feat: Move from datadog to generic otel (#1567)

coderd/tracing/httpmw.go

@@ -0,0 +1,68 @@
+package tracing
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/go-chi/chi/middleware"
+	"github.com/go-chi/chi/v5"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+)
+
+// HTTPMW adds tracing to http routes.
+func HTTPMW(tracerProvider *sdktrace.TracerProvider, name string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+			// do not trace if exporter has not be initialized
+			if tracerProvider == nil {
+				next.ServeHTTP(rw, r)
+				return
+			}
+
+			// start span with default span name. Span name will be updated to "method route" format once request finishes.
+			_, span := tracerProvider.Tracer(name).Start(r.Context(), fmt.Sprintf("%s %s", r.Method, r.RequestURI))
+			defer span.End()
+
+			wrw := middleware.NewWrapResponseWriter(rw, r.ProtoMajor)
+
+			// pass the span through the request context and serve the request to the next middleware
+			next.ServeHTTP(rw, r)
+
+			// set the resource name as we get it only once the handler is executed
+			route := chi.RouteContext(r.Context()).RoutePattern()
+			if route != "" {
+				span.SetName(fmt.Sprintf("%s %s", r.Method, route))
+			}
+			span.SetAttributes(attribute.KeyValue{
+				Key:   "http.method",
+				Value: attribute.StringValue(r.Method),
+			})
+			span.SetAttributes(attribute.KeyValue{
+				Key:   "http.route",
+				Value: attribute.StringValue(route),
+			})
+			span.SetAttributes(attribute.KeyValue{
+				Key:   "http.path",
+				Value: attribute.StringValue(r.URL.EscapedPath()),
+			})
+
+			// set the status code
+			status := wrw.Status()
+			// 0 status means one has not yet been sent in which case net/http library will write StatusOK
+			if status == 0 {
+				status = http.StatusOK
+			}
+			span.SetAttributes(attribute.KeyValue{
+				Key:   "http.status_code",
+				Value: attribute.IntValue(status),
+			})
+
+			// if 5XX we set the span to "error" status
+			if status >= 500 {
+				span.SetStatus(codes.Error, fmt.Sprintf("%d: %s", status, http.StatusText(status)))
+			}
+		})
+	}
+}