How to specify static service methods? #2669

ghost · 2021-10-17T09:00:24Z

ghost
Oct 17, 2021

I added lifetime to custom service to trait to indicate static lifetime but still fails. Why?
I know I call self.kool() before the async but can we not call it inside async with explicit static lifetime.

use std::env::var;
use std::marker::PhantomData;
use std::pin::Pin;
use std::task::{Context, Poll};
use futures::Future;
use hyper::service::Service;
use hyper::{Body, Request, Response, StatusCode};
use mongodb::options::ClientOptions;

pub struct MakeSvc<'a> {
    pub(crate) _lifetime: PhantomData<&'a ()>
}

#[derive(Clone)]
pub struct Svc<'a> {
    pub m: mongodb::Client,
    pub(crate) _lifetime: PhantomData<&'a ()>
}

impl <'a> Svc<'a> {
    pub async fn kool(&'a self)->i32{
        99
    }
}

impl<'a,T> Service<T> for MakeSvc<'a>{
    type Response = Svc<'a>;
    type Error = hyper::Error;
    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>> + Send>>;
    fn poll_ready(&mut self, _: &mut Context) -> Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }
    fn call(&mut self, _: T) -> Self::Future {
        let fut = async move {
            let mongo_url = var("MONGO").unwrap_or("mongodb://localhost:27017".to_string());
            let client_options = ClientOptions::parse(mongo_url).await.unwrap();
            let m = mongodb::Client::with_options(client_options).unwrap();
            Ok(Svc { m,  _lifetime: Default::default() })
        };
        Box::pin(fut)
    }
}

impl<'a> Service<Request<Body>> for Svc<'a> {
    type Response = Response<Body>;
    type Error = hyper::Error;
    type Future = Pin<Box<dyn Future<Output = Result<Self::Response, Self::Error>>  +'a + Send>>;
    fn poll_ready(&mut self, _: &mut Context) -> Poll<Result<(), Self::Error>> {
        Poll::Ready(Ok(()))
    }
    fn call(&mut self, req: Request<Body>) -> Self::Future {
        let res = async move {
            match (req.method(), req.uri().path()) {
                _ => {
                    self.kool();
                    Ok(Response::builder()
                        .status(StatusCode::NOT_FOUND)
                        .body("sorry".into())
                        .unwrap())
                }
            }
        };
        Box::pin(res)
    }
}

[dependencies]
tokio = { version = "1.8.0", features = ["full"] }
hyper = {version="0.14.13",features=["full"]}
tower = {version="0.4.8", features=["full"]}
mongodb = {version="2.0.1"}
futures = "0.3.15"

seanmonstar · 2021-10-18T23:06:22Z

seanmonstar
Oct 18, 2021
Maintainer

You currently can't do exactly what you're asking. The future returned from Service::call must be static, but trying to access &mut self inside an async { .. } block means the future would need a reference to the service. You could try these things:

Call the method before the block, and move the value into the future.
Make your service cheap to clone, move a clone into the future, and call it then.

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How to specify static service methods? #2669

ghost Oct 17, 2021

Replies: 1 comment

seanmonstar Oct 18, 2021 Maintainer

ghost
Oct 17, 2021

seanmonstar
Oct 18, 2021
Maintainer