A small demo to show go's pprof doesn't track tags for heap

Author: ringerc

go/http_pprof_test/go.mod

@@ -0,0 +1,3 @@
+module http_pprof_test
+
+go 1.23.2

go/http_pprof_test/main.go

@@ -0,0 +1,58 @@
+package main
+
+import (
+	"context"
+	"fmt"
+	"log"
+	"net/http"
+	_ "net/http/pprof"
+	"runtime/pprof"
+	"sync"
+	"time"
+)
+
+func oneWorkItem(_ context.Context, leakySliceEntry []string) {
+	fmt.Printf("Start: %v\n", time.Now())
+
+	// Memory
+	for i := 0; i < 500000; i++ {
+		leakySliceEntry = append(leakySliceEntry, "aaaa")
+	}
+
+	// Blocking
+	time.Sleep(2 * time.Second)
+	fmt.Printf("End: %v\n", time.Now())
+}
+
+// Some function that does work
+func hardWork(ctx context.Context, wg *sync.WaitGroup, leakySlice [][]string) {
+	defer wg.Done()
+
+	var counter int
+	for {
+		pprof.Do(ctx,
+			pprof.Labels("instance", fmt.Sprintf("instance%d", counter)),
+			func(ctx context.Context) {
+				leakySliceEntry := make([]string, 0)
+				leakySlice = append(leakySlice, leakySliceEntry)
+				oneWorkItem(ctx, leakySliceEntry)
+			})
+		counter++
+	}
+}
+
+func main() {
+	var wg sync.WaitGroup
+	wg.Add(1)
+	go func() {
+		fmt.Println("Listening on localhost:6060 for pprof, use \"go tool pprof -seconds 5 http://localhost:6060/debug/pprof/heap\" to check heap profile.")
+		log.Printf("Listener started: %s\n", http.ListenAndServe("localhost:6060", nil))
+		fmt.Println("Done listening")
+		wg.Done()
+	}()
+	wg.Add(1)
+	ctx := pprof.WithLabels(context.Background(), pprof.Labels("name", "hardWork"))
+	var leakySlice [][]string
+	go hardWork(ctx, &wg, leakySlice)
+	wg.Wait()
+}