(new): v1.2 release

observer_async.go

@@ -0,0 +1,100 @@
+package laniakea
+
+import (
+	"context"
+	"fmt"
+	"sync"
+	"sync/atomic"
+
+	"git.scuroneko.dev/scuroneko/sneklog/v2"
+)
+
+const observerQueueSize = 1024
+
+type queuedObserverEvent struct {
+	ctx   context.Context
+	event Event
+}
+
+type observerDispatcher struct {
+	observer Observer
+	logger   *sneklog.Logger
+	queue    chan queuedObserverEvent
+	stop     chan struct{}
+	mu       sync.RWMutex
+	closed   bool
+	wg       sync.WaitGroup
+	stopOnce sync.Once
+	dropped  atomic.Uint64
+}
+
+func newObserverDispatcher(observer Observer, logger *sneklog.Logger) *observerDispatcher {
+	dispatcher := &observerDispatcher{
+		observer: observer,
+		logger:   logger,
+		queue:    make(chan queuedObserverEvent, observerQueueSize),
+		stop:     make(chan struct{}),
+	}
+	dispatcher.wg.Add(1)
+	go dispatcher.run()
+	return dispatcher
+}
+
+func (d *observerDispatcher) enqueue(ctx context.Context, event Event) {
+	if ctx == nil {
+		ctx = context.Background()
+	} else {
+		ctx = context.WithoutCancel(ctx)
+	}
+	d.mu.RLock()
+	defer d.mu.RUnlock()
+	if d.closed {
+		return
+	}
+	select {
+	case d.queue <- queuedObserverEvent{ctx: ctx, event: event}:
+	default:
+		dropped := d.dropped.Add(1)
+		if d.logger != nil && (dropped == 1 || dropped&(dropped-1) == 0) {
+			d.logger.Warnf("observer queue full; dropped %d events", dropped)
+		}
+	}
+}
+
+func (d *observerDispatcher) run() {
+	defer d.wg.Done()
+	for {
+		select {
+		case queued := <-d.queue:
+			d.dispatch(queued)
+		case <-d.stop:
+			for {
+				select {
+				case queued := <-d.queue:
+					d.dispatch(queued)
+				default:
+					return
+				}
+			}
+		}
+	}
+}
+
+func (d *observerDispatcher) dispatch(queued queuedObserverEvent) {
+	defer func() {
+		if recovered := recover(); recovered != nil && d.logger != nil {
+			d.logger.Errorln(fmt.Sprintf("panic in observer: %v", recovered))
+		}
+	}()
+	emitObserverEvent(d.observer, queued.ctx, queued.event)
+}
+
+func (d *observerDispatcher) close() {
+	d.stopOnce.Do(func() {
+		d.mu.Lock()
+		d.closed = true
+		close(d.stop)
+		d.mu.Unlock()
+	})
+	d.wg.Wait()
+}