Just Middleware. #21
Just Middleware. #21
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A middleware is a function from Service to Service. Two combinators are provided: * Service::wrap (equivalent to function application) * Middleware::chain (equivalent to function composition)
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This branch doesn't have any of the streaming services stuff, just the middleware definition. |
| @@ -155,6 +99,14 @@ pub trait Service { | |||
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| /// Process the request and return the response asynchronously. | |||
| fn call(&self, req: Self::Request) -> Self::Future; | |||
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| /// Wrap this Service in a Middleware component. | |||
| fn wrap<M>(self, middleware: M) -> M::WrappedService where | |||
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Technically speaking the middleware wraps the service, but the service doesn't wrap the middleware, so I guess that the method should be named wrapped_by(). This is slightly confusing, because the middleware also has a method named wrap().
I don't have a perfect alternative name, but it might here are some ideas: apply() , filter() , using() , with() wrapped()
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I'm OK w/ the name wrap here.
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I think wrap works in both directions, in the sense of wrap in {middleware} and wrap around {service}. But I'm also fine with whatever name.
| /// | ||
| /// This allows you to build middleware chains before knowing | ||
| /// exactly which service that chain applies to. | ||
| fn chain<M>(self, middleware: M) -> MiddlewareChain<S, Self, M> where |
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Alternative you could use a builder to create MiddlewareChain. That would allow MiddlewareChain to live in a separate crate.
let middleware = MiddlewareChainBuilder::new(middleware1)
.chain(middleware2)
.chain(middleware3);
let service = Myservice::new().wrap(middleware);I wonder how often MiddlewareChain will actually be used. It might be easier to write a function that applies the necessary middleware to the service or to wrap each service independently. If MiddlewareChain to lives in a separate crate, then it is easier to experiment.
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I kind of like the idea of keeping the "chain" concept off the Middleware trait... though I don't know if it should be in a separate crate or not.
Also, I think finagle calls this concept a "stack", but I am not super adept at reading scala...
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So I have use for chain in the framework I'm writing. HTTP services are constructed through a DSL, and then users can in that DSL declare a middleware to be applied to them. It can be easier for them if they can chain middleware together to produce a the middleware they're going to be applying. They never have access to the Service type directly so they can't just use wrap.
| pub trait Middleware<S: Service> { | ||
| /// The service produced by wrapping this middleware around another | ||
| /// service. | ||
| type WrappedService: Service; |
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If we are going to bike shed, I think it could be nice to come up w/ a shorter name for this associated type... I would say Upstream, but up and down seem to get everyone confused...
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We could just call it Wrapped?
| /// | ||
| /// This allows you to build middleware chains before knowing | ||
| /// exactly which service that chain applies to. | ||
| fn chain<M>(self, middleware: M) -> MiddlewareChain<S, Self, M> where |
There was a problem hiding this comment.
I kind of like the idea of keeping the "chain" concept off the Middleware trait... though I don't know if it should be in a separate crate or not.
Also, I think finagle calls this concept a "stack", but I am not super adept at reading scala...
| @@ -155,6 +99,14 @@ pub trait Service { | |||
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| /// Process the request and return the response asynchronously. | |||
| fn call(&self, req: Self::Request) -> Self::Future; | |||
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| /// Wrap this Service in a Middleware component. | |||
| fn wrap<M>(self, middleware: M) -> M::WrappedService where | |||
There was a problem hiding this comment.
I'm OK w/ the name wrap here.
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Hey guys, what's the state with that issue? |
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Dev is being moved to Tower. |
A middleware is a function from Service to Service.
Two combinators are provided: