Package io.smallrye.reactive.messaging.kafka.transactions

Interface KafkaTransactions<T>

  • Type Parameters:
    T - emitted payload type
    All Superinterfaces:
    io.smallrye.reactive.messaging.EmitterType
    All Known Implementing Classes:
    KafkaTransactionsImpl
    @Experimental("Experimental API")
public interface KafkaTransactions<T>
extends io.smallrye.reactive.messaging.EmitterType
    Emitter interface for producing records in a Kafka transaction. This interface defines a custom Emitter for implementing Kafka Producer Transactions and Exactly-once processing.

    Transactional producer: 

     

 @Inject @Channel("tx-out-channel") KafkaTransactions<String> txEmitter;

 // ...
 Uni<Integer> txWork = txEmitter.withTransaction(emitter -> {
     emitter.send("a");
     emitter.send("b");
     emitter.send("c");
     return Uni.createFrom().item(3);
 });

 // ...

    Exactly-once processing: 

     

 @Inject @Channel("tx-out-channel") KafkaTransactions<String> txEmitter;

 @Incoming("in-channel")
 Uni<Void> process(KafkaRecordBatch<String, String> batch) {
     return txEmitter.withTransaction(batch, emitter -> {
         for (KafkaRecord<String, String> rec : batch) {
           txEmitter.send(KafkaRecord.of(record.getKey(), record.getPayload()));
         }
         return Uni.createFrom().voidItem();
     });
 }

    • Method Detail

      • withTransaction

        @CheckReturnValue
<R> io.smallrye.mutiny.Uni<R> withTransaction​(Function<TransactionalEmitter<T>,​io.smallrye.mutiny.Uni<R>> work)
        Produce records in a Kafka transaction.

        The given processing function receives a TransactionalEmitter for producing records, and returns a Uni that will provide the result for a successful transaction.

        If this method is called on a Vert.x context, the processing function is also called on that context. Otherwise, it is called on the sending thread of the producer.

        If the processing completes successfully, the producer is flushed and the transaction is committed. If the processing throws an exception, returns a failing Uni, or marks the TransactionalEmitter for abort, the transaction is aborted.

        Type Parameters:
        R - the return type
        Parameters:
        work - the processing function for producing records.
        Returns:
        the Uni representing the result of the transaction. If the transaction completes successfully, it will complete with the item returned from the work function. If the transaction completes with failure, it will fail with the reason.
        Throws:
        IllegalStateException - if a transaction is already in progress.

      • withTransaction

        @CheckReturnValue
<R> io.smallrye.mutiny.Uni<R> withTransaction​(org.eclipse.microprofile.reactive.messaging.Message<?> message,
                                              Function<TransactionalEmitter<T>,​io.smallrye.mutiny.Uni<R>> work)
        Produce records in a Kafka transaction, by processing the given message exactly-once.

        If the processing completes successfully, before committing the transaction, the topic partition offsets of the given message will be committed to the transaction. If the processing needs to abort, after aborting the transaction, the consumer's position is reset to the last committed offset, effectively resuming the consumption from that offset.

        Parameters:
        message - the incoming Kafka message expected to contain a metadata IncomingKafkaRecordBatchMetadata or IncomingKafkaRecordMetadata.
        work - the processing function for producing records.
        Returns:
        the Uni representing the result of the transaction. If the transaction completes successfully, it will complete with the item returned from the work function. If the transaction completes with failure, it will fail with the reason.
        Throws:
        IllegalStateException - if a transaction is already in progress.

      • withTransactionAndAck

        @CheckReturnValue
default io.smallrye.mutiny.Uni<Void> withTransactionAndAck​(org.eclipse.microprofile.reactive.messaging.Message<?> batchMessage,
                                                           Function<TransactionalEmitter<T>,​io.smallrye.mutiny.Uni<Void>> work)
        Produce records in a Kafka transaction, by processing the given batch message exactly-once. This is a convenience method that ignores the item returned by the transaction and returns the Uni which
        • acks the given message if the transaction is successful.
        • nacks the given message if the transaction is aborted.
        Parameters:
        batchMessage - the batch message expected to contain a metadata of IncomingKafkaRecordBatchMetadata.
        work - function for producing records.
        Returns:
        the Uni acking or negative acking the message depending on the result of the transaction.
        Throws:
        IllegalStateException - if a transaction is already in progress.
        See Also:
        withTransaction(Message, Function)

      • isTransactionInProgress

        boolean isTransactionInProgress()
        Returns:
        true if a transaction is in progress.