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| @Bean | |
| public KStream<?, ?> kstreamTombstone(StreamsBuilder streamsBuilder) { | |
| KStream<String, IotEvent> inbound = streamsBuilder.stream(inputTopic, Consumed.with(Serdes.String(), iotEventSerde())); | |
| inbound | |
| .peek((key, value) -> LOG.debug("incoming message: {} {}", key, value)) | |
| //check for a null value (tombstone) and set delete flag if necessary | |
| .mapValues((readOnlyKey, value) -> { | |
| if (value == null) { | |
| value = new IotEvent(); | |
| value.setDelete(true); | |
| } | |
| return value; | |
| }) | |
| //re-partition our data on a new key | |
| .groupBy((key, value) -> eventKey(value), Grouped.with(Serdes.String(), iotEventSerde())) | |
| //check for delete flag and return null if true | |
| .aggregate(IotEventMetric::new, | |
| (key, value, aggregate) -> { | |
| if (value.isDelete()) { | |
| return null; | |
| } | |
| return aggregate.add(value); | |
| }, | |
| Materialized.<String, IotEventMetric, KeyValueStore<Bytes, byte[]>>as("eventstore") | |
| .withValueSerde(iotEventMetricSerde()) | |
| ) | |
| .toStream() | |
| //publish our results to a topic | |
| .to("output-topic", Produced.with(Serdes.String(), iotEventMetricSerde())); | |
| return inbound; | |
| } |
@suikast42 Hi there, the eventKey(value) method could return any string - it's just an example of building a new key to aggregate on. And the iotEventSerde() method would just return an Avro Serde - or whatever Serde you need for the data you're working with. Does that make sense?
I found it out. Thanks a lot :-D
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I am hanging on the basic with working with KStrean and grouping.
Can you provide the implementation of iotEventSerde() and eventKey(value) ?