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Allow third-party devs to write custom plugins for service builders (#…
…1736) * Allow custom layers to every operation Third-party developers can add custom functions to a service builder, through a `BuilderModifier`. These functionalities are applied to every operation of that service. An example of a builder modifier can be found in rust-runtime/aws-smithy-http-server/examples/pokemon-service/lib.rs Signed-off-by: Harry Barber <[email protected]> Signed-off-by: Daniele Ahmed <[email protected]> Co-authored-by: Harry Barber <[email protected]>
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rust-runtime/aws-smithy-http-server/examples/pokemon-service/src/plugin.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| /* | ||
| * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
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| use aws_smithy_http_server::plugin::Plugin; | ||
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| /// A [`Service`](tower::Service) that adds a print log. | ||
| #[derive(Clone, Debug)] | ||
| pub struct PrintService<S> { | ||
| inner: S, | ||
| name: &'static str, | ||
| } | ||
|
|
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| impl<R, S> tower::Service<R> for PrintService<S> | ||
| where | ||
| S: tower::Service<R>, | ||
| { | ||
| type Response = S::Response; | ||
| type Error = S::Error; | ||
| type Future = S::Future; | ||
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| fn poll_ready(&mut self, cx: &mut std::task::Context<'_>) -> std::task::Poll<Result<(), Self::Error>> { | ||
| self.inner.poll_ready(cx) | ||
| } | ||
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| fn call(&mut self, req: R) -> Self::Future { | ||
| println!("Hi {}", self.name); | ||
| self.inner.call(req) | ||
| } | ||
| } | ||
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| /// A [`Layer`](tower::Layer) which constructs the [`PrintService`]. | ||
| #[derive(Debug)] | ||
| pub struct PrintLayer { | ||
| name: &'static str, | ||
| } | ||
| impl<S> tower::Layer<S> for PrintLayer { | ||
| type Service = PrintService<S>; | ||
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| fn layer(&self, service: S) -> Self::Service { | ||
| PrintService { | ||
| inner: service, | ||
| name: self.name, | ||
| } | ||
| } | ||
| } | ||
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| /// A [`Plugin`]() for a service builder to add a [`PrintLayer`] over operations. | ||
| #[derive(Debug)] | ||
| pub struct PrintPlugin; | ||
| impl<P, Op, S, L> Plugin<P, Op, S, L> for PrintPlugin | ||
| where | ||
| Op: aws_smithy_http_server::operation::OperationShape, | ||
| { | ||
| type Service = S; | ||
| type Layer = tower::layer::util::Stack<L, PrintLayer>; | ||
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| fn map( | ||
| &self, | ||
| input: aws_smithy_http_server::operation::Operation<S, L>, | ||
| ) -> aws_smithy_http_server::operation::Operation<Self::Service, Self::Layer> { | ||
| input.layer(PrintLayer { name: Op::NAME }) | ||
| } | ||
| } | ||
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| /// An extension to service builders to add the `print()` function. | ||
| pub trait PrintExt: aws_smithy_http_server::plugin::Pluggable<PrintPlugin> { | ||
| /// Causes all operations to print the operation name when called. | ||
| /// | ||
| /// This works by applying the [`PrintPlugin`]. | ||
| fn print(self) -> Self::Output | ||
| where | ||
| Self: Sized, | ||
| { | ||
| self.apply(PrintPlugin) | ||
| } | ||
| } | ||
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| impl<Builder> PrintExt for Builder where Builder: aws_smithy_http_server::plugin::Pluggable<PrintPlugin> {} |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,79 @@ | ||
| /* | ||
| * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved. | ||
| * SPDX-License-Identifier: Apache-2.0 | ||
| */ | ||
|
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| use crate::operation::Operation; | ||
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| /// Provides a standard interface for applying [`Plugin`]s to a service builder. This is implemented automatically for all builders. | ||
| /// As [`Plugin`]s modify the way in which [`Operation`]s are [`upgraded`](crate::operation::Upgradable) we can use [`Pluggable`] as a foundation | ||
| /// to write extension traits for all builders. | ||
| /// | ||
| /// # Example | ||
| /// | ||
| /// ``` | ||
| /// # struct PrintPlugin; | ||
| /// # use aws_smithy_http_server::plugin::Pluggable; | ||
| /// trait PrintExt: Pluggable<PrintPlugin> { | ||
| /// fn print(self) -> Self::Output where Self: Sized { | ||
| /// self.apply(PrintPlugin) | ||
| /// } | ||
| /// } | ||
| /// impl<Builder> PrintExt for Builder where Builder: Pluggable<PrintPlugin> {} | ||
| /// ``` | ||
| pub trait Pluggable<NewPlugin> { | ||
| type Output; | ||
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| /// A service builder applies this `plugin`. | ||
| fn apply(self, plugin: NewPlugin) -> Self::Output; | ||
| } | ||
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| /// Maps one [`Operation`] to another, | ||
| /// parameterised by the protocol `P` and operation shape `Op` to allow for plugin behaviour to be specialised accordingly. | ||
| /// | ||
| /// This is passed to [`Pluggable::apply`] to modify the behaviour of the builder. | ||
| pub trait Plugin<P, Op, S, L> { | ||
| type Service; | ||
| type Layer; | ||
|
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| /// Map an [`Operation`] to another. | ||
| fn map(&self, input: Operation<S, L>) -> Operation<Self::Service, Self::Layer>; | ||
| } | ||
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| /// An [`Plugin`] that maps an `input` [`Operation`] to itself. | ||
| pub struct IdentityPlugin; | ||
| impl<P, Op, S, L> Plugin<P, Op, S, L> for IdentityPlugin { | ||
| type Service = S; | ||
| type Layer = L; | ||
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| fn map(&self, input: Operation<S, L>) -> Operation<S, L> { | ||
| input | ||
| } | ||
| } | ||
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| /// A wrapper struct which composes an `Inner` and an `Outer` [`Plugin`]. | ||
| pub struct PluginStack<Inner, Outer> { | ||
| inner: Inner, | ||
| outer: Outer, | ||
| } | ||
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| impl<Inner, Outer> PluginStack<Inner, Outer> { | ||
| /// Creates a new [`PluginStack`]. | ||
| pub fn new(inner: Inner, outer: Outer) -> Self { | ||
| PluginStack { inner, outer } | ||
| } | ||
| } | ||
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| impl<P, Op, S, L, Inner, Outer> Plugin<P, Op, S, L> for PluginStack<Inner, Outer> | ||
| where | ||
| Inner: Plugin<P, Op, S, L>, | ||
| Outer: Plugin<P, Op, Inner::Service, Inner::Layer>, | ||
| { | ||
| type Service = Outer::Service; | ||
| type Layer = Outer::Layer; | ||
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| fn map(&self, input: Operation<S, L>) -> Operation<Self::Service, Self::Layer> { | ||
| let inner = self.inner.map(input); | ||
| self.outer.map(inner) | ||
| } | ||
| } |