apache-kafka - 加入使用 Avro 模式定义的两个 Kafka 流时如何编写 ValueJoiner?
问题描述
我正在构建一个电子商务应用程序,我目前正在处理两个数据馈送:订单执行和销售中断。由于各种原因,失败的销售将是无效的执行。损坏的销售将具有与订单相同的订单参考编号,因此连接是在订单参考 # 和订单项 # 上。
目前,我有两个主题 -orders
和broken
。两者都使用 Avro Schemas 定义,并使用 SpecificRecord 构建。关键是OrderReferenceNumber
。
字段orders
:OrderReferenceNumber, Timestamp, OrderLine, ItemNumber, Quantity
字段broken
:OrderReferenceNumber, OrderLine, Timestamp
通过运行生成相应的 Java 类
mvn clean package
我需要左连接orders
并broken
在输出中包含以下字段:OrderReferenceNumber, Timestamp, BrokenSaleTimestamp, OrderLine, ItemNumber, Quantity
这是我的代码:
public static void main(String[] args) {
// Declare variables
final Map<String, String> avroSerdeConfig = Collections.singletonMap(KafkaAvroSerializerConfig.SCHEMA_REGISTRY_URL_CONFIG, "http://localhost:8081");
// Add Kafka Streams Properties
Properties streamsProperties = new Properties();
streamsProperties.put(StreamsConfig.APPLICATION_ID_CONFIG, "orderProcessor");
streamsProperties.put(StreamsConfig.BOOTSTRAP_SERVERS_CONFIG, "localhost:9092");
streamsProperties.put(ConsumerConfig.AUTO_OFFSET_RESET_CONFIG, "earliest");
streamsProperties.put(StreamsConfig.DEFAULT_KEY_SERDE_CLASS_CONFIG, Serdes.String().getClass());
streamsProperties.put(StreamsConfig.DEFAULT_VALUE_SERDE_CLASS_CONFIG, SpecificAvroSerde.class);
streamsProperties.put(KafkaAvroSerializerConfig.SCHEMA_REGISTRY_URL_CONFIG, "localhost:8081");
// Specify Kafka Topic Names
String orderTopic = "com.ecomapp.input.OrderExecuted";
String brokenTopic = "com.ecomapp.input.BrokenSale";
// Specify Serializer-Deserializer or Serdes for each Message Type
Serdes.StringSerde stringSerde = new Serdes.StringSerde();
Serdes.LongSerde longSerde = new Serdes.LongSerde();
// For the Order Executed Message
SpecificAvroSerde<OrderExecuted> ordersSpecificAvroSerde = new SpecificAvroSerde<OrderExecuted>();
ordersSpecificAvroSerde.configure(avroSerdeConfig, false);
// For the Broken Sale Message
SpecificAvroSerde<BrokenSale> brokenSpecificAvroSerde = new SpecificAvroSerde<BrokenSale>();
brokenSpecificAvroSerde.configure(avroSerdeConfig, false);
StreamsBuilder streamBuilder = new StreamsBuilder();
KStream<String, OrderExecuted> orders = streamBuilder
.stream(orderTopic, Consumed.with(stringSerde, ordersSpecificAvroSerde))
.selectKey((key, orderExec) -> orderExec.getMatchNumber().toString());
KStream<String, BrokenSale> broken = streamBuilder
.stream(brokenTopic, Consumed.with(stringSerde, brokenSpecificAvroSerde))
.selectKey((key, brokenS) -> brokenS.getMatchNumber().toString());
KStream<String, JoinOrdersExecutedNonBroken> joinOrdersNonBroken = orders
.leftJoin(broken,
(orderExec, brokenS) -> JoinOrdersExecutedNonBroken.newBuilder()
.setOrderReferenceNumber((Long) orderExec.get("OrderReferenceNumber"))
.setTimestamp((Long) orderExec.get("Timestamp"))
.setBrokenSaleTimestamp((Long) brokenS.get("Timestamp"))
.setOrderLine((Long) orderExec.get("OrderLine"))
.setItemNumber((String) orderExec.get("ItemNumber"))
.setQuantity((Long) orderExec.get("Quantity"))
.build(),
JoinWindows.of(TimeUnit.MILLISECONDS.toMillis(1))
Joined.with(stringSerde, ordersSpecificAvroSerde, brokenSpecificAvroSerde))
.peek((key, value) -> System.out.println("key = " + key + ", value = " + value));
KafkaStreams orderStreams = new KafkaStreams(streamBuilder.build(), streamsProperties);
orderStreams.start();
// print the topology
System.out.println(orderStreams.localThreadsMetadata());
// shutdown hook to correctly close the streams application
Runtime.getRuntime().addShutdownHook(new Thread(orderStreams::close));
}
当我运行它时,我得到以下 maven 编译错误:
[ERROR] /Tech/Projects/jCom/src/main/java/com/ecomapp/kafka/orderProcessor.java:[96,26] incompatible types: cannot infer type-variable(s) VO,VR,K,V,VO
(argument mismatch; org.apache.kafka.streams.kstream.Joined<K,V,com.ecomapp.input.BrokenSale> cannot be converted to org.apache.kafka.streams.kstream.Joined<java.lang.String,com.ecomapp.OrderExecuted,com.ecomapp.input.BrokenSale>)
问题真的在于定义我的ValueJoiner
. 当涉及 Avro 模式时,Confluent 文档不太清楚如何执行此操作(我也找不到示例)。定义这个的正确方法是什么?
解决方案
不确定为什么 Java 无法解析该类型。
尝试:
Joined.<String,OrderExecuted,BrokenSale>with(stringSerde, ordersSpecificAvroSerde, brokenSpecificAvroSerde))
明确指定类型。
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