Use correct semantic conventions for trace labels

The OpenTelemetry spec defines the semantic conventions that HTTP services should use for the labels included in traces: https://opentelemetry.io/docs/specs/semconv/http/http-spans/

Previously, we were using an outdated version of this spec for the OpenCensus traces. This updates the labels to match the current spec.

The notable changes updates to the path for HTTP method and status code, the fields that include the URL parts, and more rigorously following the standard for propagating the Host header.

Signed-off-by: Scott Fleener <[email protected]>

linkerd/trace-context/src/service.rs

@@ -1,5 +1,6 @@
 use crate::{propagation, Span, SpanSink};
 use futures::{future::Either, prelude::*};
+use http::Uri;
 use linkerd_stack::layer;
 use std::{
     collections::HashMap,
@@ -35,20 +36,35 @@ impl<K: Clone, S> TraceContext<K, S> {
     }
 
     fn request_labels<B>(req: &http::Request<B>) -> HashMap<&'static str, String> {
-        let mut labels = HashMap::with_capacity(5);
-        labels.insert("http.method", format!("{}", req.method()));
-        let path = req
-            .uri()
-            .path_and_query()
-            .map(|pq| pq.as_str().to_owned())
-            .unwrap_or_default();
-        labels.insert("http.path", path);
-        if let Some(authority) = req.uri().authority() {
-            labels.insert("http.authority", authority.as_str().to_string());
+        let mut labels = HashMap::with_capacity(6);
+        labels.insert("http.request.method", format!("{}", req.method()));
+        let url = req.uri();
+        if let Some(scheme) = url.scheme_str() {
+            labels.insert("url.scheme", scheme.to_string());
         }
-        if let Some(host) = req.headers().get("host") {
+        labels.insert("url.path", url.path().to_string());
+        if let Some(query) = url.query() {
+            labels.insert("url.query", query.to_string());
+        }
+
+        // This is the order of precendence for host headers,
+        // see https://opentelemetry.io/docs/specs/semconv/http/http-spans/
+        let host_header = req
+            .headers()
+            .get("X-Forwarded-Host")
+            .or_else(|| req.headers().get(":authority"))
+            .or_else(|| req.headers().get("host"));
+
+        if let Some(host) = host_header {
             if let Ok(host) = host.to_str() {
-                labels.insert("http.host", host.to_string());
+                if let Ok(uri) = host.parse::<Uri>() {
+                    if let Some(host) = uri.host() {
+                        labels.insert("server.address", host.to_string());
+                    }
+                    if let Some(port) = uri.port() {
+                        labels.insert("server.port", port.to_string());
+                    }
+                }
             }
         }
         labels
@@ -58,7 +74,10 @@ impl<K: Clone, S> TraceContext<K, S> {
         mut labels: HashMap<&'static str, String>,
         rsp: &http::Response<B>,
     ) -> HashMap<&'static str, String> {
-        labels.insert("http.status_code", rsp.status().as_str().to_string());
+        labels.insert(
+            "http.response.status_code",
+            rsp.status().as_str().to_string(),
+        );
         labels
     }
 }