Go green tea

1.txt

# Start with Green tea
$GOEXPERIMENT=greenteagc go run main.go

2025/08/27 11:01:27 pprof server on :6060
2025/08/27 11:01:27 Server running on :8080 with Green Tea GC enabled
/gc/heap/allocs:bytes = {1 2402052896 <nil>}
/gc/heap/frees:bytes = {1 2396205576 <nil>}
/gc/heap/allocs:objects = {1 22943712 <nil>}
/gc/heap/frees:objects = {1 22922079 <nil>}
/gc/heap/live:bytes = {1 5356376 <nil>}
/gc/cycles/total:gc-cycles = {1 539 <nil>}
/gc/pauses:seconds = {3 0 0x14001324390}


# Load test
$wrk -t12 -c400 -d30s http://localhost:8080/items

Running 30s test @ http://localhost:8080/items
  12 threads and 400 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     9.23ms   12.79ms 327.11ms   92.51%
    Req/Sec     4.78k     0.96k    8.06k    87.00%
  1714201 requests in 30.07s, 9.02GB read
  Socket errors: connect 0, read 337, write 0, timeout 0
Requests/sec:  57003.43
Transfer/sec:    307.04MB

main.go

package main

import (
	"encoding/json"
	"fmt"
	"log"
	"math/rand"
	"net/http"
	"runtime/metrics"
	"time"

	_ "net/http/pprof" // enables /debug/pprof
)

type Item struct {
	ID    int
	Name  string
	Value float64
}

// handler simulates creating many small objects per request
func handler(w http.ResponseWriter, r *http.Request) {
	var items []Item
	for i := 0; i < 100; i++ { // allocate lots of small structs
		items = append(items, Item{
			ID:    i,
			Name:  randomString(8),
			Value: rand.Float64(),
		})
	}
	w.Header().Set("Content-Type", "application/json")
	json.NewEncoder(w).Encode(items)
}

// randomString generates small temporary strings
func randomString(n int) string {
	letters := []rune("abcdefghijklmnopqrstuvwxyz")
	s := make([]rune, n)
	for i := range s {
		s[i] = letters[rand.Intn(len(letters))]
	}
	return string(s)
}

func logGCMetrics() {
	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	samples := []metrics.Sample{
		{Name: "/gc/heap/allocs:bytes"},
		{Name: "/gc/heap/frees:bytes"},
		{Name: "/gc/heap/allocs:objects"},
		{Name: "/gc/heap/frees:objects"},
		{Name: "/gc/heap/live:bytes"},
		{Name: "/gc/cycles/total:gc-cycles"},
		{Name: "/gc/pauses:seconds"},
	}

	for range ticker.C {
		metrics.Read(samples)
		for _, s := range samples {
			fmt.Printf("%s = %v\n", s.Name, s.Value)
		}
		fmt.Println("----")
	}
}

func main() {

	go logGCMetrics()

	go func() {
		log.Println("pprof server on :6060")
		log.Println(http.ListenAndServe("localhost:6060", nil))
	}()

	rand.Seed(time.Now().UnixNano())
	http.HandleFunc("/items", handler)
	log.Println("Server running on :8080 with Green Tea GC enabled")
	log.Fatal(http.ListenAndServe(":8080", nil))
}