Patch sarama_kafka rebalance fix (#818)

* Patch sarama_kafka rebalance fix

Issue: #817
Issue Explanation: IBM/sarama#2118
Fix reference: https://github.com/Shopify/sarama/blob/5e2c2ef0e429f895c86152189f625bfdad7d3452/examples/consumergroup/main.go#L177

Signed-off-by: nbajaj90 <nbajaj90@gmail.com>

* Adding comment as per code review comment

Signed-off-by: nbajaj90 <nbajaj90@gmail.com>

* Fixing typo

Signed-off-by: nbajaj90 <nbajaj90@gmail.com>

* Incorporated review comment to move comment

Signed-off-by: nbajaj90 <nbajaj90@gmail.com>

Signed-off-by: nbajaj90 <nbajaj90@gmail.com>

protocol/kafka_sarama/v2/receiver.go

@@ -52,20 +52,40 @@ func (r *Receiver) Close(context.Context) error {
 	return nil
 }
 
+// ConsumeClaim must start a consumer loop of ConsumerGroupClaim's Messages().
+// Also the method should return when `session.Context()` is done.
+// Refer - https://github.com/Shopify/sarama/blob/5e2c2ef0e429f895c86152189f625bfdad7d3452/examples/consumergroup/main.go#L177
 func (r *Receiver) ConsumeClaim(session sarama.ConsumerGroupSession, claim sarama.ConsumerGroupClaim) error {
-	for message := range claim.Messages() {
-		msg := message
-		m := NewMessageFromConsumerMessage(msg)
-
-		r.incoming <- msgErr{
-			msg: binding.WithFinish(m, func(err error) {
-				if protocol.IsACK(err) {
-					session.MarkMessage(msg, "")
-				}
-			}),
+	// NOTE:
+	// Do not move the code below to a goroutine.
+	// The `ConsumeClaim` itself is called within a goroutine, see:
+	// https://github.com/Shopify/sarama/blob/main/consumer_group.go#L27-L29
+	for {
+		select {
+		case msg := <-claim.Messages():
+			m := NewMessageFromConsumerMessage(msg)
+
+			r.incoming <- msgErr{
+				msg: binding.WithFinish(m, func(err error) {
+					if protocol.IsACK(err) {
+						session.MarkMessage(msg, "")
+					}
+				}),
+			}
+
+		// Should return when `session.Context()` is done.
+		// If not, will raise `ErrRebalanceInProgress` or `read tcp <ip>:<port>: i/o timeout` when kafka rebalance. see:
+		// https://github.com/Shopify/sarama/issues/1192
+		// https://github.com/Shopify/sarama/issues/2118
+		// Also checked Shopify/sarama code which calls this ConsumeClaim method, and don't see if there is any difference
+		// whether this method returns error or not. If it returns the error, as per current implementation, it could
+		// get printed in logs and later drained when the ConsumerGroup gets closed.
+		// For now, to be on safer side, returning nil instead of session.Context().Err() as suggested in
+		// https://github.com/Shopify/sarama/blob/5e2c2ef0e429f895c86152189f625bfdad7d3452/examples/consumergroup/main.go
+		case <-session.Context().Done():
+			return nil
 		}
 	}
-	return nil
 }
 
 func (r *Receiver) Receive(ctx context.Context) (binding.Message, error) {