Cargo.toml

[package]
name = "warp-tracing"
version = "0.1.0"
edition = "2021"

# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html

[dependencies]
futures-util = "0.3.18"
tokio = { version = "1.14.0", features = ["full"] }
tracing = "0.1.29"
tracing-subscriber = { version = "0.3.3", features = ["env-filter"] }
warp = "0.3.2"

main.rs

#![deny(warnings)]
use std::convert::Infallible;

use futures_util::StreamExt;
use tracing_subscriber::fmt::format::FmtSpan;
use warp::{
    hyper::{Body, Response},
    Filter, Reply,
};

#[tokio::main]
async fn main() {
    let filter = std::env::var("RUST_LOG").unwrap_or_else(|_| "tracing=info,warp=debug".to_owned());

    tracing_subscriber::fmt()
        .with_env_filter(filter)
        .with_span_events(FmtSpan::CLOSE)
        .init();

    let hello = warp::path("hello")
        .and(warp::get())
        .map(|| {
            tracing::info!("saying hello...");
            "Hello, World!"
        })
        .with(warp::trace::named("hello"));

    let goodbye = warp::path("goodbye")
        .and(warp::get())
        .and_then(|| async {
            println!("in goodbye");
            let chunks: Vec<Result<_, std::io::Error>> = vec![Ok("hello"), Ok(" "), Ok("world")];

            let stream = futures_util::stream::iter(chunks).map(|chunk| {
                println!("sending chunk");
                chunk
            });

            let body = Body::wrap_stream(stream);
            println!("will return body");
            Ok::<Box<dyn Reply>, Infallible>(Box::new(Response::new(body)))
        })
        .with(warp::trace::named("goodbye"));

    let routes = hello.or(goodbye).with(warp::trace::request());

    warp::serve(routes).run(([127, 0, 0, 1], 3030)).await;
}

warp.log

     Running `target/debug/warp-tracing`
2021-12-02T18:13:05.969237Z  INFO Server::run{addr=127.0.0.1:3030}: warp::server: listening on http://127.0.0.1:3030
2021-12-02T18:13:22.131648Z DEBUG request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}: warp::filters::trace: received request
2021-12-02T18:13:22.131692Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}: warp::filters::trace: processing request
2021-12-02T18:13:22.131725Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{hello}: warp::filters::trace: processing request
2021-12-02T18:13:22.131810Z  WARN request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{hello}: warp::filters::trace: unable to serve request (client error) status=404 error=Rejection(NotFound)
2021-12-02T18:13:22.131862Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{goodbye}: warp::filters::trace: processing request
2021-12-02T18:13:22.131892Z DEBUG request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{hello}: warp::filters::trace: close time.busy=73.6µs time.idle=98.6µs
in goodbye
will return body
2021-12-02T18:13:22.131940Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{goodbye}: warp::filters::trace: finished processing with success status=200
2021-12-02T18:13:22.131979Z DEBUG request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}:context{goodbye}: warp::filters::trace: close time.busy=85.0µs time.idle=43.1µs
2021-12-02T18:13:22.132004Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}: warp::filters::trace: finished processing with success status=200
2021-12-02T18:13:22.132026Z  INFO request{method=GET path=/goodbye version=HTTP/1.1 remote.addr=127.0.0.1:43980}: warp::filters::trace: close time.busy=301µs time.idle=109µs
sending chunk
sending chunk
sending chunk