java - 如何对使用 session 窗口的 kafka 流应用程序进行单元测试

Question

我正在使用 Kafka Stream 2.1

我正在尝试为聚合的流应用程序编写一些测试
一些事件通过它们的键(即通过相关 ID)使用具有 300 毫秒不活动间隙的 session 窗口。

这是由方法表示的聚合实现:

    private static final int INACTIVITY_GAP = 300;

    public KStream<String, AggregatedCustomObject> aggregate(KStream<String, CustomObject> source) {

        return source
                // group by key (i.e by correlation ID)
                .groupByKey(Grouped.with(Serdes.String(), new CustomSerde()))
                // Define a session window with an inactivity gap of 300 ms
                .windowedBy(SessionWindows.with(Duration.ofMillis(INACTIVITY_GAP)).grace(Duration.ofMillis(INACTIVITY_GAP)))
                .aggregate(
                        // initializer
                        () -> new AggregatedCustomObject(),
                        // aggregates records in same session
                        (s, customObject, aggCustomObject) -> {
                            // ...
                            return aggCustomObject;
                        },
                        // merge sessions
                        (s, aggCustomObject1, aggCustomObject2) -> {
                            // ...
                            return aggCustomObject2;
                        },
                        Materialized.with(Serdes.String(), new AggCustomObjectSerde())
                )
                .suppress(Suppressed.untilWindowCloses(unbounded()))
                .toStream()
                .selectKey((stringWindowed, aggCustomObject) -> "someKey");
    ;
    }

此流处理按预期工作。但对于单元测试，情况就不同了。

我的测试流配置如下所示:

        // ...

        props.setProperty(StreamsConfig.APPLICATION_ID_CONFIG, "test");
        props.setProperty(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "dummy:1234");
        props.setProperty(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass().getName());
        props.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, myCustomObjectSerde.getClass());
        // disable cache
        props.put(StreamsConfig.CACHE_MAX_BYTES_BUFFERING_CONFIG, 0);
        // commit ASAP
        props.put(StreamsConfig.COMMIT_INTERVAL_MS_CONFIG, 0);


        StreamsBuilder builder = new StreamsBuilder();
        aggregate(builder.stream(INPUT_TOPIC), OUTPUT_TOPIC, new AggCustomObjectSerde())
.to(OUTPUT_TOPIC);

        Topology topology = builder.build();
        TopologyTestDriver testDriver = new TopologyTestDriver(topology, props);
        ConsumerRecordFactory<String, MyCustomObject> factory = new ConsumerRecordFactory<>(INPUT_TOPIC, new StringSerializer(), myCustomSerializer)

        // ...

测试如下所示:

List<ConsumerRecord<byte[], byte[]>> records = myCustomMessages.stream()
                .map(myCustomMessage -> factory.create(INPUT_TOPIC, myCustomMessage.correlationId, myCustomMessage))
                .collect(Collectors.toList());
testDriver.pipeInput(records);

ProducerRecord<String, AggregatedCustomMessage> record = testDriver.readOutput(OUTPUT_TOPIC, new StringDeserializer(), myAggregatedCustomObjectSerde);

问题是， record始终为空。
我尝试了很多东西:

循环读取，超时

更改配置中的提交间隔，以便尽快提交结果

紧随其后发送带有不同键的附加记录(以触发窗口关闭，如 KafkaStream 事件时间基于记录时间戳)

调用advanceWallClockTime测试驱动方法

好吧，没有什么帮助。有人可以告诉我我缺少什么，我应该如何测试基于 session 窗口的流应用程序？

非常感谢

Answer 1

SessionWindows使用 event-time 而不是 wall-clock 。尝试正确设置记录的事件时间以模拟不活动间隙。就像是:

testDriver.pipeInput(factory.create(INPUT_TOPIC, key1, record1, eventTimeMs));
testDriver.pipeInput(factory.create(INPUT_TOPIC, key2, record2, eventTimeMs + inactivityGapMs));

但首先，您需要自定义 TimestampExtractor像:

 public static class RecordTimestampExtractor implements TimestampExtractor {

    @Override
    public long extract(ConsumerRecord<Object, Object> record, long previousTimestamp) {
      return record.timestamp();
    }
  }

必须像这样注册:

 streamProperties.setProperty(
        StreamsConfig.DEFAULT_TIMESTAMP_EXTRACTOR_CLASS_CONFIG,
        RecordTimestampExtractor.class.getName()
    );