Add capability for memory and persistent queue to block when add items (#12074)

This functionality is not yet exposed to the user because there is no
config available. One option to consider is to add a "blocking" bool in
the queue config.

#### Link to tracking issue

#8122
#10368

Signed-off-by: Bogdan Drutu <[email protected]>

Author: bogdandrutu

.chloggen/add-blocking.yaml

@@ -0,0 +1,25 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. otlpreceiver)
+component: exporterhelper
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add capability for memory and persistent queue to block when add items
+
+# One or more tracking issues or pull requests related to the change
+issues: [12074]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: [api]

exporter/exporterqueue/bounded_memory_queue.go

@@ -23,17 +23,18 @@ type boundedMemoryQueue[T any] struct {
 type memoryQueueSettings[T any] struct {
 	sizer    sizer[T]
 	capacity int64
+	blocking bool
 }
 
 // newBoundedMemoryQueue constructs the new queue of specified capacity, and with an optional
 // callback for dropped items (e.g. useful to emit metrics).
 func newBoundedMemoryQueue[T any](set memoryQueueSettings[T]) Queue[T] {
 	return &boundedMemoryQueue[T]{
-		sizedQueue: newSizedQueue[T](set.capacity, set.sizer),
+		sizedQueue: newSizedQueue[T](set.capacity, set.sizer, set.blocking),
 	}
 }
 
-func (q *boundedMemoryQueue[T]) Read(_ context.Context) (uint64, context.Context, T, bool) {
+func (q *boundedMemoryQueue[T]) Read(context.Context) (uint64, context.Context, T, bool) {
 	ctx, req, ok := q.sizedQueue.pop()
 	return 0, ctx, req, ok
 }

exporter/exporterqueue/bounded_memory_queue_test.go

@@ -16,8 +16,6 @@ import (
 	"github.com/stretchr/testify/require"
 
 	"go.opentelemetry.io/collector/component/componenttest"
-	"go.opentelemetry.io/collector/pdata/ptrace"
-	"go.opentelemetry.io/collector/pdata/testdata"
 )
 
 // In this test we run a queue with capacity 1 and a single consumer.
@@ -102,11 +100,11 @@ func TestShutdownWhileNotEmpty(t *testing.T) {
 func TestQueueUsage(t *testing.T) {
 	tests := []struct {
 		name  string
-		sizer sizer[ptrace.Traces]
+		sizer sizer[uint64]
 	}{
 		{
 			name:  "requests_based",
-			sizer: &requestSizer[ptrace.Traces]{},
+			sizer: &requestSizer[uint64]{},
 		},
 		{
 			name:  "items_based",
@@ -115,16 +113,15 @@ func TestQueueUsage(t *testing.T) {
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			q := newBoundedMemoryQueue[ptrace.Traces](memoryQueueSettings[ptrace.Traces]{sizer: tt.sizer, capacity: int64(100)})
+			q := newBoundedMemoryQueue[uint64](memoryQueueSettings[uint64]{sizer: tt.sizer, capacity: int64(100)})
 			consumed := &atomic.Int64{}
 			require.NoError(t, q.Start(context.Background(), componenttest.NewNopHost()))
-			ac := newAsyncConsumer(q, 1, func(context.Context, ptrace.Traces) error {
+			ac := newAsyncConsumer(q, 1, func(context.Context, uint64) error {
 				consumed.Add(1)
 				return nil
 			})
-			td := testdata.GenerateTraces(10)
 			for j := 0; j < 10; j++ {
-				require.NoError(t, q.Offer(context.Background(), td))
+				require.NoError(t, q.Offer(context.Background(), uint64(10)))
 			}
 			assert.NoError(t, q.Shutdown(context.Background()))
 			assert.NoError(t, ac.Shutdown(context.Background()))
@@ -133,6 +130,47 @@ func TestQueueUsage(t *testing.T) {
 	}
 }
 
+func TestBlockingQueueUsage(t *testing.T) {
+	tests := []struct {
+		name  string
+		sizer sizer[uint64]
+	}{
+		{
+			name:  "requests_based",
+			sizer: &requestSizer[uint64]{},
+		},
+		{
+			name:  "items_based",
+			sizer: &itemsSizer{},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			q := newBoundedMemoryQueue[uint64](memoryQueueSettings[uint64]{sizer: tt.sizer, capacity: int64(100), blocking: true})
+			consumed := &atomic.Int64{}
+			require.NoError(t, q.Start(context.Background(), componenttest.NewNopHost()))
+			ac := newAsyncConsumer(q, 10, func(context.Context, uint64) error {
+				consumed.Add(1)
+				return nil
+			})
+			wg := &sync.WaitGroup{}
+			for i := 0; i < 10; i++ {
+				wg.Add(1)
+				go func() {
+					defer wg.Done()
+					for j := 0; j < 100_000; j++ {
+						assert.NoError(t, q.Offer(context.Background(), uint64(10)))
+					}
+				}()
+			}
+			wg.Wait()
+			assert.NoError(t, q.Shutdown(context.Background()))
+			assert.NoError(t, ac.Shutdown(context.Background()))
+			assert.Equal(t, int64(1_000_000), consumed.Load())
+		})
+	}
+}
+
 func TestZeroSizeNoConsumers(t *testing.T) {
 	q := newBoundedMemoryQueue[string](memoryQueueSettings[string]{sizer: &requestSizer[string]{}, capacity: 0})
 
