add telemetry pkg

f0ssel · f0ssel · commit e0e433ccb17a · 2022-05-18T18:53:34.000Z
diff --git a/telemetry/exporter.go b/telemetry/exporter.go
@@ -0,0 +1,40 @@
+package telemetry
+
+import (
+	"context"
+
+	"go.opentelemetry.io/otel"
+	"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"
+)
+
+// Exporter creates a grpc otlp exporter and sets it as the global trace provider.
+// Caller is responsible for closing exporter to ensure all data is flushed.
+func Exporter(ctx context.Context, service string) (func(), error) {
+	res, err := resource.New(ctx,
+		resource.WithAttributes(
+			// the service name used to display traces in backends
+			semconv.ServiceNameKey.String(service),
+		),
+	)
+
+	otlptracegrpc.NewClient()
+	exporter, err := otlptrace.New(ctx, otlptracegrpc.NewClient())
+	if err != nil {
+		return nil, xerrors.Errorf("creating otlp exporter: %w", err)
+	}
+
+	tracerProvider := sdktrace.NewTracerProvider(
+		sdktrace.WithBatcher(exporter),
+		sdktrace.WithResource(res),
+	)
+	otel.SetTracerProvider(tracerProvider)
+
+	return func() {
+		_ = tracerProvider.Shutdown(ctx)
+	}, nil
+}
diff --git a/telemetry/httpmw.go b/telemetry/httpmw.go
@@ -0,0 +1,52 @@
+package telemetry
+
+import (
+	"fmt"
+	"net/http"
+
+	"github.com/go-chi/chi/middleware"
+	"github.com/go-chi/chi/v5"
+	"go.opentelemetry.io/otel"
+	"go.opentelemetry.io/otel/attribute"
+	"go.opentelemetry.io/otel/codes"
+)
+
+// HTTPMW adds tracing to http routes.
+func HTTPMW(tracer string) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(rw http.ResponseWriter, r *http.Request) {
+			// start span with default span name. Span name will be updated once request finishes
+			_, span := otel.Tracer(tracer).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
+			resourceName := chi.RouteContext(r.Context()).RoutePattern()
+			if resourceName == "" {
+				resourceName = "unknown"
+			}
+			resourceName = r.Method + " " + resourceName
+			span.SetName(resourceName)
+
+			// 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)))
+			}
+		})
+	}
+}
