Trait tower::Layer [−][src]
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.
Associated Types
Required methods
Implementations on Foreign Types
Implementors
type Service = BoxService<T, U, E>
impl<P, S> Layer<S> for RetryLayer<P> where
P: Clone,
This is supported on crate feature retry
only.
impl<P, S> Layer<S> for RetryLayer<P> where
P: Clone,
This is supported on crate feature
retry
only.type Service = ConcurrencyLimit<S>
type Service = ConcurrencyLimit<S>
type Service = MakeSpawnReady<S>
impl<S, F> Layer<S> for AndThenLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for AndThenLayer<F> where
F: Clone,
This is supported on crate feature
util
only.impl<S, F> Layer<S> for MapErrLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for MapErrLayer<F> where
F: Clone,
This is supported on crate feature
util
only.impl<S, F> Layer<S> for MapFutureLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for MapFutureLayer<F> where
F: Clone,
This is supported on crate feature
util
only.impl<S, F> Layer<S> for MapRequestLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for MapRequestLayer<F> where
F: Clone,
This is supported on crate feature
util
only.type Service = MapRequest<S, F>
impl<S, F> Layer<S> for MapResponseLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for MapResponseLayer<F> where
F: Clone,
This is supported on crate feature
util
only.type Service = MapResponse<S, F>
impl<S, F> Layer<S> for MapResultLayer<F> where
F: Clone,
This is supported on crate feature util
only.
impl<S, F> Layer<S> for MapResultLayer<F> where
F: Clone,
This is supported on crate feature
util
only.