com.hazelcast.jet.kafka

Class KafkaSinks

java.lang.Object

com.hazelcast.jet.kafka.KafkaSinks

public final class KafkaSinks
extends Object

Contains factory methods for Apache Kafka sinks.

Since:

Jet 3.0

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	KafkaSinks.Builder<E> A builder for Kafka sink.

Method Summary

Modifier and Type	Method and Description
static <E> KafkaSinks.Builder<E>	kafka(Properties properties) Returns a builder object that you can use to create an Apache Kafka pipeline sink.
static <E,K,V> Sink<E>	kafka(Properties properties, FunctionEx<? super E,org.apache.kafka.clients.producer.ProducerRecord<K,V>> toRecordFn) Returns a sink that publishes messages to Apache Kafka topic(s).
static <K,V> Sink<Map.Entry<K,V>>	kafka(Properties properties, String topic) Convenience for kafka(Properties, String, FunctionEx, FunctionEx) which expects Map.Entry<K, V> as input and extracts its key and value parts to be published to Kafka.
static <E,K,V> Sink<E>	kafka(Properties properties, String topic, FunctionEx<? super E,K> extractKeyFn, FunctionEx<? super E,V> extractValueFn) Convenience for kafka(Properties, FunctionEx) which creates a ProducerRecord using the given topic and the given key and value mapping functions

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

kafka

@Nonnull
public static <E,K,V> Sink<E> kafka(@Nonnull
                                             Properties properties,
                                             @Nonnull
                                             FunctionEx<? super E,org.apache.kafka.clients.producer.ProducerRecord<K,V>> toRecordFn)

Returns a sink that publishes messages to Apache Kafka topic(s). It transforms each received item to a ProducerRecord using the supplied mapping function.

The sink creates a single KafkaProducer per processor using the supplied properties.

The behavior depends on the job's processing guarantee:

• EXACTLY_ONCE: the sink will use Kafka transactions to commit the messages. Transactions are committed after a snapshot is completed. This increases the latency of the messages because they are only visible to consumers after they are committed and slightly reduces the throughput because no messages are sent between the snapshot phases.

  When using transactions pay attention to your transaction.timeout.ms config property. It limits the entire duration of the transaction since it is begun, not just inactivity timeout. It must not be smaller than your snapshot interval, otherwise the Kafka broker will roll the transaction back before Jet is done with it. Also it should be large enough so that Jet has time to restart after a failure: a member can crash just before it's about to commit, and Jet will attempt to commit the transaction after the restart, but the transaction must be still waiting in the broker. The default in Kafka 2.4 is 1 minute.

  Also keep in mind the consumers need to use isolation.level=read_committed, which is not the default. Otherwise the consumers will see duplicate messages.

• AT_LEAST_ONCE: messages are committed immediately, the sink ensure that all async operations are done at 1st snapshot phase. This ensures that each message is written if the job fails, but might be written again after the job restarts.

If you want to avoid the overhead of transactions, you can reduce the guarantee just for the sink. To do so, use the builder version and call exactlyOnce(false) on the builder.

IO failures are generally handled by Kafka producer and do not cause the processor to fail. Refer to Kafka documentation for details.

The default local parallelism for this processor is 1.

Type Parameters:

E - type of stream item

K - type of the key published to Kafka

V - type of the value published to Kafka

Parameters:

properties - producer properties which should contain broker address and key/value serializers

toRecordFn - function that extracts the key from the stream item

kafka

@Nonnull
public static <E,K,V> Sink<E> kafka(@Nonnull
                                             Properties properties,
                                             @Nonnull
                                             String topic,
                                             @Nonnull
                                             FunctionEx<? super E,K> extractKeyFn,
                                             @Nonnull
                                             FunctionEx<? super E,V> extractValueFn)

Convenience for kafka(Properties, FunctionEx) which creates a ProducerRecord using the given topic and the given key and value mapping functions

Type Parameters:

E - type of stream item

K - type of the key published to Kafka

V - type of the value published to Kafka

Parameters:

properties - producer properties which should contain broker address and key/value serializers

topic - name of the Kafka topic to publish to

extractKeyFn - function that extracts the key from the stream item

extractValueFn - function that extracts the value from the stream item

kafka

@Nonnull
public static <K,V> Sink<Map.Entry<K,V>> kafka(@Nonnull
                                                        Properties properties,
                                                        @Nonnull
                                                        String topic)

Convenience for kafka(Properties, String, FunctionEx, FunctionEx) which expects Map.Entry<K, V> as input and extracts its key and value parts to be published to Kafka.

Type Parameters:

K - type of the key published to Kafka

V - type of the value published to Kafka

Parameters:

properties - producer properties which should contain broker address and key/value serializers

topic - Kafka topic name to publish to

kafka

@Nonnull
public static <E> KafkaSinks.Builder<E> kafka(@Nonnull
                                                       Properties properties)

Returns a builder object that you can use to create an Apache Kafka pipeline sink.

The sink creates a single KafkaProducer per processor using the supplied properties.

The behavior depends on the job's processing guarantee:

• EXACTLY_ONCE: the sink will use Kafka transactions to commit the messages. This brings some overhead on the broker side, slight throughput reduction (we don't send messages between snapshot phases) and, most importantly, increases the latency of the messages because they are only visible to consumers after they are committed.

  When using transactions pay attention to your transaction.timeout.ms config property. It limits the entire duration of the transaction since it is begun, not just inactivity timeout. It must not be smaller than your snapshot interval, otherwise the Kafka broker will roll the transaction back before Jet is done with it. Also it should be large enough so that Jet has time to restart after a failure: a member can crash just before it's about to commit, and Jet will attempt to commit the transaction after the restart, but the transaction must be still waiting in the broker. The default in Kafka 2.4 is 1 minute.

• AT_LEAST_ONCE: messages are committed immediately, the sink ensure that all async operations are done at 1st snapshot phase. This ensures that each message is written if the job fails, but might be written again after the job restarts.

If you want to avoid the overhead of transactions, you can reduce the guarantee just for the sink by calling exactlyOnce(false) on the returned builder.

IO failures are generally handled by Kafka producer and do not cause the processor to fail. Refer to Kafka documentation for details.

Default local parallelism for this processor is 1.

Type Parameters:

E - type of stream item

Parameters:

properties - producer properties which should contain broker address and key/value serializers