actix-web(3) logging middleware with slog (2.7)

request_logging.rs

use actix_service::{Service, Transform};
use actix_web::{dev::ServiceRequest, dev::ServiceResponse, Error};
use futures::future::{ok, Ready};
use futures::{Future};
use slog::info;
use futures::task::Poll;
use std::task::Context;
use std::pin::Pin;


// There are two step in middleware processing.
// 1. Middleware initialization, middleware factory get called with
//    next service in chain as parameter.
// 2. Middleware's call method get called with normal request.
pub struct Logging {
    logger: slog::Logger,
}

impl Logging {
    pub fn new(logger: slog::Logger) -> Logging {
        Logging { logger }
    }
}

// Middleware factory is `Transform` trait from actix-service crate
// `S` - type of the next service
// `B` - type of response's body
impl<S, B> Transform<S> for Logging
    where
        S: Service<Request=ServiceRequest, Response=ServiceResponse<B>, Error=Error>,
        S::Future: 'static,
        B: 'static,
{
    type Request = ServiceRequest;
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Transform = LoggingMiddleware<S>;
    type InitError = ();
    type Future = Ready<Result<Self::Transform, Self::InitError>>;

    fn new_transform(&self, service: S) -> Self::Future {
        ok(LoggingMiddleware {
            service,
            logger: self.logger.clone(),
        })
    }
}

pub struct LoggingMiddleware<S> {
    service: S,
    logger: slog::Logger,
}

impl<S, B> Service for LoggingMiddleware<S>
    where
        S: Service<Request=ServiceRequest, Response=ServiceResponse<B>, Error=Error>,
        S::Future: 'static,
        B: 'static,
{
    type Request = ServiceRequest;
    type Response = ServiceResponse<B>;
    type Error = Error;
    type Future = Pin<Box<dyn Future<Output=Result<Self::Response, Self::Error>>>>;

    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
        self.service.poll_ready(cx)
    }

    fn call(&mut self, req: ServiceRequest) -> Self::Future {
        let fut = self.service.call(req);
        
        let logger = self.logger.clone();
        
        Box::pin(async move {
            let start_time = chrono::Utc::now();

            let res = fut.await?;
            let req = res.request();

            let end_time = chrono::Utc::now();
            let duration = end_time - start_time;

            info!(logger, "handled request";
                "responseTime" => duration.num_milliseconds(),
                "url" => %req.uri(),
                "route" => req.path(),
                "method" => %req.method(),
                "statusCode" => res.status().as_u16()
            );

            Ok(res)
        })
    }
}

// App::new().wrap(Logging::new(root_logger.clone()))