fix otel http instrumentation span naming (#2)

Reviewed-on: #2
Co-authored-by: Ryan D McGuire <ryand_mcguire@sweetwater.com>
Co-committed-by: Ryan D McGuire <ryand_mcguire@sweetwater.com>

pkg/srv/http/http.go

@@ -10,6 +10,7 @@ import (
 	"net"
 	"net/http"
 	"os"
+	"regexp"
 	"strings"
 	"time"
 
@@ -25,11 +26,12 @@ import (
 )
 
 var (
-	httpMeter       metric.Meter
-	httpTracer      trace.Tracer
-	defReadTimeout  = 10 * time.Second
-	defWriteTimeout = 10 * time.Second
-	defIdleTimeout  = 15 * time.Second
+	httpMeter                   metric.Meter
+	httpTracer                  trace.Tracer
+	httpPatternWithMethodRegexp = regexp.MustCompile(`(\w+) .*`)
+	defReadTimeout              = 10 * time.Second
+	defWriteTimeout             = 10 * time.Second
+	defIdleTimeout              = 15 * time.Second
 )
 
 func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
@@ -39,19 +41,12 @@ func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
 		mux = &http.ServeMux{}
 	)
 
-	// NOTE: Wraps handle func with otelhttp handler and
-	// inserts route tag
-	otelHandleFunc := func(pattern string, handlerFunc func(http.ResponseWriter, *http.Request)) {
-		handler := otelhttp.WithRouteTag(pattern, http.HandlerFunc(handlerFunc))
-		mux.Handle(pattern, handler) // Associate pattern with handler
-	}
-
 	healthChecks := handleHealthCheckFunc(opts.Ctx, opts.HealthChecks...)
-	otelHandleFunc("/health", healthChecks)
-	otelHandleFunc("/", healthChecks)
+	mux.HandleFunc("/health", healthChecks)
+	mux.HandleFunc("/", healthChecks)
 
 	for _, f := range opts.Funcs {
-		otelHandleFunc(f.Path, f.HandlerFunc)
+		mux.HandleFunc(f.Path, f.HandlerFunc)
 	}
 
 	// Prometheus metrics endpoint
@@ -74,12 +69,12 @@ func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
 		if h.StripPrefix {
 			h.Handler = http.StripPrefix(h.Prefix[:len(h.Prefix)-1], h.Handler)
 		}
-		mux.Handle(h.Prefix, h.Handler)
+		mux.Handle(h.Prefix, otelhttp.WithRouteTag(h.Prefix, h.Handler))
 	}
 
-	// Add OTEL, skip health-check spans
-	// NOTE: Add any other span exclusions here
+	// Add OTEL instrumentation, filter noise, set span names
 	handler := otelhttp.NewHandler(mux, "/",
+		// TODO: Make configurable similar to config.http.LogExcludePathRegexps
 		otelhttp.WithFilter(func(r *http.Request) bool {
 			switch r.URL.Path {
 			case "/health":
@@ -89,6 +84,18 @@ func prepHTTPServer(opts *opts.AppHTTP) *http.Server {
 			default:
 				return true
 			}
+		}),
+		otelhttp.WithSpanNameFormatter(func(operation string, r *http.Request) string {
+			endpoint := r.URL.Path
+			if _, pattern := mux.Handler(r); pattern != "" {
+				endpoint = pattern
+			}
+
+			if httpPatternWithMethodRegexp.MatchString(endpoint) {
+				return endpoint
+			}
+
+			return fmt.Sprintf("%s %s", r.Method, endpoint)
 		}))
 
 	// Set timeouts from defaults, override