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Sending record keys as part of DltAwareProcessor

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Soby Chacko
2023-10-12 20:26:29 -04:00
parent f811ed0b7c
commit 4b53c839ac
3 changed files with 30 additions and 4 deletions
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14
docs/modules/ROOT/pages/kafka/kafka-streams-binder/error-handling.adoc
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@@ -189,3 +189,17 @@ public java.util.function.Function<KStream<String, String>, KStream<String, Stri
```
In this case, when the record fails, the `DltAwareProcessor`, instead of using its built-in recoverer which publishes to a DLT, uses the user provided recoverer which is a `BiConsumer` that takes the failed record and the exception thrown as arguments.
=== Handling Record Keys in DltAwareProcessor
When sending failed records to a DLT using `DltAwareProcessor`, if you want to send the record keys to the DLT topic, then you need to set the proper serializer on the DLT binding.
This is because, `DltAwareProcessor` uses `StreamBridge` which uses the regular Kafka binder (message-channel based) which by default uses a `ByteArraySerializer` for keys.
In the case of record values, Spring Cloud Stream converts the payload to proper `byte[]`; however, that is not the case with keys, as it simply pass along what it received in the header as a key.
If you are providing a non-byte array key, then that might cause class cast exceptions and to avoid that you need to set a serializer on the DLT binding as below.
Assuming that the DLT destination is `hello-dlt-1` and the record key is of String datatype.
```
spring.cloud.stream.kafka.bindings.hello-dlt-1.producer.configuration.key.serializer=org.apache.kafka.common.serialization.StringSerializer
```