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#![deny(rust_2018_idioms, warnings)]
#![allow(clippy::type_complexity)]
use std::future::Future;
use std::rc::Rc;
use std::task::{self, Context, Poll};
mod and_then;
mod and_then_apply_fn;
mod apply;
mod apply_cfg;
pub mod boxed;
mod fn_service;
mod fn_transform;
mod map;
mod map_config;
mod map_err;
mod map_init_err;
mod pipeline;
mod then;
mod transform;
pub use self::apply::{apply_fn, apply_fn_factory};
pub use self::fn_service::{
fn_factory, fn_factory_with_config, fn_mut_service, fn_service,
};
pub use self::fn_transform::fn_transform;
pub use self::map_config::{map_config, map_config_service, unit_config};
pub use self::pipeline::{pipeline, pipeline_factory, Pipeline, PipelineFactory};
pub use self::transform::{apply, Identity, Transform};
#[doc(hidden)]
pub use self::apply_cfg::{apply_cfg, apply_cfg_factory};
/// 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.
///
/// ```rust,ignore
/// 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:
///
/// ```rust,ignore
/// async fn my_service(req: u8) -> Result<u64, MyError>;
/// ```
pub trait Service {
/// Requests handled by the service.
type Request;
/// Responses given by the service.
type Response;
/// Errors produced by the service.
type Error;
/// The future response value.
type Future: Future<Output = Result<Self::Response, 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 poll_ready(&self, ctx: &mut task::Context<'_>) -> Poll<Result<(), Self::Error>>;
#[inline]
#[allow(unused_variables)]
/// Shutdown service.
///
/// Returns `Ready` when the service is properly shutdowned. This method might be called
/// after it returns `Ready`.
fn poll_shutdown(&self, ctx: &mut task::Context<'_>, is_error: bool) -> Poll<()> {
Poll::Ready(())
}
/// 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.
fn call(&self, req: Self::Request) -> Self::Future;
#[inline]
/// 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<F, R>(self, f: F) -> crate::dev::Map<Self, F, R>
where
Self: Sized,
F: FnMut(Self::Response) -> R,
{
crate::dev::Map::new(self, f)
}
#[inline]
/// 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.
fn map_err<F, E>(self, f: F) -> crate::dev::MapErr<Self, F, E>
where
Self: Sized,
F: Fn(Self::Error) -> E,
{
crate::dev::MapErr::new(self, f)
}
}
/// Creates new `Service` values.
///
/// Acts as a service factory. This is useful for cases where new `Service`
/// values must be produced. One case is a TCP server listener. The listener
/// accepts new TCP streams, obtains a new `Service` value using the
/// `ServiceFactory` trait, and uses that new `Service` value to process inbound
/// requests on that new TCP stream.
///
/// `Config` is a service factory configuration type.
pub trait ServiceFactory {
/// Requests handled by the service.
type Request;
/// Responses given by the service
type Response;
/// Errors produced by the service
type Error;
/// Service factory configuration
type Config;
/// The `Service` value created by this factory
type Service: Service<
Request = Self::Request,
Response = Self::Response,
Error = Self::Error,
>;
/// Errors produced while building a service.
type InitError;
/// The future of the `ServiceFactory` instance.
type Future: Future<Output = Result<Self::Service, Self::InitError>>;
/// Create and return a new service value asynchronously.
fn new_service(&self, cfg: Self::Config) -> Self::Future;
#[inline]
/// Map this service's output to a different type, returning a new service
/// of the resulting type.
fn map<F, R>(self, f: F) -> crate::map::MapServiceFactory<Self, F, R>
where
Self: Sized,
F: FnMut(Self::Response) -> R + Clone,
{
crate::map::MapServiceFactory::new(self, f)
}
#[inline]
/// Map this service's error to a different error, returning a new service.
fn map_err<F, E>(self, f: F) -> crate::map_err::MapErrServiceFactory<Self, F, E>
where
Self: Sized,
F: Fn(Self::Error) -> E + Clone,
{
crate::map_err::MapErrServiceFactory::new(self, f)
}
#[inline]
/// Map this factory's init error to a different error, returning a new service.
fn map_init_err<F, E>(self, f: F) -> crate::map_init_err::MapInitErr<Self, F, E>
where
Self: Sized,
F: Fn(Self::InitError) -> E + Clone,
{
crate::map_init_err::MapInitErr::new(self, f)
}
}
impl<S> Service for Box<S>
where
S: Service + ?Sized,
{
type Request = S::Request;
type Response = S::Response;
type Error = S::Error;
type Future = S::Future;
#[inline]
fn poll_ready(&self, cx: &mut Context<'_>) -> Poll<Result<(), S::Error>> {
(**self).poll_ready(cx)
}
#[inline]
fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()> {
(**self).poll_shutdown(cx, is_error)
}
#[inline]
fn call(&self, request: Self::Request) -> S::Future {
(**self).call(request)
}
}
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>> {
(**self).poll_ready(cx)
}
#[inline]
fn poll_shutdown(&self, cx: &mut Context<'_>, is_error: bool) -> Poll<()> {
(**self).poll_shutdown(cx, is_error)
}
fn call(&self, request: Self::Request) -> S::Future {
(**self).call(request)
}
}
impl<S> ServiceFactory for Rc<S>
where
S: ServiceFactory,
{
type Request = S::Request;
type Response = S::Response;
type Error = S::Error;
type Config = S::Config;
type Service = S::Service;
type InitError = S::InitError;
type Future = S::Future;
fn new_service(&self, cfg: S::Config) -> S::Future {
self.as_ref().new_service(cfg)
}
}
/// Trait for types that can be converted to a `Service`
pub trait IntoService<T>
where
T: Service,
{
/// Convert to a `Service`
fn into_service(self) -> T;
}
/// Trait for types that can be converted to a `ServiceFactory`
pub trait IntoServiceFactory<T>
where
T: ServiceFactory,
{
/// Convert `Self` to a `ServiceFactory`
fn into_factory(self) -> T;
}
impl<T> IntoService<T> for T
where
T: Service,
{
fn into_service(self) -> T {
self
}
}
impl<T> IntoServiceFactory<T> for T
where
T: ServiceFactory,
{
fn into_factory(self) -> T {
self
}
}
/// Convert object of type `T` to a service `S`
pub fn into_service<T, S>(tp: T) -> S
where
S: Service,
T: IntoService<S>,
{
tp.into_service()
}
pub mod dev {
pub use crate::apply::{Apply, ApplyServiceFactory};
pub use crate::fn_service::{
FnMutService, FnService, FnServiceConfig, FnServiceFactory, FnServiceNoConfig,
};
pub use crate::fn_transform::FnTransform;
pub use crate::map::{Map, MapServiceFactory};
pub use crate::map_config::{MapConfig, UnitConfig};
pub use crate::map_err::{MapErr, MapErrServiceFactory};
pub use crate::map_init_err::MapInitErr;
pub use crate::transform::ApplyTransform;
}