Beam java SDK 2.10.0 with Kafka source and Dataflow runner: windowed Count.perElement never fires data out

Question

我在 Google DataFlow

上遇到运行 Beam SDK 到 2.10.0 作业的问题

流程很简单：我使用 Kafka 作为源，然后应用 Fixed windows，然后按键计数元素。但看起来数据永远不会离开计数阶段，直到工作耗尽。 Count.PerElement/Combine.perKey(Count)/Combine.GroupedValues.out0 的输出集合始终为零。仅在耗尽数据流作业后才发布元素。

代码如下：

public KafkaProcessingJob(BaseOptions options) {

    PCollection<GenericRecord> genericRecordPCollection = Pipeline.create(options)
                     .apply("Read binary Kafka messages", KafkaIO.<String, byte[]>read()
                           .withBootstrapServers(options.getBootstrapServers())
                           .updateConsumerProperties(configureConsumerProperties())
                           .withCreateTime(Duration.standardMinutes(1L))
                           .withTopics(inputTopics)
                           .withReadCommitted()
                           .commitOffsetsInFinalize()
                           .withKeyDeserializer(StringDeserializer.class)
                           .withValueDeserializer(ByteArrayDeserializer.class))

                    .apply("Map binary message to Avro GenericRecord", new DecodeBinaryKafkaMessage());

                    .apply("Apply windowing to records", Window.into(FixedWindows.of(Duration.standardMinutes(5)))
                                       .triggering(Repeatedly.forever(AfterWatermark.pastEndOfWindow()))
                                       .discardingFiredPanes()
                                       .withAllowedLateness(Duration.standardMinutes(5)))

                    .apply("Write aggregated data to BigQuery", MapElements.into(TypeDescriptors.strings()).via(rec -> getKey(rec)))
                            .apply(Count.<String>perElement())
                            .apply(
                                new WriteWindowedToBigQuery<>(
                                    project,
                                    dataset,
                                    table,
                                    configureWindowedTableWrite()));   
}

private Map<String, Object> configureConsumerProperties() {
    Map<String, Object> configUpdates = Maps.newHashMap();
    configUpdates.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");

    return configUpdates;
}

private static String getKey(GenericRecord record) {
    //extract key
}

看起来流量永远不会离开.apply(Count.<String>perElement())

的舞台

有人可以帮忙吗？

Answer 1

我找到原因了。

与这里使用的TimestampPolicy有关(.withCreateTime(Duration.standardMinutes(1L)))。

由于我们的 Kafka 主题中存在空分区，因此从未使用默认的 TimestampPolicy 推进主题水印。我需要实施自定义策略来解决问题。

Beam java SDK 2.10.0 with Kafka source and Dataflow runner: windowed Count.perElement never fires data out

Beam java SDK 2.10.0 with Kafka source and Dataflow runner: windowed Count.perElement never fires data out

java

google-cloud-dataflow

apache-beam