@systemcraftsman MicroProfile Open-source community specification for Cloud-Native Java applications. A community of individuals, organizations, and vendors collaborating.
@systemcraftsman What is wrong with JMS and Message Driven Beans? Heavyweight (mostly because of XA) Incompatible with popular brokers like Kafka No support for asynchronous IO
@systemcraftsman Concepts Internal Channels: In-memory messaging that creates a reactive chain of processing of beans External Channels: Channels are to be connected to external systems like Kafka or AMQP broker
@systemcraftsman Concepts Internal Channels: In-memory messaging that creates a reactive chain of processing of beans External Channels: Channels are to be connected to external systems like Kafka or AMQP broker External channels Internal channels
@systemcraftsman Using @Incoming import org.eclipse.microprofile.reactive.messaging.Incoming; import javax.enterprise.context.ApplicationScoped; @ApplicationScoped public class PriceConsumer { @Incoming("prices") public void consume(double price) { // process your price. } } Java file
@systemcraftsman Using @Incoming @Incoming("prices") public CompletionStage consume(Message msg) { // access record metadata var metadata = msg.getMetadata(IncomingKafkaRecordMetadata.class).orElseThrow(); // process the message payload. double price = msg.getPayload(); // Acknowledge the incoming message (commit the offset) return msg.ack(); } Java file
@systemcraftsman Commit Strategies throttled keeps track of received messages and commits an offset of the latest acked message in sequence (meaning, all previous messages were also acked). This is the default if enable.auto.commit is not explicitly set to true. latest commits the record offset received by the Kafka consumer as soon as the associated message is acknowledged (if the offset is higher than the previously committed offset). ignore performs no commit. This strategy is the default strategy when the consumer is explicitly configured with enable.auto.commit to true.
@systemcraftsman Error Handling fail fail the application, no more records will be processed (default strategy). The offset of the record that has not been processed correctly is not committed. ignore the failure is logged, but the processing continue. The offset of the record that has not been processed correctly is committed. dead-letter-queue the offset of the record that has not been processed correctly is committed, but the record is written to a Kafka dead letter topic.
@systemcraftsman Consumer Groups Single consumer thread inside a consumer group Multiple consumer threads inside a consumer group Multiple consumer applications inside a consumer group Pub/Sub: Multiple consumer groups subscribed to a topic 4 Patterns for consuming:
@systemcraftsman Consumer Groups Pub/Sub: Multiple consumer groups subscribed to a topic mp.messaging.incoming.somechannel.group.id=someid mp.messaging.incoming.somechannel.group.id=someotherid
@systemcraftsman Using @Outgoing import io.smallrye.mutiny.Multi; import org.eclipse.microprofile.reactive.messaging.Outgoing; import javax.enterprise.context.ApplicationScoped; import java.time.Duration; import java.util.Random; @ApplicationScoped public class KafkaPriceProducer { private final Random random = new Random(); @Outgoing("prices") public Multi generate() { // Build an infinite stream of random prices // It emits a price every second return Multi.createFrom().ticks().every(Duration.ofSeconds(1)) .map(x -> random.nextDouble()); } } Java file
@systemcraftsman Using @Emitter import java.util.concurrent.CompletableFuture; import org.eclipse.microprofile.reactive.messaging.Channel; import org.eclipse.microprofile.reactive.messaging.Emitter; ...some imports omitted... @Path("/prices") public class PriceResource { @Inject @Channel("prices") Emitter priceEmitter; @POST @Consumes(MediaType.TEXT_PLAIN) public void addPrice(Double price) { priceEmitter.send(Message.of(price) .withAck(() -> { // Called when the message is acked return CompletableFuture.completedFuture(null); }) .withNack(throwable -> { // Called when the message is nacked return CompletableFuture.completedFuture(null); })); } } Java file
@systemcraftsman JSON public class Fruit { public String name; public int price; public Fruit() { } public Fruit(String name, int price) { this.name = name; this.price = price; } } @ApplicationScoped public class FruitProcessor { private static final double CONVERSION_RATE = 0.88; @Incoming("fruit-in") @Outgoing("fruit-out") @Broadcast public Fruit process(Fruit fruit) { fruit.price = fruit.price * CONVERSION_RATE; return fruit; } } Java file Java file
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