From 9f266ee1a85cbe6a9f7dfbbd572ae52132dbddd5 Mon Sep 17 00:00:00 2001
From: sam <sam@sleepycat.moe>
Date: Wed, 20 Sep 2023 03:40:07 +0200
Subject: [PATCH] feat(backend): also add sentry tracing

---
 backend/main.go          |  8 +++-
 backend/server/errors.go | 15 ++-----
 backend/server/sentry.go | 89 ++++++++++++++++++++++++++++++++++++++++
 backend/server/server.go |  3 ++
 4 files changed, 102 insertions(+), 13 deletions(-)
 create mode 100644 backend/server/sentry.go

diff --git a/backend/main.go b/backend/main.go
index 0cb68a8..3d9395b 100644
--- a/backend/main.go
+++ b/backend/main.go
@@ -27,8 +27,12 @@ func run(c *cli.Context) error {
 	// initialize sentry
 	if dsn := os.Getenv("SENTRY_DSN"); dsn != "" {
 		sentry.Init(sentry.ClientOptions{
-			Dsn:     dsn,
-			Release: server.Tag,
+			Dsn:                dsn,
+			Debug:              true,
+			Release:            server.Tag,
+			EnableTracing:      true,
+			TracesSampleRate:   1.0,
+			ProfilesSampleRate: 1.0,
 		})
 	}
 
diff --git a/backend/server/errors.go b/backend/server/errors.go
index ba33050..299ea63 100644
--- a/backend/server/errors.go
+++ b/backend/server/errors.go
@@ -1,7 +1,6 @@
 package server
 
 import (
-	"context"
 	"fmt"
 	"net/http"
 
@@ -15,16 +14,10 @@ import (
 // The inner HandlerFunc additionally returns an error.
 func WrapHandler(hn func(w http.ResponseWriter, r *http.Request) error) http.HandlerFunc {
 	return func(w http.ResponseWriter, r *http.Request) {
-		hub := sentry.CurrentHub().Clone()
-
-		defer func(hub *sentry.Hub, r *http.Request) {
-			if err := recover(); err != nil {
-				hub.RecoverWithContext(
-					context.WithValue(r.Context(), sentry.RequestContextKey, r),
-					err,
-				)
-			}
-		}(hub, r)
+		hub := sentry.GetHubFromContext(r.Context())
+		if hub == nil {
+			hub = sentry.CurrentHub().Clone()
+		}
 
 		err := hn(w, r)
 		if err != nil {
diff --git a/backend/server/sentry.go b/backend/server/sentry.go
new file mode 100644
index 0000000..9641dec
--- /dev/null
+++ b/backend/server/sentry.go
@@ -0,0 +1,89 @@
+package server
+
+import (
+	"context"
+	"fmt"
+	"net/http"
+
+	"github.com/getsentry/sentry-go"
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+)
+
+func (s *Server) sentry(handler http.Handler) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
+
+		ctx := r.Context()
+		hub := sentry.GetHubFromContext(ctx)
+		if hub == nil {
+			hub = sentry.CurrentHub().Clone()
+			ctx = sentry.SetHubOnContext(ctx, hub)
+		}
+
+		options := []sentry.SpanOption{
+			sentry.WithOpName("http.server"),
+			sentry.ContinueFromRequest(r),
+			sentry.WithTransactionSource(sentry.SourceURL),
+		}
+		// We don't mind getting an existing transaction back so we don't need to
+		// check if it is.
+		transaction := sentry.StartTransaction(ctx,
+			fmt.Sprintf("%s %s", r.Method, r.URL.Path),
+			options...,
+		)
+		defer transaction.Finish()
+		r = r.WithContext(transaction.Context())
+		hub.Scope().SetRequest(r)
+		defer recoverWithSentry(hub, r)
+		handler.ServeHTTP(ww, r)
+
+		transaction.Status = httpStatusToSentryStatus(ww.Status())
+		rctx := chi.RouteContext(r.Context())
+		transaction.Name = rctx.RouteMethod + " " + rctx.RoutePattern()
+	})
+}
+
+func recoverWithSentry(hub *sentry.Hub, r *http.Request) {
+	if err := recover(); err != nil {
+		hub.RecoverWithContext(
+			context.WithValue(r.Context(), sentry.RequestContextKey, r),
+			err,
+		)
+	}
+}
+
+func httpStatusToSentryStatus(status int) sentry.SpanStatus {
+	// c.f. https://develop.sentry.dev/sdk/event-payloads/span/
+
+	if status >= 200 && status < 400 {
+		return sentry.SpanStatusOK
+	}
+
+	switch status {
+	case 499:
+		return sentry.SpanStatusCanceled
+	case 500:
+		return sentry.SpanStatusInternalError
+	case 400:
+		return sentry.SpanStatusInvalidArgument
+	case 504:
+		return sentry.SpanStatusDeadlineExceeded
+	case 404:
+		return sentry.SpanStatusNotFound
+	case 409:
+		return sentry.SpanStatusAlreadyExists
+	case 403:
+		return sentry.SpanStatusPermissionDenied
+	case 429:
+		return sentry.SpanStatusResourceExhausted
+	case 501:
+		return sentry.SpanStatusUnimplemented
+	case 503:
+		return sentry.SpanStatusUnavailable
+	case 401:
+		return sentry.SpanStatusUnauthenticated
+	default:
+		return sentry.SpanStatusUnknown
+	}
+}
diff --git a/backend/server/server.go b/backend/server/server.go
index 399ead0..bfc785d 100644
--- a/backend/server/server.go
+++ b/backend/server/server.go
@@ -50,6 +50,9 @@ func New() (*Server, error) {
 		s.Router.Use(middleware.Logger)
 	}
 	s.Router.Use(middleware.Recoverer)
+	// add Sentry tracing handler
+	s.Router.Use(s.sentry)
+
 	// add CORS
 	s.Router.Use(cors.Handler(cors.Options{
 		AllowedOrigins: []string{"https://*", "http://*"},