Trait ntex_service::Service

pub trait Service {
    type Request;
    type Response;
    type Error;
    type Future: Future<Output = Result<Self::Response, Self::Error>>;
    fn poll_ready(&self, ctx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>;
    fn call(&self, req: Self::Request) -> Self::Future;

    fn poll_shutdown(&self, ctx: &mut Context<'_>, is_error: bool) -> Poll<()> { ... }
    fn map<F, R>(self, f: F) -> Map<Self, F, R>
    where
        Self: Sized,
        F: FnMut(Self::Response) -> R,
    { ... }
    fn map_err<F, E>(self, f: F) -> MapErr<Self, F, E>
    where
        Self: Sized,
        F: Fn(Self::Error) -> E,
    { ... }
}

An asynchronous function from Request to a Response.

Service represents a service that represanting interation, taking requests and giving back replies. You can think about service as a function with one argument and result as a return type. In general form it looks like async fn(Req) -> Result<Res, Err>. Service trait just generalizing form of this function. Each parameter described as an assotiated type.

Services provides a symmetric and uniform API, same abstractions represents clients and servers. Services describe only transforamtion operation which encorouge to simplify api surface and phrases value transformation. That leads to simplier design of each service. That also allows better testability and better composition.

Services could be represented in several different forms. In general, Service is a type that implements Service trait.

struct MyService;

impl Service for MyService {
     type Request = u8;
     type Response = u64;
     type Error = MyError;
     type Future = Pin<Box<Future<Output=Result<Self::Response, Self::Error>>>;

     fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> { ... }

     fn call(&self, req: Self::Request) -> Self::Future { ... }
}

Service can have mutable state that influence computation. This service could be rewritten as a simple function:

async fn my_service(req: u8) -> Result<u64, MyError>;

Associated Types

type Request

Requests handled by the service.

type Response

Responses given by the service.

type Error

Errors produced by the service.

type Future: Future<Output = Result<Self::Response, Self::Error>>

The future response value.

Required methods

fn poll_ready(&self, ctx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

Returns Ready when the service is able to process requests.

If the service is at capacity, then Pending is returned and the task is notified when the service becomes ready again. This function is expected to be called while on a task.

This is a best effort implementation. False positives are permitted. It is permitted for the service to return Ready from a poll_ready call and the next invocation of call results in an error.

There are several notes to consider:

1. .poll_ready() might be called on different task from actual service call.

2. In case of chained services, .poll_ready() get called for all services at once.

fn call(&self, req: Self::Request) -> Self::Future

Process the request and return the response asynchronously.

This function is expected to be callable off task. As such, implementations should take care to not call poll_ready. If the service is at capacity and the request is unable to be handled, the returned Future should resolve to an error.

Calling call without calling poll_ready is permitted. The implementation must be resilient to this fact.

Provided methods

fn poll_shutdown(&self, ctx: &mut Context<'_>, is_error: bool) -> Poll<()>

Shutdown service.

Returns Ready when the service is properly shutdowned. This method might be called after it returns Ready.

fn map<F, R>(self, f: F) -> Map<Self, F, R> where
    Self: Sized,
    F: FnMut(Self::Response) -> R, 

Map this service’s output to a different type, returning a new service of the resulting type.

This function is similar to the Option::map or Iterator::map where it will change the type of the underlying service.

Note that this function consumes the receiving service and returns a wrapped version of it, similar to the existing map methods in the standard library.

fn map_err<F, E>(self, f: F) -> MapErr<Self, F, E> where
    Self: Sized,
    F: Fn(Self::Error) -> E, 

Map this service’s error to a different error, returning a new service.

This function is similar to the Result::map_err where it will change the error type of the underlying service. This is useful for example to ensure that services have the same error type.

Note that this function consumes the receiving service and returns a wrapped version of it.

Implementations on Foreign Types

impl<S: ?Sized> Service for Box<S> where
    S: Service, 

type Request = S::Request

type Response = S::Response

type Error = S::Error

type Future = S::Future

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), S::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, request: Self::Request) -> S::Future

impl<S> Service for Rc<S> where
    S: Service, 

type Request = S::Request

type Response = S::Response

type Error = S::Error

type Future = S::Future

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, request: Self::Request) -> S::Future

Implementors

impl<A, F, E> Service for MapErr<A, F, E> where
    A: Service,
    F: Fn(A::Error) -> E + Clone, 

type Request = A::Request

type Response = A::Response

type Error = E

type Future = MapErrFuture<A, F, E>

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, req: A::Request) -> Self::Future

impl<A, F, Response> Service for Map<A, F, Response> where
    A: Service,
    F: FnMut(A::Response) -> Response + Clone, 

type Request = A::Request

type Response = Response

type Error = A::Error

type Future = MapFuture<A, F, Response>

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, req: A::Request) -> Self::Future

impl<F, Fut, Req, Res, Err> Service for FnMutService<F, Fut, Req, Res, Err> where
    F: FnMut(Req) -> Fut,
    Fut: Future<Output = Result<Res, Err>>, 

type Request = Req

type Response = Res

type Error = Err

type Future = Fut

fn poll_ready(&self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn call(&self, req: Req) -> Self::Future

impl<F, Fut, Req, Res, Err, FShut> Service for FnService<F, Fut, Req, Res, Err, FShut> where
    F: Fn(Req) -> Fut,
    FShut: FnOnce(),
    Fut: Future<Output = Result<Res, Err>>, 

type Request = Req

type Response = Res

type Error = Err

type Future = Fut

fn poll_ready(&self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, _: &mut Context<'_>, _: bool) -> Poll<()>

fn call(&self, req: Req) -> Self::Future

impl<F, Fut, Req, Res, Err, FShut> Service for FnServiceFactory<F, Fut, Req, Res, Err, (), FShut> where
    F: Fn(Req) -> Fut,
    FShut: FnOnce(),
    Fut: Future<Output = Result<Res, Err>>, 

type Request = Req

type Response = Res

type Error = Err

type Future = Fut

fn poll_ready(&self, _: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, _: &mut Context<'_>, _: bool) -> Poll<()>

fn call(&self, req: Self::Request) -> Self::Future

impl<T, F, R, In, Out, Err> Service for Apply<T, F, R, In, Out, Err> where
    T: Service<Error = Err>,
    F: Fn(In, &T) -> R,
    R: Future<Output = Result<Out, Err>>, 

type Request = In

type Response = Out

type Error = Err

type Future = R

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, req: In) -> Self::Future

impl<T: Service> Service for Pipeline<T>

type Request = T::Request

type Response = T::Response

type Error = T::Error

type Future = T::Future

fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), T::Error>>

fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()>

fn call(&self, req: T::Request) -> Self::Future