[exporter][chore] Exporter queue batcher flushes current batch on shu…

…tdown (open-telemetry#11666)

#### Description

This PR changes exporter queue batcher to flush the current batch on
shutdown.

#### Link to tracking issue

open-telemetry#10368
open-telemetry#8122

exporter/internal/queue/batcher.go

@@ -94,9 +94,3 @@ func (qb *BaseBatcher) flushAsync(batchToFlush batch) {
 		qb.workerPool <- true
 	}()
 }
-
-// Shutdown ensures that queue and all Batcher are stopped.
-func (qb *BaseBatcher) Shutdown(_ context.Context) error {
-	qb.stopWG.Wait()
-	return nil
-}

exporter/internal/queue/default_batcher.go

@@ -124,18 +124,7 @@ func (qb *DefaultBatcher) startTimeBasedFlushingGoroutine() {
 			case <-qb.shutdownCh:
 				return
 			case <-qb.timer.C:
-				qb.currentBatchMu.Lock()
-				if qb.currentBatch == nil || qb.currentBatch.req == nil {
-					qb.currentBatchMu.Unlock()
-					continue
-				}
-				batchToFlush := *qb.currentBatch
-				qb.currentBatch = nil
-				qb.currentBatchMu.Unlock()
-
-				// flushAsync() blocks until successfully started a goroutine for flushing.
-				qb.flushAsync(batchToFlush)
-				qb.resetTimer()
+				qb.flushCurrentBatchIfNecessary()
 			}
 		}
 	}()
@@ -155,6 +144,28 @@ func (qb *DefaultBatcher) Start(_ context.Context, _ component.Host) error {
 
 	qb.startReadingFlushingGoroutine()
 	qb.startTimeBasedFlushingGoroutine()
+	return nil
+}
+
+// flushCurrentBatchIfNecessary sends out the current request batch if it is not nil
+func (qb *DefaultBatcher) flushCurrentBatchIfNecessary() {
+	qb.currentBatchMu.Lock()
+	if qb.currentBatch == nil || qb.currentBatch.req == nil {
+		qb.currentBatchMu.Unlock()
+		return
+	}
+	batchToFlush := *qb.currentBatch
+	qb.currentBatch = nil
+	qb.currentBatchMu.Unlock()
+
+	// flushAsync() blocks until successfully started a goroutine for flushing.
+	qb.flushAsync(batchToFlush)
+	qb.resetTimer()
+}
 
+// Shutdown ensures that queue and all Batcher are stopped.
+func (qb *DefaultBatcher) Shutdown(_ context.Context) error {
+	qb.flushCurrentBatchIfNecessary()
+	qb.stopWG.Wait()
 	return nil
 }

exporter/internal/queue/default_batcher_test.go

@@ -277,3 +277,40 @@ func TestDefaultBatcher_Split_TimeoutDisabled(t *testing.T) {
 		})
 	}
 }
+
+func TestDefaultBatcher_Shutdown(t *testing.T) {
+	batchCfg := exporterbatcher.NewDefaultConfig()
+	batchCfg.MinSizeItems = 10
+	batchCfg.FlushTimeout = 100 * time.Second
+
+	q := NewBoundedMemoryQueue[internal.Request](
+		MemoryQueueSettings[internal.Request]{
+			Sizer:    &RequestSizer[internal.Request]{},
+			Capacity: 10,
+		})
+
+	ba, err := NewBatcher(batchCfg, q,
+		func(ctx context.Context, req internal.Request) error { return req.Export(ctx) },
+		2)
+	require.NoError(t, err)
+
+	require.NoError(t, q.Start(context.Background(), componenttest.NewNopHost()))
+	require.NoError(t, ba.Start(context.Background(), componenttest.NewNopHost()))
+
+	sink := newFakeRequestSink()
+
+	require.NoError(t, q.Offer(context.Background(), &fakeRequest{items: 1, sink: sink}))
+	require.NoError(t, q.Offer(context.Background(), &fakeRequest{items: 2, sink: sink}))
+
+	// Give the batcher some time to read from queue
+	time.Sleep(100 * time.Millisecond)
+
+	assert.Equal(t, int64(0), sink.requestsCount.Load())
+	assert.Equal(t, int64(0), sink.itemsCount.Load())
+
+	require.NoError(t, q.Shutdown(context.Background()))
+	require.NoError(t, ba.Shutdown(context.Background()))
+
+	assert.Equal(t, int64(1), sink.requestsCount.Load())
+	assert.Equal(t, int64(3), sink.itemsCount.Load())
+}

exporter/internal/queue/disabled_batcher.go

@@ -38,3 +38,9 @@ func (qb *DisabledBatcher) Start(_ context.Context, _ component.Host) error {
 	}()
 	return nil
 }
+
+// Shutdown ensures that queue and all Batcher are stopped.
+func (qb *DisabledBatcher) Shutdown(_ context.Context) error {
+	qb.stopWG.Wait()
+	return nil
+}