From ae86b1c261f6332a8d07458803c47ab7010a1d6b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Maximilian=20Pa=C3=9F?=
 <22845248+mpass99@users.noreply.github.com>
Date: Fri, 26 Jan 2024 22:38:52 +0100
Subject: [PATCH] Debug HTTPLoggingMiddleware latency.

---
 pkg/logging/logging.go | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/pkg/logging/logging.go b/pkg/logging/logging.go
index 821b664..4b26d58 100644
--- a/pkg/logging/logging.go
+++ b/pkg/logging/logging.go
@@ -2,13 +2,16 @@ package logging
 
 import (
 	"bufio"
+	"context"
 	"fmt"
+	"github.com/coreos/go-systemd/v22/daemon"
 	"github.com/getsentry/sentry-go"
 	"github.com/openHPI/poseidon/pkg/dto"
 	"github.com/sirupsen/logrus"
 	"net"
 	"net/http"
 	"os"
+	"runtime/pprof"
 	"strings"
 	"time"
 )
@@ -82,6 +85,12 @@ func HTTPLoggingMiddleware(next http.Handler) http.Handler {
 		start := time.Now().UTC()
 		path := RemoveNewlineSymbol(r.URL.Path)
 
+		if path == "/api/v1/health" {
+			ctx, cancel := context.WithCancel(r.Context())
+			defer cancel()
+			go debugGoroutines(ctx)
+		}
+
 		lrw := NewLoggingResponseWriter(w)
 		next.ServeHTTP(lrw, r)
 
@@ -107,3 +116,24 @@ func RemoveNewlineSymbol(data string) string {
 	data = strings.ReplaceAll(data, "\n", "")
 	return data
 }
+
+// debugGoroutines temporarily debugs a behavior where we observe long latencies in the Health route.
+func debugGoroutines(ctx context.Context) {
+	interval, err := daemon.SdWatchdogEnabled(false)
+	if err != nil || interval == 0 {
+		return
+	}
+	log.Trace("Starting timeout for debugging the Goroutines")
+
+	const notificationIntervalFactor = 3
+	select {
+	case <-ctx.Done():
+		return
+	case <-time.After(interval / notificationIntervalFactor):
+		log.Warn("Health route latency is too high")
+		err := pprof.Lookup("goroutine").WriteTo(os.Stderr, 1)
+		if err != nil {
+			log.WithError(err).Warn("Failed to log the goroutines")
+		}
+	}
+}