Stop stale query work promptly on generation cancel

2 files changed, 61 insertions, 0 deletions

diff --git a/internal/ctxutil/sleep.go b/internal/ctxutil/sleep.go
new file mode 100644
index 0000000..6965e8d
--- /dev/null
+++ b/internal/ctxutil/sleep.go
@@ -0,0 +1,29 @@
+package ctxutil
+
+import (
+	"context"
+	"time"
+)
+
+// Sleep waits for the delay or exits early when the context is canceled.
+// It returns true when the full delay elapsed.
+func Sleep(ctx context.Context, delay time.Duration) bool {
+	if delay <= 0 {
+		select {
+		case <-ctx.Done():
+			return false
+		default:
+			return true
+		}
+	}
+
+	timer := time.NewTimer(delay)
+	defer timer.Stop()
+
+	select {
+	case <-ctx.Done():
+		return false
+	case <-timer.C:
+		return true
+	}
+}
diff --git a/internal/ctxutil/sleep_test.go b/internal/ctxutil/sleep_test.go
new file mode 100644
index 0000000..f32b22c
--- /dev/null
+++ b/internal/ctxutil/sleep_test.go
@@ -0,0 +1,32 @@
+package ctxutil
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestSleepReturnsEarlyOnCancel(t *testing.T) {
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+
+	start := time.Now()
+	if Sleep(ctx, time.Second) {
+		t.Fatal("Sleep should stop when the context is canceled")
+	}
+	if elapsed := time.Since(start); elapsed > 50*time.Millisecond {
+		t.Fatalf("Sleep took too long to return after cancellation: %v", elapsed)
+	}
+}
+
+func TestSleepWaitsForDelay(t *testing.T) {
+	ctx := context.Background()
+
+	start := time.Now()
+	if !Sleep(ctx, 20*time.Millisecond) {
+		t.Fatal("Sleep should report success when the delay elapses")
+	}
+	if elapsed := time.Since(start); elapsed < 15*time.Millisecond {
+		t.Fatalf("Sleep returned too early: %v", elapsed)
+	}
+}