Kafka Stream 如何使用 KTable#Suppress 发送最终聚合? [英] How does Kafka Stream send final aggregation with KTable#Suppress?
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问题描述
我想做的是:
- 使用主题中的记录
- 计算每 1 秒窗口的值
- 检测记录数
- 的窗口4
- 将最终结果发送到另一个主题
我使用抑制来发送最终结果,但出现了这样的错误.
I use suppress to send final result, but I got an error like this.
09:18:07,963 ERROR org.apache.kafka.streams.processor.internals.ProcessorStateManager
- task [1_0] Failed to flush state store KSTREAM-AGGREGATE-STATE-STORE-0000000002:
java.lang.ClassCastException: org.apache.kafka.streams.kstream.Windowed cannot be cast to java.lang.String
at org.apache.kafka.common.serialization.StringSerializer.serialize(StringSerializer.java:28)
at org.apache.kafka.streams.kstream.internals.suppress.KTableSuppressProcessor.buffer(KTableSuppressProcessor.java:86)
at org.apache.kafka.streams.kstream.internals.suppress.KTableSuppressProcessor.process(KTableSuppressProcessor.java:78)
at org.apache.kafka.streams.kstream.internals.suppress.KTableSuppressProcessor.process(KTableSuppressProcessor.java:37)
at org.apache.kafka.streams.processor.internals.ProcessorNode.process(ProcessorNode.java:115)
at org.apache.kafka.streams.processor.internals.ProcessorContextImpl.forward(ProcessorContextImpl.java:146)
.....
我认为我的代码与开发人员指南中的示例相同.有什么问题?我的代码在这里.
I think my code is the same as example in developer guide. What's the problem? My code here.
final KStream<String, String> views = builder.stream("fluent-newData");
final KTable<Windowed<String>, Long> anomalousUsers = views
.map((key, value) -> {
JSONObject message = JSONObject.fromObject(value);
String[] strArry = message.getString("detail").split(",");
return KeyValue.pair(strArry[0], value);
})
.groupByKey()
.windowedBy(TimeWindows.of(Duration.ofSeconds(1))
.grace(Duration.ofSeconds(20)))
.count()
.suppress(Suppressed.untilWindowCloses(unbounded()))
.filter((windowedUserId, count) -> count < 4);
final KStream<String, String> anomalousUsersForConsole = anomalousUsers
.toStream()
.filter((windowedUserId, count) -> count != null)
.map((windowedUserId, count) -> new KeyValue<>(windowedUserId.toString(), windowedUserId.toString() +" c:" + count.toString()));
anomalousUsersForConsole.to("demo-count-output", Produced.with(stringSerde, stringSerde));
推荐答案
Windowed cannot be cast to java.lang.String" 通常在您没有直接指定 serdes 时抛出.
"Windowed cannot be cast to java.lang.String" usually thrown when you haven't specified serdes directly.
在构建 stream(..)
时,直接指定 Consumed 实例,如下所示:
when you building stream(..)
, specify directly Consumed instance like the following:
builder.stream("fluent-newData", Consumed.with(Serdes.String(), Serdes.String()))
同样对于 groupByKey()
你需要像下面这样传递 Grouped
:
also for groupByKey()
you need to pass Grouped
like the following:
.groupByKey(Grouped.with(Serdes.String(), Serdes.String()))
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