Reprocessing Of Incoming Nacked Messages Due To Connection Loss (kafka)

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Reprocessing of Incoming Nacked Messages due to Connection Loss (Kafka)

Introduction

In a distributed system, connection loss can occur due to various reasons such as network issues, server restarts, or hardware failures. When a connection is lost, messages that were being processed may be nacked, and when the connection is re-established, the consumer may not consume the nacked messages again. This can lead to data loss and inconsistencies in the system. In this article, we will discuss how to reprocess incoming nacked messages due to connection loss using Kafka and Quarkus.

Understanding the Problem

In our current use case, we need to consume messages from a Kafka topic, process them, and send them using MQ. We are using the smallrye-kafka connector for Kafka and a custom extension for IBMMQ based on jakarta.jms for the outgoing channel. Our current solution for consuming, processing, and forwarding messages is as follows:

@Slf4j
@ApplicationScoped
public class Processor {

    private final ProcessorHelper processorHelper;

    public Processor(ProcessorHelper processorHelper) {
        this.processorHelper = processorHelper;
    }

    @Incoming("in") // kafka
    @Outgoing("out") // mq
    public Multi<String> processVpdMessage(String message) {
        return processorHelper.transformMessage(message) // maps it to a DTO, parses some fields to List<String> and returns a Multi<String>
                .onFailure()
                .invoke(this::logErrorMessage)
                .onFailure()
                .recoverWithCompletion(); // ensure the stream is not failed
    }

    private void logErrorMessage(Throwable cause) {
        log.error("Failed to process data. Not sending any messages to mq");
        if (cause instanceof BaseException) {
            ErrorCodeLogger.log(((BaseException) cause));
        } else if (cause instanceof ConstraintViolationException) {
            ErrorCodeLogger.log((ConstraintViolationException) cause);
        } else {
            ErrorCodeLogger.log(ErrorCode.UNEXPECTED_ERROR, cause);
        }
    }
}

During operation, we have noticed that there are occasional disconnections on the side of MQ. In this case, messages are nacked. If the connection is re-established, no more messages are consumed.

Expected Behavior

We expect that messages that could not be sent due to connection loss are consumed, processed, and sent to the outgoing channel when the connection is re-established.

Current Environment

We are using Quarkus 3.9.3, smallrye-reactive-messaging 4.19.0, and Java 17.

Current Configuration

Our current relevant configuration in application.yaml is as follows:

kafka:
  bootstrap:
    servers: localhost:29092
mp:
  messaging:
    incoming:
      in:
        topic: x-to-y
        connector: smallrye-kafka
        failure-strategy: ignore
        throttled:
          unprocessed-record-max-age:
            ms: 0

    out:
      vpdout:
        queue:
          name: P_QUEUE
        connector: quarkus-ibm

Solution

To reprocess incoming nacked messages due to connection loss, we need to use a combination of strategies. We will use the ignore failure strategy for the incoming channel and implement a recovery strategy for the outgoing channel.

Ignore Failure Strategy

We will set the failure-strategy to ignore for the incoming channel. This will allow the consumer to ignore any failures and continue consuming messages.

mp:
  messaging:
    incoming:
      in:
        topic: x-to-y
        connector: smallrye-kafka
        failure-strategy: ignore

Custom Recovery Strategy

We will implement a custom recovery strategy for the outgoing channel. This strategy will be responsible for reprocessing the nacked messages when the connection is re-established.

@Slf4j
@ApplicationScoped
public class RecoveryProcessor {

    private final ProcessorHelper processorHelper;

    public RecoveryProcessor(ProcessorHelper processorHelper) {
        this.processorHelper = processorHelper;
    }

    @Incoming("out") // mq
    public Multi<String> recoverNackedMessages() {
        // Get the list of nacked messages from the database or cache
        List<String> nackedMessages = getNackedMessages();

        // Process and send the nacked messages
        return nackedMessages.stream()
                .map(processorHelper::transformMessage)
                .flatMap(Multi::from);
    }

    private List<String> getNackedMessages() {
        // Implement logic to get the list of nacked messages from the database or cache
        return Collections.emptyList();
    }
}

Configure the Recovery Processor

We will configure the recovery processor to run after the connection is re-established.

mp:
  messaging:
    outgoing:
      vpdout:
        queue:
          name: P_QUEUE
        connector: quarkus-ibm
        recovery-processor: recovery-processor

Conclusion

In this article, we discussed how to reprocess incoming nacked messages due to connection loss using Kafka and Quarkus. We implemented a custom recovery strategy for the outgoing channel and configured the recovery processor to run after the connection is re-established. This solution allows us to reprocess the nacked messages when the connection is re-established, ensuring that no data is lost and the system remains consistent.

Future Work

In the future, we plan to improve the recovery processor by implementing a more efficient way to get the list of nacked messages from the database or cache. We also plan to add more features to the recovery processor, such as handling duplicate messages and implementing a more robust error handling mechanism.

References

Introduction

In our previous article, we discussed how to reprocess incoming nacked messages due to connection loss using Kafka and Quarkus. We implemented a custom recovery strategy for the outgoing channel and configured the recovery processor to run after the connection is re-established. In this article, we will answer some frequently asked questions related to reprocessing incoming nacked messages due to connection loss.

Q&A

Q: What is the purpose of the recovery processor?

A: The recovery processor is responsible for reprocessing the nacked messages when the connection is re-established. Its purpose is to ensure that no data is lost and the system remains consistent.

Q: How does the recovery processor get the list of nacked messages?

A: The recovery processor gets the list of nacked messages from the database or cache. The implementation of this logic is dependent on the specific requirements of the system.

Q: What is the difference between the ignore failure strategy and the custom recovery strategy?

A: The ignore failure strategy ignores any failures and continues consuming messages, whereas the custom recovery strategy reprocesses the nacked messages when the connection is re-established.

Q: Can I use the ignore failure strategy and the custom recovery strategy together?

A: Yes, you can use the ignore failure strategy and the custom recovery strategy together. The ignore failure strategy will ignore any failures and continue consuming messages, and the custom recovery strategy will reprocess the nacked messages when the connection is re-established.

Q: How do I configure the recovery processor to run after the connection is re-established?

A: You can configure the recovery processor to run after the connection is re-established by setting the recovery-processor property in the application.yaml file.

Q: What are the benefits of using the custom recovery strategy?

A: The benefits of using the custom recovery strategy include:

  • Ensuring that no data is lost
  • Maintaining system consistency
  • Providing a more robust error handling mechanism

Q: Can I use the custom recovery strategy with other messaging systems?

A: Yes, you can use the custom recovery strategy with other messaging systems, such as RabbitMQ or Amazon SQS.

Q: How do I implement the custom recovery strategy for other messaging systems?

A: The implementation of the custom recovery strategy for other messaging systems will depend on the specific requirements of the system and the messaging system being used.

Conclusion

In this article, we answered some frequently asked questions related to reprocessing incoming nacked messages due to connection loss. We discussed the purpose of the recovery processor, how it gets the list of nacked messages, and the difference between the ignore failure strategy and the custom recovery strategy. We also provided information on how to configure the recovery processor to run after the connection is re-established and the benefits of using the custom recovery strategy.

Future Work

In the future, we plan to provide more information on implementing the custom recovery strategy for other messaging systems and provide more examples of how to use the custom recovery strategy in different scenarios.

References