☀️ State

To recap, a Service::serve method has the following signature:

fn serve(
    &self,
    req: Request,
) -> impl Future<Output = Result<Self::Response, Self::Error>> + Send + '_;

• &self allows services to access shared Send + Sync + 'static state internal and specific to that Service;
• Request is the input used to produce a Result. Request also contains Extensions which can be used to store dynamic state

Types of state

rama supports two kinds of states:

1. static state: this state can be a part of the service struct or captured by a closure
2. dynamic state: these can be injected as Extensionss using methods such as Extensions::insert or request.extensions_mut().insert

Any state that is optional, and especially optional state injected by middleware, can be inserted using extensions. It is however important to try as much as possible to then also consume this state in an approach that deals gracefully with its absence. Good examples of this are header-related inputs. Headers might be set or not, and so absence of Extensionss that might be created as a result of these might reasonably not exist. It might of course still mean the app returns an error response when it is absent, but it should not unwrap/panic.

Extensions

Extensions is what this chapter is about, and its documemtation can be consumed at https://ramaproxy.org/docs/rama/extensions/struct.Extensions.html.

• access Extensions that can be used to dynamically get and set extra (optional) data, to be passed for usage by inner service(s).