private void setServiceName(LogData.Builder builder) {
                if (StringUtil.isEmpty(serviceName) && StringUtil.isNotEmpty(builder.getService())) {
                    serviceName = builder.getService();
                } else if (StringUtil.isNotEmpty(serviceName)) {
                    builder.setService(serviceName);
                }
            }
If this is not the first element of the streaming,
use the previous not-null name as the service name.
oap-server/server-receiver-plugin/skywalking-log-receiver-plugin/src/main/java/org/apache/skywalking/oap/server/receiver/log/provider/handler/grpc/LogReportServiceGrpcHandler.java