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Steer

tower::steer

Struct Steer 

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pub struct Steer<S, F, Req> { /* private fields */ }
Available on crate feature steer only.
Expand description

Steer manages a list of Services which all handle the same type of request.

An example use case is a sharded service. It accepts new requests, then:

  1. Determines, via the provided Picker, which Service the request corresponds to.
  2. Waits (in Service::poll_ready) for all services to be ready.
  3. Calls the correct Service with the request, and returns a future corresponding to the call.

Note that Steer must wait for all services to be ready since it can’t know ahead of time which Service the next message will arrive for, and is unwilling to buffer items indefinitely. This will cause head-of-line blocking unless paired with a Service that does buffer items indefinitely, and thus always returns Poll::Ready. For example, wrapping each component service with a Buffer with a high enough limit (the maximum number of concurrent requests) will prevent head-of-line blocking in Steer.

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impl<S, F, Req> Steer<S, F, Req>

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pub fn new(services: impl IntoIterator<Item = S>, router: F) -> Self

Make a new Steer with a list of Service’s and a Picker.

Note: the order of the Service’s is significant for Picker::pick’s return value.

Trait Implementations§

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impl<S, F, Req> Clone for Steer<S, F, Req>
where S: Clone, F: Clone,

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fn clone(&self) -> Self

Returns a duplicate of the value. Read more
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fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source. Read more
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impl<S, F, Req> Debug for Steer<S, F, Req>
where S: Debug, F: Debug,

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

Formats the value using the given formatter. Read more
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impl<S, Req, F> Service<Req> for Steer<S, F, Req>
where S: Service<Req>, F: Picker<S, Req>,

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type Response = <S as Service<Req>>::Response

Responses given by the service.
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type Error = <S as Service<Req>>::Error

Errors produced by the service.
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type Future = <S as Service<Req>>::Future

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

Returns Poll::Ready(Ok(())) when the service is able to process requests. Read more
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fn call(&mut self, req: Req) -> Self::Future

Process the request and return the response asynchronously. Read more

Auto Trait Implementations§

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impl<S, F, Req> Freeze for Steer<S, F, Req>
where F: Freeze,

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impl<S, F, Req> RefUnwindSafe for Steer<S, F, Req>
where F: RefUnwindSafe, Req: RefUnwindSafe, S: RefUnwindSafe,

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impl<S, F, Req> Send for Steer<S, F, Req>
where F: Send, Req: Send, S: Send,

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impl<S, F, Req> Sync for Steer<S, F, Req>
where F: Sync, Req: Sync, S: Sync,

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impl<S, F, Req> Unpin for Steer<S, F, Req>
where F: Unpin, Req: Unpin, S: Unpin,

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impl<S, F, Req> UnwindSafe for Steer<S, F, Req>
where F: UnwindSafe, Req: UnwindSafe, S: UnwindSafe,

Blanket Implementations§

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impl<T> Any for T
where T: 'static + ?Sized,

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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impl<T> CloneToUninit for T
where T: Clone,

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unsafe fn clone_to_uninit(&self, dest: *mut u8)

🔬This is a nightly-only experimental API. (clone_to_uninit)
Performs copy-assignment from self to dest. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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impl<T> Instrument for T

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fn instrument(self, span: Span) -> Instrumented<Self>

Instruments this type with the provided Span, returning an Instrumented wrapper. Read more
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fn in_current_span(self) -> Instrumented<Self>

Instruments this type with the current Span, returning an Instrumented wrapper. Read more
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impl<T, U> Into<U> for T
where U: From<T>,

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<M, S, Target, Request> MakeService<Target, Request> for M
where M: Service<Target, Response = S>, S: Service<Request>,

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type Response = <S as Service<Request>>::Response

Available on crate feature make only.
Responses given by the service
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type Error = <S as Service<Request>>::Error

Available on crate feature make only.
Errors produced by the service
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type Service = S

Available on crate feature make only.
The Service value created by this factory
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type MakeError = <M as Service<Target>>::Error

Available on crate feature make only.
Errors produced while building a service.
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type Future = <M as Service<Target>>::Future

Available on crate feature make only.
The future of the Service instance.
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fn poll_ready( &mut self, cx: &mut Context<'_>, ) -> Poll<Result<(), <M as MakeService<Target, Request>>::MakeError>>

Available on crate feature make only.
Returns Poll::Ready when the factory is able to create more services. Read more
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fn make_service( &mut self, target: Target, ) -> <M as MakeService<Target, Request>>::Future

Available on crate feature make only.
Create and return a new service value asynchronously.
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fn into_service(self) -> IntoService<Self, Request>
where Self: Sized,

Available on crate feature make only.
Consume this MakeService and convert it into a Service. Read more
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fn as_service(&mut self) -> AsService<'_, Self, Request>
where Self: Sized,

