我们有以下问题需要与卡夫卡流解决:卡夫卡流DSL:聚合,充实和发送通过
1-获取消息。每条消息都标有eventId(消息更新事件)和correlationId(每条消息都是唯一的)。
2-合计从该消息的一些国家(基于事件ID),并追加它在本地存储
3-现有的状态充实该消息为充分凝聚状态该事件,并通过发送到输出话题
要点是我们不能真的失去一条消息,并且它必须一直以最新的聚合状态(我们在消息处理期间我们实际评估的)来丰富传入的消息。
从我迄今所看到的,我们不能只用简单的聚合(类似的东西:)
stateMessageStream
.map((k, v) => new KeyValue[String, StateMessage](k, v))
.mapValues[StateMessageWithMarkets](sm => {StateMessageWithMarkets(Some(sm), extract(sm))})
.groupBy((k, _) => k, stringSerde, marketAggregatorSerde)
.aggregate[StateMessageWithMarkets](() => StateMessageWithMarkets(), (_, v, aggregatedState) => aggregatedState.updateModelMarketsWith(v), marketAggregatorSerde, kafkaStoreName)
.to(stringSerde, marketAggregatorSerde, kafkaOutTopic)
,因为只有聚集在间隔产生新的记录,这将意味着有两个传入的消息,我们不妨生成只有单个聚合输出消息(所以我们失去了一条消息)
我第二次尝试如何实现这基本上是两个流,一个用于聚合,第二个用于普通消息。最后,我们可以加入两个流回到一起使用连接操作的基础上的correlationID作为重点 - 我们可以用正确的信息传达给适当的状态:
val aggregatedStream : KStream[String, MarketAggregator] = stateMessageStream
.map((k, v) => new KeyValue[String, StateMessage](k, v))
.mapValues[StateMessage](v => {
log.debug("Received State Message, gameId: " + v.metadata().gtpId() + ", correlationId: " + v.correlationId)
v})
.mapValues[MarketAggregator](sm => {MarketAggregator(sm.correlationId, extract(sm))})
.groupBy((k, v) => k, stringSerde, marketAggregatorSerde)
.aggregate[MarketAggregator](() => MarketAggregator(), (_, v, aggregatedState) => aggregatedState.updateModelMarketsWith(v), marketAggregatorSerde, kafkaStoreName)
.toStream((k, v) => v.correlationId)
stateMessageStream
.selectKey[String]((k, v) => v.correlationId)
.leftJoin[MarketAggregator, StateMessageWithMarkets](aggregatedStream, (stateMessage : StateMessage, aggregatedState : MarketAggregator) => StateMessageWithMarkets(Some(stateMessage), aggregatedState.modelMarkets, stateMessage.correlationId),
JoinWindows.of(10000),
stringSerde, stateMessageSerde, marketAggregatorSerde)
.mapValues[StateMessageWithMarkets](v => {
log.debug("Producing aggregated State Message, gameId: " + v.stateMessage.map(_.metadata().gtpId()).getOrElse("unknown") +
", correlationId: " + v.stateMessage.map(_.correlationId).getOrElse("unknown"))
v
})
.to(stringSerde, stateMessageWithMarketsSerde, kafkaOutTopic)
然而,这似乎并没有被任何工作 - 对于两个传入的消息,我仍然只在输出主题上获得最新聚合状态的单个消息。
有人可以解释为什么以及正确的解决方案是什么?