@brief Wait until all outstanding produce requests, et.al, are completed.
This should typically be done prior to destroying a producer instance
to make sure all queued and in-flight produce requests are completed
before terminating.
@remark This function will call rd_kafka_poll() and thus trigger callbacks.
@returns RD_KAFKA_RESP_ERR__TIMED_OUT if \p timeout_ms was reached before all
outstanding requests were completed, else RD_KAFKA_RESP_ERR_NO_ERROR
@brief Wait until all outstanding produce requests, et.al, are completed. This should typically be done prior to destroying a producer instance to make sure all queued and in-flight produce requests are completed before terminating.
@remark This function will call rd_kafka_poll() and thus trigger callbacks.
@returns RD_KAFKA_RESP_ERR__TIMED_OUT if \p timeout_ms was reached before all outstanding requests were completed, else RD_KAFKA_RESP_ERR_NO_ERROR