[chore] Unify persistentQueue fields into QueueMetadata (open-telemetry#13140)

Embed QueueMetadata directly into persistentQueue, replacing the
scattered metadata fields.

1. Add QueueMetadata as a member of persistentQueue.
2. Delete redundant fields (queueSize, readIdx, writeIdx, …).

Relates to open-telemetry#13126

Author: malus2077

exporter/exporterhelper/internal/queuebatch/persistent_queue.go

@@ -98,11 +98,8 @@ type persistentQueue[T any] struct {
 	mu                       sync.Mutex
 	hasMoreElements          *sync.Cond
 	hasMoreSpace             *cond
-	readIndex                uint64
-	writeIndex               uint64
-	currentlyDispatchedItems []uint64
-	queueSize                int64
-	refClient                int64
+	metadata                 *persistentqueue.QueueMetadata
+        refClient                int64
 	stopped                  bool
 
 	sizerTypeMismatch       atomic.Bool
@@ -137,7 +134,7 @@ func (pq *persistentQueue[T]) Start(ctx context.Context, host component.Host) er
 func (pq *persistentQueue[T]) Size() int64 {
 	pq.mu.Lock()
 	defer pq.mu.Unlock()
-	return pq.queueSize
+	return pq.metadata.QueueSize
 }
 
 func (pq *persistentQueue[T]) Capacity() int64 {
@@ -167,11 +164,11 @@ func (pq *persistentQueue[T]) initPersistentContiguousStorage(ctx context.Contex
 
 	err := pq.client.Batch(ctx, riOp, wiOp)
 	if err == nil {
-		pq.readIndex, err = bytesToItemIndex(riOp.Value)
+		pq.metadata.ReadIndex, err = bytesToItemIndex(riOp.Value)
 	}
 
 	if err == nil {
-		pq.writeIndex, err = bytesToItemIndex(wiOp.Value)
+		pq.metadata.WriteIndex, err = bytesToItemIndex(wiOp.Value)
 	}
 
 	if err != nil {
@@ -180,11 +177,11 @@ func (pq *persistentQueue[T]) initPersistentContiguousStorage(ctx context.Contex
 		} else {
 			pq.logger.Error("Failed getting read/write index, starting with new ones", zap.Error(err))
 		}
-		pq.readIndex = 0
-		pq.writeIndex = 0
+		pq.metadata.ReadIndex = 0
+		pq.metadata.WriteIndex = 0
 	}
 
-	queueSize := pq.writeIndex - pq.readIndex
+	queueSize := pq.metadata.WriteIndex - pq.metadata.ReadIndex
 
 	// If the queue is sized by the number of requests, no need to read the queue size from storage.
 	if queueSize > 0 && !pq.isRequestSized {
@@ -359,7 +356,7 @@ func (pq *persistentQueue[T]) Offer(ctx context.Context, req T) error {
 // putInternal is the internal version that requires caller to hold the mutex lock.
 func (pq *persistentQueue[T]) putInternal(ctx context.Context, req T) error {
 	reqSize := pq.set.sizer.Sizeof(req)
-	for pq.queueSize+reqSize > pq.set.capacity {
+	for pq.metadata.QueueSize+reqSize > pq.set.capacity {
 		if !pq.set.blockOnOverflow {
 			return ErrQueueIsFull
 		}
@@ -418,11 +415,11 @@ func (pq *persistentQueue[T]) Read(ctx context.Context) (context.Context, T, Don
 		}
 
