org.apache.kafka.connect.errors.DataException：记录默认值为null的JSON无效

Question

我有一个使用KafKaavroSerializer生成的Kafka Avro主题。
我的独立属性如下所示。
我正在使用Confluent 4.0.0运行Kafka Connect。

key.converter=io.confluent.connect.avro.AvroConverter
value.converter=io.confluent.connect.avro.AvroConverter
key.converter.schema.registry.url=<schema_registry_hostname>:8081
value.converter.schema.registry.url=<schema_registry_hostname>:8081
key.converter.schemas.enable=true
value.converter.schemas.enable=true
internal.key.converter=org.apache.kafka.connect.json.JsonConverter
internal.value.converter=org.apache.kafka.connect.json.JsonConverter
internal.key.converter.schemas.enable=false
internal.value.converter.schemas.enable=false

当我在独立模式下运行hdfs接收器的Kafka连接器时,收到以下错误消息：

[2018-06-27 17:47:41,746] ERROR WorkerSinkTask{id=camus-email-service-0} Task threw an uncaught and unrecoverable exception (org.apache.kafka.connect.runtime.WorkerTask)
org.apache.kafka.connect.errors.DataException: Invalid JSON for record default value: null
    at io.confluent.connect.avro.AvroData.defaultValueFromAvro(AvroData.java:1640)
    at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1527)
    at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1410)
    at io.confluent.connect.avro.AvroData.toConnectSchema(AvroData.java:1290)
    at io.confluent.connect.avro.AvroData.toConnectData(AvroData.java:1014)
    at io.confluent.connect.avro.AvroConverter.toConnectData(AvroConverter.java:88)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.convertMessages(WorkerSinkTask.java:454)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.poll(WorkerSinkTask.java:287)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.iteration(WorkerSinkTask.java:198)
    at org.apache.kafka.connect.runtime.WorkerSinkTask.execute(WorkerSinkTask.java:166)
    at org.apache.kafka.connect.runtime.WorkerTask.doRun(WorkerTask.java:170)
    at org.apache.kafka.connect.runtime.WorkerTask.run(WorkerTask.java:214)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
    at java.util.concurrent.FutureTask.run(FutureTask.java:266)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
    at java.lang.Thread.run(Thread.java:745)
[2018-06-27 17:47:41,748] ERROR WorkerSinkTask{id=camus-email-service-0} Task is being killed and will not recover until manually restarted (    org.apache.kafka.connect.runtime.WorkerTask)
[2018-06-27 17:52:19,554] INFO Kafka Connect stopping (org.apache.kafka.connect.runtime.Connect).

当我使用kafka-avro-console-consumer传递模式注册表时，我会对Kafka消息进行反序列化。

即：

/usr/bin/kafka-avro-console-consumer --bootstrap-server <kafka-host>:9092 --topic <KafkaTopicName> --property schema.registry.url=<schema_registry_hostname>:8081

Answer 1

将“subscription”列的数据类型更改为Union数据类型可以解决此问题。Avroconverters能够反序列化消息。