Producer applications

Producer applications generate data and send it to Kafka topics. They can be used to produce messages from various sources, such as databases, files, or real-time events.

streams-bootstrap provides a structured way to build producer applications with consistent configuration handling, command-line support, and lifecycle management.

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Application lifecycle

Running an application

Producer applications are executed using the ProducerRunner, which runs the producer logic defined by the application.

Unlike Kafka Streams applications, producer applications typically:

• Run to completion and terminate automatically, or
• Run continuously when implemented as long-lived services

The execution model is fully controlled by the producer implementation and its runnable logic.

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Cleaning an application

Producer applications support a dedicated clean command.

java -jar my-producer-app.jar \
  --bootstrap-servers localhost:9092 \
  --output-topic my-topic \
  clean

The clean process can perform the following operations:

• Delete output topics
• Delete registered schemas from Schema Registry
• Execute custom cleanup hooks defined by the application

Applications can register custom cleanup logic by overriding setupCleanUp.

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Configuration

Topics

Producer applications support output topic configuration:

• --output-topic: Default output topic for produced messages
• --labeled-output-topics: Named output topics with different message types

Kafka properties

Base configuration

The following Kafka properties are configured by default for Producer applications in streams-bootstrap:

• max.in.flight.requests.per.connection = 1
• acks = all
• compression.type = gzip

Custom Kafka properties

Kafka configuration can be customized by overriding createKafkaProperties():

@Override
public Map<String, Object> createKafkaProperties() {
    return Map.of(
            ProducerConfig.RETRIES_CONFIG, 3,
            ProducerConfig.BATCH_SIZE_CONFIG, 16384,
            ProducerConfig.LINGER_MS_CONFIG, 5
    );
}

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Lifecycle hooks

Producer applications can register cleanup logic via setupCleanUp. This method allows you to attach:

• Cleanup hooks – for general cleanup logic not tied to Kafka topics
• Topic hooks – for reacting to topic lifecycle events (e.g. deletion)

Clean up

Custom cleanup logic that is not tied to Kafka topics can be registered via cleanup hooks:

@Override
public ProducerCleanUpConfiguration setupCleanUp(
        final AppConfiguration<ProducerTopicConfig> configuration) {

    return ProducerApp.super.setupCleanUp(configuration)
            .registerCleanHook(() -> {
                // Custom cleanup logic
            });
}

Topic hooks

Topic hooks should be used for topic-related cleanup or side effects, such as releasing external resources associated with a topic or logging topic deletions:

@Override
public ProducerCleanUpConfiguration setupCleanUp(
        final AppConfiguration<ProducerTopicConfig> configuration) {

    return ProducerApp.super.setupCleanUp(configuration)
            .registerTopicHook(new TopicHook() {

                @Override
                public void deleted(final String topic) {
                    // Called when a managed topic is deleted
                    System.out.println("Deleted topic: " + topic);
                }

                @Override
                public void close() {
                    // Optional closing of connections/resources
                }
            });
}

Command line interface

Producer applications inherit standard CLI options from KafkaApplication. The following CLI options are producer-specific:

Option	Description	Default
--output-topic	Default output topic	-
--labeled-output-topics	Named output topics (label1=topic1,...)	-

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Deployment

TODO