nwangtw commented on issue #3198: Feature/create kafka spout URL: https://github.com/apache/incubator-heron/pull/3198#issuecomment-474967435 > I think @rohanag12’s use case is that he has multiple topics and the record from each topic will only be translated into one tuple, and emit to one stream. Basically, it is “topic1” -> “stream 1”, “topic2” -> “stream 2”, etc. So, he would like to use one KafkaSpout, subscribing to multiple topics, and have the `ConsumerRecordTransformer` declare multiple output streams, and route the translated tuple to its destined stream base on the topic of the received record. > > This pattern can save user one extra “distributor” bolt connected to the KafkaSpout. Basically, the routing logic becomes embedded in the KafkaSpout itself. But again, the trade-off of this flexibility is that developer needs to be careful not to emit multiple tuple out of one single record in ATLEAST_ONCE mode. > > So, as long as one record is only translated into one emitted tuple, then the current KafkaSpout implementation shall work in ATLEAST_ONCE mode. I see. So like N -> 1 and N -> N cases, not the 1 -> N case. Thanks.
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