rename to tracing for real

f0ssel · f0ssel · commit 776d8fc94736 · 2022-05-18T21:14:44.000Z
diff --git a/tracing/exporter.go b/tracing/exporter.go
@@ -0,0 +1,41 @@
+package tracing
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace"
+	"go.opentelemetry.io/otel/exporters/otlp/otlptrace/otlptracegrpc"
+	"go.opentelemetry.io/otel/sdk/resource"
+	sdktrace "go.opentelemetry.io/otel/sdk/trace"
+	semconv "go.opentelemetry.io/otel/semconv/v1.4.0"
+	"golang.org/x/xerrors"
+)
+
+// TracerProvider creates a grpc otlp exporter and configures a trace provider.
+// Caller is responsible for calling TracerProvider.Shutdown to ensure all data is flushed.
+func TracerProvider(ctx context.Context, service string) (*sdktrace.TracerProvider, error) {
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			// the service name used to display traces in backends
+			semconv.ServiceNameKey.String(service),
+		),
+	)
+	if err != nil {
+		return nil, xerrors.Errorf("creating otlp resource: %w", err)
+	}
+
+	// By default we send span data to a local otel collector.
+	// The endpoint we push to can be configured with env vars.
+	// See https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/exporter.md
+	exporter, err := otlptrace.New(ctx, otlptracegrpc.NewClient(otlptracegrpc.WithInsecure()))
+	if err != nil {
+		return nil, xerrors.Errorf("creating otlp exporter: %w", err)
+	}
+
+	tracerProvider := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+		sdktrace.WithResource(res),
+	)
+
+	return tracerProvider, nil
+}
diff --git a/tracing/httpmw.go b/tracing/httpmw.go
@@ -0,0 +1,69 @@
+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 once request finishes
+			_, span := tracerProvider.Tracer(name).Start(r.Context(), "http.request")
+			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 == "" {
+				route = "unknown"
+			}
+			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)))
+			}
+		})
+	}
+}
