From 213628b9585eefaa7c6caff16d4afa8a656d2470 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 12:55:23 +0100
Subject: [PATCH] Debug Health route latency.

---
 internal/api/health.go | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/internal/api/health.go b/internal/api/health.go
index 5c2699f..3da4121 100644
--- a/internal/api/health.go
+++ b/internal/api/health.go
@@ -1,13 +1,18 @@
 package api
 
 import (
+	"context"
 	"errors"
 	"fmt"
+	"github.com/coreos/go-systemd/v22/daemon"
 	"github.com/openHPI/poseidon/internal/config"
 	"github.com/openHPI/poseidon/internal/environment"
 	"github.com/openHPI/poseidon/pkg/dto"
 	"net/http"
+	"os"
+	"runtime/pprof"
 	"strings"
+	"time"
 )
 
 var ErrorPrewarmingPoolDepleting = errors.New("the prewarming pool is depleting")
@@ -17,6 +22,10 @@ var ErrorPrewarmingPoolDepleting = errors.New("the prewarming pool is depleting"
 // If it is not, the response won't reach the client.
 func Health(manager environment.Manager) http.HandlerFunc {
 	return func(writer http.ResponseWriter, request *http.Request) {
+		ctx, cancel := context.WithCancel(request.Context())
+		defer cancel()
+		go debugGoroutines(ctx)
+
 		if err := checkPrewarmingPool(manager); err != nil {
 			sendJSON(writer, &dto.InternalServerError{Message: err.Error(), ErrorCode: dto.PrewarmingPoolDepleting},
 				http.StatusServiceUnavailable, request.Context())
@@ -40,3 +49,24 @@ func checkPrewarmingPool(manager environment.Manager) error {
 	}
 	return nil
 }
+
+// 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")
+		}
+	}
+}