jitter: add NewTickerContext

Signed-off-by: Vasiliy Tolstov <v.tolstov@unistack.org>

util/jitter/ticker_test.go

@@ -0,0 +1,62 @@
+package jitter
+
+import (
+	"context"
+	"testing"
+	"time"
+)
+
+func TestNewTickerContext(t *testing.T) {
+	t.Parallel()
+	ctx, cancel := context.WithTimeout(context.Background(), 500*time.Millisecond)
+	defer cancel()
+
+	ticker := NewTickerContext(ctx, 600*time.Millisecond, 1000*time.Millisecond)
+	defer ticker.Stop()
+loop:
+	for {
+		select {
+		case <-ctx.Done():
+			ticker.Stop()
+			break loop
+		case v, ok := <-ticker.C:
+			if ok {
+				t.Fatalf("context must be closed %s", v)
+			}
+			break loop
+		}
+	}
+}
+
+func TestTicker(t *testing.T) {
+	t.Parallel()
+
+	min := time.Duration(10)
+	max := time.Duration(20)
+
+	// tick can take a little longer since we're not adjusting it to account for
+	// processing.
+	precision := time.Duration(4)
+
+	rt := NewTicker(min*time.Millisecond, max*time.Millisecond)
+	for i := 0; i < 5; i++ {
+		t0 := time.Now()
+		t1 := <-rt.C
+		td := t1.Sub(t0)
+		if td < min*time.Millisecond {
+			t.Fatalf("tick was shorter than expected: %s", td)
+		} else if td > (max+precision)*time.Millisecond {
+			t.Fatalf("tick was longer than expected: %s", td)
+		}
+	}
+	rt.Stop()
+	time.Sleep((max + precision) * time.Millisecond)
+	select {
+	case v, ok := <-rt.C:
+		if ok || !v.IsZero() {
+			t.Fatal("ticker did not shut down")
+		}
+	default:
+		t.Fatal("expected to receive close channel signal")
+	}
+}