Move the consumer's channel send slightly

Prep for unblocking consumers that are not being drained

consumer.go

@@ -401,8 +401,15 @@ func (child *partitionConsumer) HighWaterMarkOffset() int64 {
 }
 
 func (child *partitionConsumer) responseFeeder() {
+	var msgs []*ConsumerMessage
+
 	for response := range child.feeder {
-		child.responseResult = child.handleResponse(response)
+		msgs, child.responseResult = child.parseResponse(response)
+
+		for _, msg := range msgs {
+			child.messages <- msg
+		}
+
 		child.broker.acks.Done()
 	}
 
@@ -410,14 +417,14 @@ func (child *partitionConsumer) responseFeeder() {
 	close(child.errors)
 }
 
-func (child *partitionConsumer) handleResponse(response *FetchResponse) error {
+func (child *partitionConsumer) parseResponse(response *FetchResponse) ([]*ConsumerMessage, error) {
 	block := response.GetBlock(child.topic, child.partition)
 	if block == nil {
-		return ErrIncompleteResponse
+		return nil, ErrIncompleteResponse
 	}
 
 	if block.Err != ErrNoError {
-		return block.Err
+		return nil, block.Err
 	}
 
 	if len(block.MsgSet.Messages) == 0 {
@@ -436,7 +443,7 @@ func (child *partitionConsumer) handleResponse(response *FetchResponse) error {
 			}
 		}
 
-		return nil
+		return nil, nil
 	}
 
 	// we got messages, reset our fetch size in case it was increased for a previous request
@@ -444,8 +451,8 @@ func (child *partitionConsumer) handleResponse(response *FetchResponse) error {
 	atomic.StoreInt64(&child.highWaterMarkOffset, block.HighWaterMarkOffset)
 
 	incomplete := false
-	atLeastOne := false
 	prelude := true
+	var messages []*ConsumerMessage
 	for _, msgBlock := range block.MsgSet.Messages {
 
 		for _, msg := range msgBlock.Messages() {
@@ -455,14 +462,13 @@ func (child *partitionConsumer) handleResponse(response *FetchResponse) error {
 			prelude = false
 
 			if msg.Offset >= child.offset {
-				atLeastOne = true
-				child.messages <- &ConsumerMessage{
+				messages = append(messages, &ConsumerMessage{
 					Topic:     child.topic,
 					Partition: child.partition,
 					Key:       msg.Msg.Key,
 					Value:     msg.Msg.Value,
 					Offset:    msg.Offset,
-				}
+				})
 				child.offset = msg.Offset + 1
 			} else {
 				incomplete = true
@@ -471,10 +477,10 @@ func (child *partitionConsumer) handleResponse(response *FetchResponse) error {
 
 	}
 
-	if incomplete || !atLeastOne {
-		return ErrIncompleteResponse
+	if incomplete || len(messages) == 0 {
+		return nil, ErrIncompleteResponse
 	}
-	return nil
+	return messages, nil
 }
 
 // brokerConsumer