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Status
Current state: Under Discussion Adopted
Discussion thread: here
JIRA: here
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KIP-334 introduced into the Consumer the RecordDeserializationException with offsets information. That is useful to skip a poison pill but as you do not have access to the Record, it still prevents easy implementation of dead letter queue or simply logging the faulty data.
Public Interfaces
The change changes in the RecordDeserializationException would be modification of the constructor and a new method to get the ConsumerRecordare a new constructor with added argument timestampType, timestamp, keyBuffer, valueBuffer, Headers and a new enum DeserializationExceptionOrigin. New accessor methods for the added fields.
A new enum DeserializationExceptionOrigin field is allowing to differentiate if needed the origin of the error: KEY or VALUE.
As it’s only addition, it would still be compatible with existing consumer code.
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public class RecordDeserializationException extends SerializationException {
// @Deprecated
p
ublicNew enum
public enum DeserializationExceptionOrigin {
KEY,
VALUE
}
@Deprecated
public RecordDeserializationException(TopicPartition partition,
long offset,
String message,
Throwable cause);
// New constructor
public RecordDeserializationException(DeserializationExceptionOrigin origin,
TopicPartition partition,
long offset,
long timestamp,
TimestampType timestampType,
ByteBuffer Record recordkeyBuffer,
ByteBuffer valueBuffer,
Headers headers,
String message,
Throwable cause);
// New method methods
public DeserializationExceptionOrigin origin();
public TimestampType timestampType();
public long timestamp();
public ByteBuffer keyBuffer();
public ByteBuffer valueBuffer();
public RecordHeaders recordheaders();
} |
Proposed Changes
We propose to include the Record object record content and metadata to the RecordDeserializationException and provide a getConsumerRecord method that will lazily create the needed wrapper object if needed. The keyBuffer() and valueBuffer() methods will allow to access the content of the record. This would still allow us permit to access offsets and then skip the record but also to fetch the concerned data for specific processing by sending it to a dead letter queue or whatever action that makes sense.
Usage example
Here is an example of basic usage to implement a DLQ feature
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{
// …
try (KafkaConsumer<String, SimpleValue> consumer = new KafkaConsumer<>(settings())) {
// Subscribe to our topic
LOGGER.info("Subscribing to topic " + KAFKA_TOPIC);
consumer.subscribe(List.of(KAFKA_TOPIC));
LOGGER.info("Subscribed !");
try (KafkaProducer<byte[], byte[]> dlqProducer = new KafkaProducer<>(producerSettings())) {
//noinspection InfiniteLoopStatement
while (true) {
try {
final var records = consumer.poll(POLL_TIMEOUT);
LOGGER.info("poll() returned {} records", records.count());
for (var record : records) {
LOGGER.info("Fetch record key={} value={}", record.key(), record.value());
// Any processing
// ...
}
} catch (RecordDeserializationException re) {
long offset = re.offset();
Throwable t = re.getCause();
LOGGER.error("Failed to consume at partition={} offset={}", re.topicPartition().partition(), offset, t);
sendDlqRecord(dlqProducer, re.record());
LOGGER.info("Skipping offset={}", offset);
consumer.seek(re.topicPartition(), offset + 1);
} catch (Exception e) {
LOGGER.error("Failed to consume", e);
}
}
}
} finally {
LOGGER.info("Closing consumer");
}
}
void sendDlqRecord(KafkaProducer<byte[], byte[]> dlqProducer, RecordRecordDeserializationException recordre) {
var dlqRecord = new ProducerRecord<>(DLQ_TOPIC, Utils.toNullableArray(recordre.keykeyBuffer()), Utils.toNullableArray(recordre.valuevalueBuffer()));
try try {
dlqProducer.send(dlqRecord).get();
LOGGER.info("Record sent to DLQ");
} catch (Exception e) {
LOGGER.error("Failed to send corrupted record to DLQ", e);
}
} |
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This change is backward compatible and will have no impact on existing application.
The previous RecordDeserializationException constructor is deprecated as no more used.
Test Plan
- Unit test CompletedFetchTest
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- Using a raw byte array consumer and doing the deserialization in the user code. This permits dead letter queue implementation but is moving all the complexity of deseliarization deserialization to user’s code.