Initial DDC release

internal/jobs/slots.go

@@ -0,0 +1,45 @@
+package jobs
+
+import (
+	"context"
+	"sync"
+	"time"
+)
+
+const slotWaitInterval = 500 * time.Millisecond
+
+type slotLimiter struct {
+	mutex  sync.Mutex
+	active int
+}
+
+func (limiter *slotLimiter) acquire(ctx context.Context, limit func() int) bool {
+	ticker := time.NewTicker(slotWaitInterval)
+	defer ticker.Stop()
+	for {
+		if limiter.tryAcquire(limit()) {
+			return true
+		}
+		select {
+		case <-ctx.Done():
+			return false
+		case <-ticker.C:
+		}
+	}
+}
+
+func (limiter *slotLimiter) tryAcquire(limit int) bool {
+	limiter.mutex.Lock()
+	defer limiter.mutex.Unlock()
+	if limiter.active >= limit {
+		return false
+	}
+	limiter.active++
+	return true
+}
+
+func (limiter *slotLimiter) release() {
+	limiter.mutex.Lock()
+	defer limiter.mutex.Unlock()
+	limiter.active--
+}