如何获取 Kafka 流聚合任务的结果并将数据发送到另一个服务？

Question

我使用Kafka流来处理实时数据，我需要对窗口时间的数据进行一些聚合操作。

我有两个关于聚合操作的问题。

1. 如何获取汇总数据？我需要将它发送到第三个服务。
2. 聚合操作后，我无法向第三个服务发送消息，代码无法运行。

这是我的代码：

stream = builder.stream("topic");
windowedKStream = stream.map(XXXXX).groupByKey().windowedBy("5mins");
ktable = windowedKStream.aggregate(()->"", new Aggregator(K,V,result));

// my data is stored in 'result' variable, but I can't get it at the end of the 5 mins window. 
// I need to send the 'result' to a 3rd service. But I don't know where to temporarily store it and then how to get it.

// below is the code the call a 3rd service, but the code can't be executed(reachable).
// I think it should be executed every 5 mins when thewindows is over. But it isn't.

result = httpclient.execute('result');

Answer 1

我想可能想做这样的事情：

ktable.toStream().foreach((k,v) -> httpclient.execute(v));

每次更新KTable（禁用缓存），都会将更新记录发送到下游，并以v为当前聚合结果执行foreach。