[chore] - address comments (#2920)

* address comments

* fix test

* address comments

* update comments

* fix tests

* lint

* do the thing

pkg/channelmetrics/observablechan.go

@@ -23,9 +23,8 @@ type MetricsCollector interface {
 // It supports any type of channel and records metrics using a provided
 // MetricsCollector implementation.
 type ObservableChan[T any] struct {
-	ch        chan T
-	metrics   MetricsCollector
-	bufferCap int
+	ch      chan T
+	metrics MetricsCollector
 }
 
 // NewObservableChan creates a new ObservableChan wrapping the provided channel.
@@ -35,11 +34,13 @@ type ObservableChan[T any] struct {
 // the metric names.
 func NewObservableChan[T any](ch chan T, metrics MetricsCollector) *ObservableChan[T] {
 	oChan := &ObservableChan[T]{
-		ch:        ch,
-		metrics:   metrics,
-		bufferCap: cap(ch),
+		ch:      ch,
+		metrics: metrics,
 	}
-	oChan.RecordChannelCapacity() // Record capacity immediately
+	oChan.RecordChannelCapacity()
+	// Record the current length of the channel.
+	// Note: The channel is likely empty, but it may contain items if it was pre-existing.
+	oChan.RecordChannelLen()
 	return oChan
 }
 
@@ -51,34 +52,42 @@ func (oc *ObservableChan[T]) Close() {
 
 // Send sends an item into the channel and records the duration taken to do so.
 // It also updates the current size of the channel buffer.
-func (oc *ObservableChan[T]) Send(ctx context.Context, item T) {
-	startTime := time.Now()
-	defer func() {
-		oc.metrics.RecordProduceDuration(time.Since(startTime))
+// This method blocks until the item is sent.
+func (oc *ObservableChan[T]) Send(item T) { _ = oc.SendCtx(context.Background(), item) }
+
+// SendCtx sends an item into the channel with context and records the duration taken to do so.
+// It also updates the current size of the channel buffer and supports context cancellation.
+func (oc *ObservableChan[T]) SendCtx(ctx context.Context, item T) error {
+	defer func(start time.Time) {
+		oc.metrics.RecordProduceDuration(time.Since(start))
 		oc.RecordChannelLen()
-	}()
-	if err := common.CancellableWrite(ctx, oc.ch, item); err != nil {
-		ctx.Logger().Error(err, "failed to write item to observable channel")
-	}
+	}(time.Now())
+
+	return common.CancellableWrite(ctx, oc.ch, item)
 }
 
 // Recv receives an item from the channel and records the duration taken to do so.
 // It also updates the current size of the channel buffer.
-func (oc *ObservableChan[T]) Recv(_ context.Context) T {
-	startTime := time.Now()
-	defer func() {
-		oc.metrics.RecordConsumeDuration(time.Since(startTime))
+// This method blocks until an item is available.
+func (oc *ObservableChan[T]) Recv() T {
+	v, _ := oc.RecvCtx(context.Background())
+	return v
+}
+
+// RecvCtx receives an item from the channel with context and records the duration taken to do so.
+// It also updates the current size of the channel buffer and supports context cancellation.
+// If an error occurs, it logs the error.
+func (oc *ObservableChan[T]) RecvCtx(ctx context.Context) (T, error) {
+	defer func(start time.Time) {
+		oc.metrics.RecordConsumeDuration(time.Since(start))
 		oc.RecordChannelLen()
-	}()
-	return <-oc.ch
+	}(time.Now())
+
+	return common.CancellableRecv(ctx, oc.ch)
 }
 
 // RecordChannelCapacity records the capacity of the channel buffer.
-func (oc *ObservableChan[T]) RecordChannelCapacity() {
-	oc.metrics.RecordChannelCap(oc.bufferCap)
-}
+func (oc *ObservableChan[T]) RecordChannelCapacity() { oc.metrics.RecordChannelCap(cap(oc.ch)) }
 
