[fix] Only decompress the payload if it's not empty

The message payload is optional and in some cases only message
properties are sent. In this case, the message decompression would fail
so we only want to do the decompression if the payload is not empty.

pulsar/consumer_partition.go

@@ -1099,15 +1099,18 @@ func (pc *partitionConsumer) MessageReceived(response *pb.CommandMessage, header
 		}
 	}
 
-	// decryption is success, decompress the payload
-	uncompressedHeadersAndPayload, err := pc.Decompress(msgMeta, processedPayloadBuffer)
-	if err != nil {
-		pc.discardCorruptedMessage(pbMsgID, pb.CommandAck_DecompressionError)
-		return err
-	}
+	var uncompressedHeadersAndPayload internal.Buffer
+	// decryption is success, decompress the payload, but only if payload is not empty
+	if n := msgMeta.UncompressedSize; n != nil && *n > 0 {
+		uncompressedHeadersAndPayload, err = pc.Decompress(msgMeta, processedPayloadBuffer)
+		if err != nil {
+			pc.discardCorruptedMessage(pbMsgID, pb.CommandAck_DecompressionError)
+			return err
+		}
 
-	// Reset the reader on the uncompressed buffer
-	reader.ResetBuffer(uncompressedHeadersAndPayload)
+		// Reset the reader on the uncompressed buffer
+		reader.ResetBuffer(uncompressedHeadersAndPayload)
+	}
 
 	numMsgs := 1
 	if msgMeta.NumMessagesInBatch != nil {