Struct tower::util::BoxCloneServiceLayer

pub struct BoxCloneServiceLayer<In, T, U, E> { /* private fields */ }

A Clone + Send boxed Layer.

BoxCloneServiceLayer turns a layer into a trait object, allowing both the Layer itself and the output Service to be dynamic, while having consistent types.

This Layer produces BoxCloneService instances erasing the type of the Service produced by the wrapped Layer.

This is similar to BoxLayer except the layer and resulting service implements Clone.

Example

BoxCloneServiceLayer can, for example, be useful to create layers dynamically that otherwise wouldn’t have the same types, when the underlying service must be clone (for example, when building a MakeService) In this example, we include a Timeout layer only if an environment variable is set. We can use BoxCloneService to return a consistent type regardless of runtime configuration:

use std::time::Duration;
use tower::{Service, ServiceBuilder, BoxError};
use tower::util::{BoxCloneServiceLayer, BoxCloneService};


fn common_layer<S, T>() -> BoxCloneServiceLayer<S, T, S::Response, BoxError>
where
    S: Service<T> + Clone + Send + 'static,
    S::Future: Send + 'static,
    S::Error: Into<BoxError> + 'static,
{
    let builder = ServiceBuilder::new()
        .concurrency_limit(100);

    if std::env::var("SET_TIMEOUT").is_ok() {
        let layer = builder
            .timeout(Duration::from_secs(30))
            .into_inner();

        BoxCloneServiceLayer::new(layer)
    } else {
        let layer = builder
            .map_err(Into::into)
            .into_inner();

        BoxCloneServiceLayer::new(layer)
    }
}

// We can clone the layer (this is true of BoxLayer as well)
let boxed_clone_layer = common_layer();

let cloned_layer = boxed_clone_layer.clone();

// Using the `BoxCloneServiceLayer` we can create a `BoxCloneService`
let service: BoxCloneService<Request, Response, BoxError> = ServiceBuilder::new().layer(boxed_clone_layer)
     .service_fn(|req: Request| async {
        Ok::<_, BoxError>(Response::new())
    });


// And we can still clone the service
let cloned_service = service.clone();

Implementations

impl<In, T, U, E> BoxCloneServiceLayer<In, T, U, E>

pub fn new<L>(inner_layer: L) -> Self

where L: Layer<In> + Send + Sync + 'static, L::Service: Service<T, Response = U, Error = E> + Send + Clone + 'static, <L::Service as Service<T>>::Future: Send + 'static,

Create a new BoxCloneServiceLayer.

Trait Implementations

impl<In, T, U, E> Clone for BoxCloneServiceLayer<In, T, U, E>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl<In, T, U, E> Debug for BoxCloneServiceLayer<In, T, U, E>

fn fmt(&self, fmt: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

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

type Service = BoxCloneService<T, U, E>

The wrapped service

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

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