feat: add basic prometheus metrics integration

internal/proxy/director/layer/queue/debouncer.go

@@ -0,0 +1,73 @@
+package queue
+
+import (
+	"sync"
+	"time"
+
+	"github.com/pkg/errors"
+)
+
+type DebouncerMap struct {
+	debouncers sync.Map
+}
+
+func NewDebouncerMap() *DebouncerMap {
+	return &DebouncerMap{
+		debouncers: sync.Map{},
+	}
+}
+
+func (m *DebouncerMap) Do(key string, after time.Duration, fn func()) {
+	newDebouncer := NewDebouncer(after)
+	rawDebouncer, loaded := m.debouncers.LoadOrStore(key, newDebouncer)
+
+	debouncer, ok := rawDebouncer.(*Debouncer)
+	if !ok {
+		panic(errors.Errorf("unexpected debouncer value, expected '%T', got '%T'", newDebouncer, rawDebouncer))
+	}
+
+	if loaded {
+		debouncer.Update(after)
+	}
+
+	debouncer.Do(fn)
+}
+
+func NewDebouncer(after time.Duration) *Debouncer {
+	return &Debouncer{after: after}
+}
+
+type Debouncer struct {
+	mu    sync.Mutex
+	after time.Duration
+	timer *time.Timer
+	fn    func()
+}
+
+func (d *Debouncer) Do(fn func()) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if d.timer != nil {
+		d.timer.Stop()
+	}
+
+	d.fn = fn
+	d.timer = time.AfterFunc(d.after, d.fn)
+}
+
+func (d *Debouncer) Update(after time.Duration) {
+	d.mu.Lock()
+	defer d.mu.Unlock()
+
+	if after == d.after {
+		return
+	}
+
+	if d.timer != nil {
+		d.timer.Stop()
+	}
+
+	d.after = after
+	d.timer = time.AfterFunc(d.after, d.fn)
+}