Available on crate feature make only.
Convert this MakeService into a Service without consuming the original MakeService. Read more
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impl<T, Request> ServiceExt<Request> for T
where T: Service<Request> + ?Sized,

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fn ready(&mut self) -> Ready<'_, Self, Request> ⓘ
where Self: Sized,

Available on crate feature util only.
Yields a mutable reference to the service when it is ready to accept a request.
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fn ready_oneshot(self) -> ReadyOneshot<Self, Request> ⓘ
where Self: Sized,

Available on crate feature util only.
Yields the service when it is ready to accept a request.
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fn oneshot(self, req: Request) -> Oneshot<Self, Request> ⓘ
where Self: Sized,

Available on crate feature util only.
Consume this Service, calling it with the provided request once it is ready.
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fn call_all<S>(self, reqs: S) -> CallAll<Self, S>
where Self: Sized, S: Stream<Item = Request>,

Available on crate feature util only.
Process all requests from the given Stream, and produce a Stream of their responses. Read more
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fn and_then<F>(self, f: F) -> AndThen<Self, F>
where Self: Sized, F: Clone,

Available on crate feature util only.
Executes a new future after this service’s future resolves. This does not alter the behaviour of the poll_ready method. Read more
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fn map_response<F, Response>(self, f: F) -> MapResponse<Self, F>
where Self: Sized, F: FnOnce(Self::Response) -> Response + Clone,

Available on crate feature util only.
Maps this service’s response value to a different value. This does not alter the behaviour of the poll_ready method. Read more
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fn map_err<F, Error>(self, f: F) -> MapErr<Self, F>
where Self: Sized, F: FnOnce(Self::Error) -> Error + Clone,

Available on crate feature util only.
Maps this service’s error value to a different value. This does not alter the behaviour of the poll_ready method. Read more
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fn map_result<F, Response, Error>(self, f: F) -> MapResult<Self, F>
where Self: Sized, Error: From<Self::Error>, F: FnOnce(Result<Self::Response, Self::Error>) -> Result<Response, Error> + Clone,

Available on crate feature util only.
Maps this service’s result type (Result<Self::Response, Self::Error>) to a different value, regardless of whether the future succeeds or fails. Read more
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fn map_request<F, NewRequest>(self, f: F) -> MapRequest<Self, F>
where Self: Sized, F: FnMut(NewRequest) -> Request,

Available on crate feature util only.
Composes a function in front of the service. Read more
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fn filter<F, NewRequest>(self, filter: F) -> Filter<Self, F>
where Self: Sized, F: Predicate<NewRequest>,

Available on crate features util and filter only.
Composes this service with a Filter that conditionally accepts or rejects requests based on a predicate. Read more
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fn filter_async<F, NewRequest>(self, filter: F) -> AsyncFilter<Self, F>
where Self: Sized, F: AsyncPredicate<NewRequest>,

Available on crate features util and filter only.
Composes this service with an AsyncFilter that conditionally accepts or rejects requests based on an [async predicate]. Read more
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fn then<F, Response, Error, Fut>(self, f: F) -> Then<Self, F>
where Self: Sized, Error: From<Self::Error>, F: FnOnce(Result<Self::Response, Self::Error>) -> Fut + Clone, Fut: Future<Output = Result<Response, Error>>,

Available on crate feature util only.
Composes an asynchronous function after this service. Read more
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fn map_future<F, Fut, Response, Error>(self, f: F) -> MapFuture<Self, F>
where Self: Sized, F: FnMut(Self::Future) -> Fut, Error: From<Self::Error>, Fut: Future<Output = Result<Response, Error>>,

Available on crate feature util only.
Composes a function that transforms futures produced by the service. Read more
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fn boxed(self) -> BoxService<Request, Self::Response, Self::Error>
where Self: Sized + Send + 'static, Self::Future: Send + 'static,

Available on crate feature util only.
Convert the service into a Service + Send trait object. Read more
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fn boxed_clone(self) -> BoxCloneService<Request, Self::Response, Self::Error>
where Self: Clone + Sized + Send + 'static, Self::Future: Send + 'static,

Available on crate feature util only.
Convert the service into a Service + Clone + Send trait object. Read more
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impl<T> ToOwned for T
where T: Clone,

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type Owned = T

The resulting type after obtaining ownership.
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fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more
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fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more
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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.
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impl<T> WithSubscriber for T

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fn with_subscriber<S>(self, subscriber: S) -> WithDispatch<Self>
where S: Into<Dispatch>,

Attaches the provided Subscriber to this type, returning a WithDispatch wrapper. Read more
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fn with_current_subscriber(self) -> WithDispatch<Self>

Attaches the current default Subscriber to this type, returning a WithDispatch wrapper. Read more