@@ -149,8 +187,7 @@ func consume[T any](q Queue[T], consumeFunc func(context.Context, T) error) bool
 	if !ok {
 		return false
 	}
-	consumeErr := consumeFunc(ctx, req)
-	q.OnProcessingFinished(index, consumeErr)
+	q.OnProcessingFinished(index, consumeFunc(ctx, req))
 	return true
 }
 
@@ -170,8 +207,7 @@ func newAsyncConsumer[T any](q Queue[T], numConsumers int, consumeFunc func(cont
 				if !ok {
 					return
 				}
-				consumeErr := consumeFunc(ctx, req)
-				q.OnProcessingFinished(index, consumeErr)
+				q.OnProcessingFinished(index, consumeFunc(ctx, req))
 			}
 		}()
 	}
@@ -187,11 +223,11 @@ func (qc *asyncConsumer) Shutdown(_ context.Context) error {
 func BenchmarkOffer(b *testing.B) {
 	tests := []struct {
 		name  string
-		sizer sizer[ptrace.Traces]
+		sizer sizer[uint64]
 	}{
 		{
 			name:  "requests_based",
-			sizer: &requestSizer[ptrace.Traces]{},
+			sizer: &requestSizer[uint64]{},
 		},
 		{
 			name:  "items_based",
@@ -200,18 +236,17 @@ func BenchmarkOffer(b *testing.B) {
 	}
 	for _, tt := range tests {
 		b.Run(tt.name, func(b *testing.B) {
-			q := newBoundedMemoryQueue[ptrace.Traces](memoryQueueSettings[ptrace.Traces]{sizer: &requestSizer[ptrace.Traces]{}, capacity: int64(10 * b.N)})
+			q := newBoundedMemoryQueue[uint64](memoryQueueSettings[uint64]{sizer: &requestSizer[uint64]{}, capacity: int64(10 * b.N)})
 			consumed := &atomic.Int64{}
 			require.NoError(b, q.Start(context.Background(), componenttest.NewNopHost()))
-			ac := newAsyncConsumer(q, 1, func(context.Context, ptrace.Traces) error {
+			ac := newAsyncConsumer(q, 1, func(context.Context, uint64) error {
 				consumed.Add(1)
 				return nil
 			})
-			td := testdata.GenerateTraces(10)
 			b.ResetTimer()
 			b.ReportAllocs()
 			for j := 0; j < b.N; j++ {
-				require.NoError(b, q.Offer(context.Background(), td))
+				require.NoError(b, q.Offer(context.Background(), uint64(10)))
 			}
 			assert.NoError(b, q.Shutdown(context.Background()))
 			assert.NoError(b, ac.Shutdown(context.Background()))

exporter/exporterqueue/cond.go

@@ -0,0 +1,63 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package exporterqueue // import "go.opentelemetry.io/collector/exporter/exporterqueue"
+
+import (
+	"context"
+	"sync"
+)
+
+// cond is equivalent with sync.Cond, but context.Context aware.
+// Which means Wait() will return if context is done before any signal is received.
+// Also, it requires the caller to hold the c.L during all calls.
+type cond struct {
+	L       sync.Locker
+	ch      chan struct{}
+	waiting int64
+}
+
+func newCond(l sync.Locker) *cond {
+	return &cond{L: l, ch: make(chan struct{}, 1)}
+}
+
+// Signal wakes one goroutine waiting on c, if there is any.
+// It requires for the caller to hold c.L during the call.
+func (c *cond) Signal() {
+	if c.waiting == 0 {
+		return
+	}
+	c.waiting--
+	c.ch <- struct{}{}
+}
+
+// Broadcast wakes all goroutines waiting on c.
+// It requires for the caller to hold c.L during the call.
+func (c *cond) Broadcast() {
+	for ; c.waiting > 0; c.waiting-- {
+		c.ch <- struct{}{}
+	}
+}
+
+// Wait atomically unlocks c.L and suspends execution of the calling goroutine. After later resuming execution, Wait locks c.L before returning.
+func (c *cond) Wait(ctx context.Context) error {
+	c.waiting++
+	c.L.Unlock()
+	select {
+	case <-ctx.Done():
+		c.L.Lock()
+		if c.waiting == 0 {
+			// If waiting is 0, it means that there was a signal sent and nobody else waits for it.
+			// Consume it, so that we don't unblock other consumer unnecessary,
+			// or we don't block the producer because the channel buffer is full.
+			<-c.ch
+		} else {
+			// Decrease the number of waiting routines.
+			c.waiting--
+		}
+		return ctx.Err()
+	case <-c.ch:
+		c.L.Lock()
+		return nil
+	}
+}

exporter/exporterqueue/persistent_queue.go

@@ -11,7 +11,6 @@ import (
 	"strconv"
 	"sync"
 
