Returns zero and loses messages

[voscob]

Hey Andrew,

Can you tell me what I'm doing wrong? From time to time the PopFront method returns nil, and some messages get lost?

Thank you!

package somepackage

import (
	"sync"
	"testing"
	"time"

	"github.com/gammazero/deque"
	"github.com/google/uuid"
	"github.com/jpillora/backoff"
)

func Test(t *testing.T) {
	dq := deque.New[*string]()

	count := 15000

	m := make([]*string, 0, count)

	wg := sync.WaitGroup{}
	wg.Add(2)

	go func() {
		for i := 0; i < count; i++ {
			if i%3000 == 0 {
				b := &backoff.Backoff{
					Factor: 2,
					Min:    time.Second * 2,
					Max:    time.Second * 10,
				}

				time.Sleep(b.Duration())
			}

			s := uuid.New().String()
			dq.PushBack(&s)
		}

		wg.Done()
	}()

	go func() {
		for {
			if len(m) == count {
				break
			}

			if dq.Len() == 0 {
				continue
			}

			s := dq.PopFront()
			if s == nil {
			} // sometime it's true

			m = append(m, s)
		}
		wg.Done()
	}()

	wg.Wait()
}

[voscob]

UPD: I started working with sync.Mutex and the problem went away.

[gammazero]

Thank you for the follow-up. For maximum speed, this deque implementation leaves concurrency safety up to the application to provide, in whatever way the application chooses, if needed at all.