在librdkafka中，每次调用produce()后都会调用dr_cb()

我正在开发 C++ Kafka 客户端:librdkafka.库在这里 https://github.com/edenhill/librdkafka/blob/master/examples/rdkafka_example.cpp.每次调用Producer类中的produce()，是否调用了dr_cb()函数(见下面代码)?

I am working on C++ Kafka client: librdkafka. The lib is here https://github.com/edenhill/librdkafka/blob/master/examples/rdkafka_example.cpp. Each time produce() in Producer class is called, is the dr_cb() function (see the following code) called?

/**
* Delivery Report callback class
*/
class DeliveryReportCb {
public:
virtual void dr_cb (Message &message) = 0;
};