-	"go.uber.org/multierr"
 	"go.uber.org/zap"
 
 	"go.opentelemetry.io/collector/component"
@@ -42,6 +41,7 @@ var (
 type persistentQueueSettings[T any] struct {
 	sizer       sizer[T]
 	capacity    int64
+	blocking    bool
 	signal      pipeline.Signal
 	storageID   component.ID
 	marshaler   Marshaler[T]
@@ -81,7 +81,8 @@ type persistentQueue[T any] struct {
 
 	// mu guards everything declared below.
 	mu                       sync.Mutex
-	hasElements              *sync.Cond
+	hasMoreElements          *sync.Cond
+	hasMoreSpace             *cond
 	readIndex                uint64
 	writeIndex               uint64
 	currentlyDispatchedItems []uint64
@@ -98,7 +99,8 @@ func newPersistentQueue[T any](set persistentQueueSettings[T]) Queue[T] {
 		logger:         set.set.Logger,
 		isRequestSized: isRequestSized,
 	}
-	pq.hasElements = sync.NewCond(&pq.mu)
+	pq.hasMoreElements = sync.NewCond(&pq.mu)
+	pq.hasMoreSpace = newCond(&pq.mu)
 	return pq
 }
 
@@ -194,8 +196,8 @@ func (pq *persistentQueue[T]) Shutdown(ctx context.Context) error {
 	backupErr := pq.backupQueueSize(ctx)
 	// Mark this queue as stopped, so consumer don't start any more work.
 	pq.stopped = true
-	pq.hasElements.Broadcast()
-	return multierr.Combine(backupErr, pq.unrefClient(ctx))
+	pq.hasMoreElements.Broadcast()
+	return errors.Join(backupErr, pq.unrefClient(ctx))
 }
 
 // backupQueueSize writes the current queue size to storage. The value is used to recover the queue size
@@ -233,8 +235,13 @@ 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)
-	if pq.queueSize+reqSize > pq.set.capacity {
-		return ErrQueueIsFull
+	for pq.queueSize+reqSize > pq.set.capacity {
+		if !pq.set.blocking {
+			return ErrQueueIsFull
+		}
+		if err := pq.hasMoreSpace.Wait(ctx); err != nil {
+			return err
+		}
 	}
 
 	reqBuf, err := pq.set.marshaler(req)
@@ -253,7 +260,7 @@ func (pq *persistentQueue[T]) putInternal(ctx context.Context, req T) error {
 
 	pq.writeIndex++
 	pq.queueSize += reqSize
-	pq.hasElements.Signal()
+	pq.hasMoreElements.Signal()
 
 	// Back up the queue size to storage every 10 writes. The stored value is used to recover the queue size
 	// in case if the collector is killed. The recovered queue size is allowed to be inaccurate.
@@ -269,32 +276,38 @@ func (pq *persistentQueue[T]) putInternal(ctx context.Context, req T) error {
 func (pq *persistentQueue[T]) Read(ctx context.Context) (uint64, context.Context, T, bool) {
 	pq.mu.Lock()
 	defer pq.mu.Unlock()
+
 	for {
 		if pq.stopped {
 			var req T
 			return 0, context.Background(), req, false
 		}
 
-		// If queue is empty, wait until more elements and restart.
-		if pq.readIndex == pq.writeIndex {
-			pq.hasElements.Wait()
-			continue
-		}
-
-		index, req, consumed := pq.getNextItem(ctx)
-		if consumed {
-			pq.queueSize -= pq.set.sizer.Sizeof(req)
-			// 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 {
+		// Read until either a successful retrieved element or no more elements in the storage.
+		for pq.readIndex != pq.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
+				pq.hasMoreSpace.Signal()
+			}
+			if consumed {
+				pq.queueSize -= pq.set.sizer.Sizeof(req)
+				// 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
+				}
+				pq.hasMoreSpace.Signal()
+
+				return index, context.Background(), req, true
 			}
-
-			return index, context.Background(), req, true
 		}
 
-		// If we did not consume any element retry from the beginning.
+		// TODO: Need to change the Queue interface to return an error to allow distinguish between shutdown and context canceled.
+		//  Until then use the sync.Cond.
+		pq.hasMoreElements.Wait()
 	}
 }
 
@@ -363,11 +376,6 @@ func (pq *persistentQueue[T]) OnProcessingFinished(index uint64, consumeErr erro
 			pq.logger.Error("Error writing queue size to storage", zap.Error(qsErr))
 		}
 	}
-
-	// Ensure the used size and the channel size are in sync.
-	if pq.readIndex == pq.writeIndex {
-		pq.queueSize = 0
-	}
 }
 
 // retrieveAndEnqueueNotDispatchedReqs gets the items for which sending was not finished, cleans the storage