    }

    fn call(&mut self, request: Request) -> Self::Future {
        // Insert log statement here or other functionality
        println!("request = {:?}, target = {:?}", request, self.target);
        self.service.call(request)
    }
}

The above log implementation is decoupled from the underlying protocol and is also decoupled from client or server concerns. In other words, the same log middleware could be used in either a client or a server.

Required Associated Types§

source

type Service

The wrapped service

Required Methods§

source

fn layer(&self, inner: S) -> Self::Service

Wrap the given service with the middleware, returning a new service that has been decorated with the middleware.

Trait tower::Layer

Log

Required Associated Types§

type Service

Required Methods§

fn layer(&self, inner: S) -> Self::Service

Implementations on Foreign Types§

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer(&self, service: S) -> <(L1, L2, L3, L4, L5, L6) as Layer<S>>::Service

impl<S, L1> Layer<S> for (L1,)where L1: Layer<S>,

type Service = <L1 as Layer<S>>::Service

fn layer(&self, service: S) -> <(L1,) as Layer<S>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13) as Layer<S>>::Service

impl<S> Layer<S> for ()

type Service = S

fn layer(&self, service: S) -> <() as Layer<S>>::Service

impl<'a, T, S> Layer<S> for &'a Twhere T: Layer<S> + ?Sized,

type Service = <T as Layer<S>>::Service

fn layer(&self, inner: S) -> <&'a T as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<<L7 as Layer<<L8 as Layer<<L9 as Layer<<L10 as Layer<<L11 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11) as Layer<S>>::Service

impl<S, L1, L2> Layer<S> for (L1, L2)where L1: Layer<<L2 as Layer<S>>::Service>, L2: Layer<S>,

type Service = <L1 as Layer<<L2 as Layer<S>>::Service>>::Service

fn layer(&self, service: S) -> <(L1, L2) as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<<L7 as Layer<<L8 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8) as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<<L7 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7) as Layer<S>>::Service

impl<S, L1, L2, L3> Layer<S> for (L1, L2, L3)where L1: Layer<<L2 as Layer<<L3 as Layer<S>>::Service>>::Service>, L2: Layer<<L3 as Layer<S>>::Service>, L3: Layer<S>,

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<S>>::Service>>::Service>>::Service

fn layer(&self, service: S) -> <(L1, L2, L3) as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<<L7 as Layer<<L8 as Layer<<L9 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9) as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer(&self, service: S) -> <(L1, L2, L3, L4, L5) as Layer<S>>::Service

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<<L5 as Layer<<L6 as Layer<<L7 as Layer<<L8 as Layer<<L9 as Layer<<L10 as Layer<S>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10) as Layer<S>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15) as Layer<S>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14, L15, L16) as Layer<S>>::Service

impl<S, L1, L2, L3, L4> Layer<S> for (L1, L2, L3, L4)where L1: Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<S>>::Service>>::Service>>::Service>, L2: Layer<<L3 as Layer<<L4 as Layer<S>>::Service>>::Service>, L3: Layer<<L4 as Layer<S>>::Service>, L4: Layer<S>,

type Service = <L1 as Layer<<L2 as Layer<<L3 as Layer<<L4 as Layer<S>>::Service>>::Service>>::Service>>::Service

fn layer(&self, service: S) -> <(L1, L2, L3, L4) as Layer<S>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12, L13, L14) as Layer<S>>::Service

fn layer( &self, service: S ) -> <(L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11, L12) as Layer<S>>::Service

Implementors§

impl<F, S, Out> Layer<S> for LayerFn<F>where F: Fn(S) -> Out,

type Service = Out

impl<In, T, U, E> Layer<In> for BoxLayer<In, T, U, E>

type Service = BoxService<T, U, E>

impl<P, S> Layer<S> for RetryLayer<P>where P: Clone,

type Service = Retry<P, S>

impl<S> Layer<S> for Identity

type Service = S

impl<S, A, B> Layer<S> for Either<A, B>where A: Layer<S>, B: Layer<S>,

type Service = Either<<A as Layer<S>>::Service, <B as Layer<S>>::Service>

impl<S, F> Layer<S> for AndThenLayer<F>where F: Clone,

type Service = AndThen<S, F>

impl<S, F> Layer<S> for MapErrLayer<F>where F: Clone,

type Service = MapErr<S, F>

impl<S, F> Layer<S> for MapFutureLayer<F>where F: Clone,

type Service = MapFuture<S, F>

impl<S, F> Layer<S> for MapRequestLayer<F>where F: Clone,

type Service = MapRequest<S, F>

impl<S, F> Layer<S> for MapResponseLayer<F>where F: Clone,

type Service = MapResponse<S, F>

impl<S, F> Layer<S> for MapResultLayer<F>where F: Clone,

type Service = MapResult<S, F>

impl<S, F> Layer<S> for ThenLayer<F>where F: Clone,

type Service = Then<S, F>

impl<S, Inner, Outer> Layer<S> for Stack<Inner, Outer>where Inner: Layer<S>, Outer: Layer<<Inner as Layer<S>>::Service>,

type Service = <Outer as Layer<<Inner as Layer<S>>::Service>>::Service

impl<S, L> Layer<S> for ServiceBuilder<L>where L: Layer<S>,

type Service = <L as Layer<S>>::Service