add a debug_span for dns resolution to disambiguate metrics

Author: joshka

Cargo.toml

@@ -38,6 +38,7 @@ http-body-util = "0.1.0"
 tokio = { version = "1", features = ["macros", "test-util", "signal"] }
 tokio-test = "0.4"
 pretty_env_logger = "0.5"
+tracing-subscriber = { version = "0.3.18", features = ["env-filter"] }
 
 [target.'cfg(any(target_os = "linux", target_os = "macos"))'.dev-dependencies]
 pnet_datalink = "0.35.0"

examples/client.rs

@@ -3,9 +3,23 @@ use std::env;
 use http_body_util::Empty;
 use hyper::Request;
 use hyper_util::client::legacy::{connect::HttpConnector, Client};
+use tracing::{info_span, Instrument};
+use tracing_subscriber::{
+    fmt::{self, format::FmtSpan},
+    prelude::*,
+    EnvFilter,
+};
 
 #[tokio::main(flavor = "current_thread")]
 async fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let fmt_layer = fmt::layer()
+        .with_span_events(FmtSpan::CLOSE) // show time elapsed in spans
+        .with_timer(fmt::time::Uptime::default());
+    tracing_subscriber::registry()
+        .with(EnvFilter::from_default_env())
+        .with(fmt_layer)
+        .init();
+
     let url = match env::args().nth(1) {
         Some(url) => url,
         None => {
@@ -28,7 +42,8 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
         .uri(url)
         .body(Empty::<bytes::Bytes>::new())?;
 
-    let resp = client.request(req).await?;
+    let span = info_span!("request", uri = %req.uri());
+    let resp = client.request(req).instrument(span).await?;
 
     eprintln!("{:?} {:?}", resp.version(), resp.status());
     eprintln!("{:#?}", resp.headers());

src/client/legacy/connect/dns.rs

@@ -31,7 +31,7 @@ use std::{fmt, io, vec};
 
 use tokio::task::JoinHandle;
 use tower_service::Service;
-use tracing::debug;
+use tracing::{debug, debug_span};
 
 pub(super) use self::sealed::Resolve;
 
@@ -118,10 +118,10 @@ impl Service<Name> for GaiResolver {
     }
 
     fn call(&mut self, name: Name) -> Self::Future {
-        let current_span = tracing::Span::current();
+        let span = debug_span!("resolve", host = %name.host).or_current();
         let blocking = tokio::task::spawn_blocking(move || {
-            let _enter = current_span.enter();
-            debug!("resolving host={:?}", name.host);
+            let _enter = span.enter();
+            debug!(host = name.host, "resolving");
             (&*name.host, 0)
                 .to_socket_addrs()
                 .map(|i| SocketAddrs { iter: i })