@brief Consumes messages from topic \p rkt and \p partition, calling
the provided callback for each consumed messsage.
rd_kafka_consume_callback() provides higher throughput performance
than both rd_kafka_consume() and rd_kafka_consume_batch().
\p timeout_ms is the maximum amount of time to wait for one or more messages
to arrive.
The provided \p consume_cb function is called for each message,
the application \b MUST \b NOT call rd_kafka_message_destroy() on the
provided \p rkmessage.
The \p opaque argument is passed to the 'consume_cb' as \p opaque.
@returns the number of messages processed or -1 on error.
@brief Consumes messages from topic \p rkt and \p partition, calling the provided callback for each consumed messsage.
rd_kafka_consume_callback() provides higher throughput performance than both rd_kafka_consume() and rd_kafka_consume_batch().
\p timeout_ms is the maximum amount of time to wait for one or more messages to arrive.
The provided \p consume_cb function is called for each message, the application \b MUST \b NOT call rd_kafka_message_destroy() on the provided \p rkmessage.
The \p opaque argument is passed to the 'consume_cb' as \p opaque.
@returns the number of messages processed or -1 on error.
@sa rd_kafka_consume()