fix: use ticker time in sliding window

examples/aerospike/main.go

@@ -6,7 +6,6 @@ import (
 	"time"
 
 	ext "github.com/reugn/go-streams/aerospike"
-	"github.com/reugn/go-streams/util"
 
 	aero "github.com/aerospike/aerospike-client-go/v6"
 	"github.com/reugn/go-streams/flow"
@@ -50,7 +49,7 @@ func main() {
 
 var transform = func(msg *aero.Record) ext.AerospikeKeyBins {
 	log.Println(msg.Bins)
-	msg.Bins["ts"] = util.NowNano()
+	msg.Bins["ts"] = time.Now().UnixNano()
 	return ext.AerospikeKeyBins{
 		Key:  msg.Key,
 		Bins: msg.Bins,

examples/std/main.go

@@ -38,7 +38,7 @@ func tickerChan(repeat time.Duration) chan interface{} {
 	nc := make(chan interface{})
 	go func() {
 		for range oc {
-			nc <- &message{strconv.FormatInt(time.Now().UTC().UnixNano(), 10)}
+			nc <- &message{strconv.FormatInt(time.Now().UnixNano(), 10)}
 		}
 	}()
 	return nc

flow/queue_test.go

@@ -3,19 +3,19 @@ package flow_test
 import (
 	"container/heap"
 	"testing"
+	"time"
 
 	"github.com/reugn/go-streams/flow"
-	"github.com/reugn/go-streams/util"
 )
 
 func TestQueueOps(t *testing.T) {
 	queue := &flow.PriorityQueue{}
-	heap.Push(queue, flow.NewItem(1, util.NowNano(), 0))
+	heap.Push(queue, flow.NewItem(1, time.Now().UnixNano(), 0))
 	heap.Push(queue, flow.NewItem(2, 1234, 0))
-	heap.Push(queue, flow.NewItem(3, util.NowNano(), 0))
+	heap.Push(queue, flow.NewItem(3, time.Now().UnixNano(), 0))
 	queue.Swap(0, 1)
 	head := queue.Head()
-	queue.Update(head, util.NowNano())
+	queue.Update(head, time.Now().UnixNano())
 	first := heap.Pop(queue).(*flow.Item)
 
 	assertEquals(t, 2, first.Msg.(int))

flow/sliding_window.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/reugn/go-streams"
-	"github.com/reugn/go-streams/util"
 )
 
 // SlidingWindow assigns elements to windows of fixed length configured by the window
@@ -106,7 +105,7 @@ func (sw *SlidingWindow[T]) transmit(inlet streams.Inlet) {
 // It returns system clock time otherwise.
 func (sw *SlidingWindow[T]) timestamp(element T) int64 {
 	if sw.timestampExtractor == nil {
-		return util.NowNano()
+		return time.Now().UnixNano()
 	}
 	return sw.timestampExtractor(element)
 }
@@ -128,16 +127,17 @@ func (sw *SlidingWindow[T]) emit() {
 	// wait for the sliding window to start
 	time.Sleep(sw.windowSize - sw.slidingInterval)
 
+	lastTick := time.Now()
 	ticker := time.NewTicker(sw.slidingInterval)
 	defer ticker.Stop()
 
 	for {
 		select {
-		case <-ticker.C:
-			sw.dispatchWindow()
+		case lastTick = <-ticker.C:
+			sw.dispatchWindow(lastTick)
 
 		case <-sw.done:
-			sw.dispatchWindow()
+			sw.dispatchWindow(lastTick.Add(sw.slidingInterval))
 			close(sw.out)
 			return
 		}
@@ -146,11 +146,11 @@ func (sw *SlidingWindow[T]) emit() {
 
 // dispatchWindow creates a new window and slides the elements queue.
 // It sends the slice of elements to the output channel if the window is not empty.
-func (sw *SlidingWindow[T]) dispatchWindow() {
+func (sw *SlidingWindow[T]) dispatchWindow(tick time.Time) {
 	sw.Lock()
 	// build a window of elements
 	var windowBottomIndex int
-	now := util.NowNano()
+	now := tick.UnixNano()
 	windowUpperIndex := sw.queue.Len()
 	slideUpperIndex := windowUpperIndex
 	slideUpperTime := now - sw.windowSize.Nanoseconds() + sw.slidingInterval.Nanoseconds()

flow/sliding_window_test.go

@@ -7,7 +7,6 @@ import (
 
 	ext "github.com/reugn/go-streams/extension"
 	"github.com/reugn/go-streams/flow"
-	"github.com/reugn/go-streams/util"
 )
 
 func TestSlidingWindow(t *testing.T) {
@@ -74,15 +73,15 @@ func TestSlidingWindowWithExtractor(t *testing.T) {
 
 	sink := ext.NewChanSink(out)
 
-	now := util.NowNano()
+	now := time.Now()
 	inputValues := []element{
-		{"a", now + 2*int64(time.Millisecond)},
-		{"b", now + 17*int64(time.Millisecond)},
-		{"c", now + 29*int64(time.Millisecond)},
-		{"d", now + 35*int64(time.Millisecond)},
-		{"e", now + 77*int64(time.Millisecond)},
-		{"f", now + 93*int64(time.Millisecond)},
-		{"g", now + 120*int64(time.Millisecond)},
+		{"a", now.Add(2 * time.Millisecond).UnixNano()},
+		{"b", now.Add(17 * time.Millisecond).UnixNano()},
+		{"c", now.Add(29 * time.Millisecond).UnixNano()},
+		{"d", now.Add(35 * time.Millisecond).UnixNano()},
+		{"e", now.Add(77 * time.Millisecond).UnixNano()},
+		{"f", now.Add(93 * time.Millisecond).UnixNano()},
+		{"g", now.Add(120 * time.Millisecond).UnixNano()},
 	}
 	go ingestSlice(inputValues, in)
 	go closeDeferred(in, 250*time.Millisecond)

util/util.go

@@ -2,7 +2,6 @@ package util
 
 import (
 	"hash/fnv"
-	"time"
 )
 
 // Check panics if the given error is not nil.
@@ -12,11 +11,6 @@ func Check(e error) {
 	}
 }
 
-// NowNano returns UnixNano in UTC.
-func NowNano() int64 {
-	return time.Now().UTC().UnixNano()
-}
-
 // HashCode returns a uint32 hash for the given byte array.
 func HashCode(b []byte) uint32 {
 	h := fnv.New32a()