 // RecordChannelLen records the current size of the channel buffer.
-func (oc *ObservableChan[T]) RecordChannelLen() {
-	oc.metrics.RecordChannelLen(len(oc.ch))
-}
+func (oc *ObservableChan[T]) RecordChannelLen() { oc.metrics.RecordChannelLen(len(oc.ch)) }

pkg/channelmetrics/observablechan_test.go

@@ -27,14 +27,15 @@ func TestObservableChanSend(t *testing.T) {
 	bufferCap := 10
 
 	mockMetrics.On("RecordProduceDuration", mock.Anything).Once()
-	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Once()
+	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Twice()
 	mockMetrics.On("RecordChannelCap", bufferCap).Once()
 
 	ch := make(chan int, bufferCap)
 	oc := NewObservableChan(ch, mockMetrics)
 	assert.Equal(t, bufferCap, cap(oc.ch))
 
-	oc.Send(context.Background(), 1)
+	err := oc.SendCtx(context.Background(), 1)
+	assert.NoError(t, err)
 
 	mockMetrics.AssertExpectations(t)
 }
@@ -47,20 +48,22 @@ func TestObservableChanRecv(t *testing.T) {
 
 	mockMetrics.On("RecordConsumeDuration", mock.Anything).Once() // For the send
 	mockMetrics.On("RecordProduceDuration", mock.Anything).Once()
-	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Twice() // For the send and recv
+	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Times(3) // For the send and recv
 	mockMetrics.On("RecordChannelCap", bufferCap).Once()
 
 	ch := make(chan int, bufferCap)
 	oc := NewObservableChan(ch, mockMetrics)
 	assert.Equal(t, bufferCap, cap(oc.ch))
 
 	go func() {
-		oc.Send(context.Background(), 1)
+		err := oc.SendCtx(context.Background(), 1)
+		assert.NoError(t, err)
 	}()
 
 	time.Sleep(100 * time.Millisecond) // Ensure Send happens before Recv
 
-	oc.Recv(context.Background())
+	_, err := oc.RecvCtx(context.Background())
+	assert.NoError(t, err)
 
 	mockMetrics.AssertExpectations(t)
 }
@@ -72,6 +75,7 @@ func TestObservableChanRecordChannelCapacity(t *testing.T) {
 	bufferCap := 10
 
 	mockMetrics.On("RecordChannelCap", bufferCap).Twice()
+	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Once()
 
 	ch := make(chan int, bufferCap)
 	oc := NewObservableChan(ch, mockMetrics)
@@ -87,7 +91,7 @@ func TestObservableChanRecordChannelLen(t *testing.T) {
 	mockMetrics := new(MockMetricsCollector)
 	bufferCap := 10
 
-	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Once()
+	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Twice()
 	mockMetrics.On("RecordChannelCap", bufferCap).Once()
 
 	ch := make(chan int, bufferCap)
@@ -105,7 +109,7 @@ func TestObservableChan_Close(t *testing.T) {
 	bufferCap := 1
 
 	mockMetrics.On("RecordChannelCap", bufferCap).Once()
-	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Once()
+	mockMetrics.On("RecordChannelLen", mock.AnythingOfType("int")).Twice()
 
 	ch := make(chan int, bufferCap)
 	oc := NewObservableChan(ch, mockMetrics)

pkg/common/context.go

@@ -27,3 +27,22 @@ func CancellableWrite[T any](ctx context.Context, ch chan<- T, item T) error {
 		}
 	}
 }
+
+// CancellableRecv blocks on receiving an item from the channel but can be
+// cancelled by the context. If both the context is cancelled and the channel
+// read would succeed, either operation will be performed randomly.
+func CancellableRecv[T any](ctx context.Context, ch <-chan T) (T, error) {
+	var zero T // zero value of type T
+
+	select {
+	case <-ctx.Done(): // priority to context cancellation
+		return zero, ctx.Err()
+	default:
+		select {
+		case <-ctx.Done():
+			return zero, ctx.Err()
+		case item := <-ch:
+			return item, nil
+		}
+	}
+}