 		// Read until either a successful retrieved element or no more elements in the storage.
-		for pq.readIndex != pq.writeIndex {
+		for pq.metadata.ReadIndex != pq.metadata.WriteIndex {
 			index, req, consumed := pq.getNextItem(ctx)
 			// Ensure the used size and the channel size are in sync.
-			if pq.readIndex == pq.writeIndex {
-				pq.queueSize = 0
+			if pq.metadata.ReadIndex == pq.metadata.WriteIndex {
+				pq.metadata.QueueSize = 0
 				pq.hasMoreSpace.Signal()
 			}
 			if consumed {
@@ -442,7 +439,7 @@ func (pq *persistentQueue[T]) Read(ctx context.Context) (context.Context, T, Don
 // finished, the index should be called with onDone to clean up the storage. If no new item is available,
 // returns false.
 func (pq *persistentQueue[T]) getNextItem(ctx context.Context) (uint64, T, bool) {
-	index := pq.readIndex
+	index := pq.metadata.ReadIndex
 	// Increase here, so even if errors happen below, it always iterates
 	pq.readIndex++
 	pq.currentlyDispatchedItems = append(pq.currentlyDispatchedItems, index)
@@ -496,12 +493,12 @@ func (pq *persistentQueue[T]) onDone(index uint64, elSize int64, consumeErr erro
 		pq.mu.Unlock()
 	}()
 
-	pq.queueSize -= elSize
+	pq.metadata.QueueSize -= elSize
 	// The size might be not in sync with the queue in case it's restored from the disk
 	// because we don't flush the current queue size on the disk on every read/write.
 	// In that case we need to make sure it doesn't go below 0.
-	if pq.queueSize < 0 {
-		pq.queueSize = 0
+	if pq.metadata.QueueSize < 0 {
+		pq.metadata.QueueSize = 0
 	}
 	pq.hasMoreSpace.Signal()
 
@@ -593,11 +590,11 @@ func (pq *persistentQueue[T]) retrieveAndEnqueueNotDispatchedReqs(ctx context.Co
 
 // itemDispatchingFinish removes the item from the list of currently dispatched items and deletes it from the persistent queue
 func (pq *persistentQueue[T]) itemDispatchingFinish(ctx context.Context, index uint64) error {
-	lenCDI := len(pq.currentlyDispatchedItems)
+	lenCDI := len(pq.metadata.CurrentlyDispatchedItems)
 	for i := 0; i < lenCDI; i++ {
-		if pq.currentlyDispatchedItems[i] == index {
-			pq.currentlyDispatchedItems[i] = pq.currentlyDispatchedItems[lenCDI-1]
-			pq.currentlyDispatchedItems = pq.currentlyDispatchedItems[:lenCDI-1]
+		if pq.metadata.CurrentlyDispatchedItems[i] == index {
+			pq.metadata.CurrentlyDispatchedItems[i] = pq.metadata.CurrentlyDispatchedItems[lenCDI-1]
+			pq.metadata.CurrentlyDispatchedItems = pq.metadata.CurrentlyDispatchedItems[:lenCDI-1]
 			break
 		}
 	}

exporter/exporterhelper/internal/queuebatch/persistent_queue_test.go

@@ -679,10 +679,10 @@ func TestPersistentQueue_CurrentlyProcessedItems(t *testing.T) {
 	requireCurrentlyDispatchedItemsEqual(t, newPs, []uint64{})
 	assert.Equal(t, int64(0), newPs.Size())
 	// The writeIndex should be now set accordingly
-	require.EqualValues(t, 6, newPs.writeIndex)
+	require.EqualValues(t, 6, newPs.metadata.WriteIndex)
 
 	// There should be no items left in the storage
-	for i := uint64(0); i < newPs.writeIndex; i++ {
+	for i := uint64(0); i < newPs.metadata.WriteIndex; i++ {
 		bb, err := newPs.client.Get(context.Background(), getItemKey(i))
 		require.NoError(t, err)
 		require.Nil(t, bb)
@@ -1264,5 +1264,5 @@ func TestPersistentQueue_SizerLegacyFormatMigration(t *testing.T) {
 func requireCurrentlyDispatchedItemsEqual(t *testing.T, pq *persistentQueue[uint64], compare []uint64) {
 	pq.mu.Lock()
 	defer pq.mu.Unlock()
-	assert.ElementsMatch(t, compare, pq.currentlyDispatchedItems)
+	assert.ElementsMatch(t, compare, pq.metadata.CurrentlyDispatchedItems)
 }