リアクティブアプリケーションにおけるSpring AMQP

@Autowired
private AmqpAdmin amqpAdmin;

@Autowired
private DestinationsConfig destinationsConfig;

@PostConstruct
public void setupQueueDestinations() {
    destinationsConfig.getQueues()
        .forEach((key, destination) -> {
            Exchange ex = ExchangeBuilder.directExchange(
              destination.getExchange())
              .durable(true)
              .build();
            amqpAdmin.declareExchange(ex);
            Queue q = QueueBuilder.durable(
              destination.getRoutingKey())
              .build();
            amqpAdmin.declareQueue(q);
            Binding b = BindingBuilder.bind(q)
              .to(ex)
              .with(destination.getRoutingKey())
              .noargs();
            amqpAdmin.declareBinding(b);
        });
}

@SpringBootApplication
@EnableConfigurationProperties(DestinationsConfig.class)
@RestController
public class SpringWebfluxAmqpApplication {

   //... other members omitted

    @Autowired
    private AmqpTemplate amqpTemplate;

    @PostMapping(value = "/queue/{name}")
    public Mono<ResponseEntity<?>> sendMessageToQueue(
      @PathVariable String name, @RequestBody String payload) {

        DestinationInfo d = destinationsConfig
          .getQueues().get(name);
        if (d == null) {
            return Mono.just(
              ResponseEntity.notFound().build());
        }

        return Mono.fromCallable(() -> {
            amqpTemplate.convertAndSend(
              d.getExchange(),
              d.getRoutingKey(),
              payload);
            return ResponseEntity.accepted().build();
        });
    }

@Component
public class MessageListenerContainerFactory {

    @Autowired
    private ConnectionFactory connectionFactory;

    public MessageListenerContainerFactory() {}

    public MessageListenerContainer createMessageListenerContainer(String queueName) {
        SimpleMessageListenerContainer mlc = new SimpleMessageListenerContainer(connectionFactory);
        mlc.addQueueNames(queueName);
        return mlc;
    }
}

@Autowired
private MessageListenerContainerFactory messageListenerContainerFactory;

@GetMapping(
  value = "/queue/{name}",
  produces = MediaType.TEXT__EVENT__STREAM__VALUE)
public Flux<?> receiveMessagesFromQueue(@PathVariable String name) {

    DestinationInfo d = destinationsConfig
      .getQueues()
      .get(name);
    if (d == null) {
        return Flux.just(ResponseEntity.notFound()
          .build());
    }

    MessageListenerContainer mlc = messageListenerContainerFactory
      .createMessageListenerContainer(d.getRoutingKey());

    Flux<String> f = Flux.<String> create(emitter -> {
        mlc.setupMessageListener((MessageListener) m -> {
            String payload = new String(m.getBody());
            emitter.next(payload);
        });
        emitter.onRequest(v -> {
            mlc.start();
        });
        emitter.onDispose(() -> {
            mlc.stop();
        });
      });

    return Flux.interval(Duration.ofSeconds(5))
      .map(v -> "No news is good news")
      .mergeWith(f);
}

spring:
  rabbitmq:
    host: localhost
    port: 5672
    username: guest
    password: guest

destinations:
  queues:
    NYSE:
      exchange: nyse
      routing-key: NYSE

$ curl -v -d "Test message" http://localhost:8080/queue/NYSE
**  timeout on name lookup is not supported
**    Trying 127.0.0.1...
**  Connected to localhost (127.0.0.1) port 8080 (#0)
> POST/queue/NYSE HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.49.1
> Accept: ** /**
> Content-Length: 12
> Content-Type: application/x-www-form-urlencoded
>
**  upload completely sent off: 12 out of 12 bytes
< HTTP/1.1 202 Accepted
< content-length: 0
<
**  Connection #0 to host localhost left intact

$ docker exec rabbitmq rabbitmqctl list__queues
Timeout: 60.0 seconds ...
Listing queues for vhost/...
NYSE    1

$ curl -v http://localhost:8080/queue/NYSE
**  timeout on name lookup is not supported
**    Trying 127.0.0.1...
**  Connected to localhost (127.0.0.1) port 8080 (#0)
> GET/queue/NYSE HTTP/1.1
> Host: localhost:8080
> User-Agent: curl/7.49.1
> Accept: ** /**
>
< HTTP/1.1 200 OK
< transfer-encoding: chunked
< Content-Type: text/event-stream;charset=UTF-8
<
data:Test message

data:No news is good news...

... same message repeating every 5 secs

Timeout: 60.0 seconds ...
Listing queues for vhost/...
NYSE    0

@PostConstruct
public void setupTopicDestinations(
    destinationsConfig.getTopics()
      .forEach((key, destination) -> {
          Exchange ex = ExchangeBuilder
            .topicExchange(destination.getExchange())
            .durable(true)
            .build();
            amqpAdmin.declareExchange(ex);
      });
}

@PostMapping(value = "/topic/{name}")
public Mono<ResponseEntity<?>> sendMessageToTopic(
  @PathVariable String name, @RequestBody String payload) {

    DestinationInfo d = destinationsConfig
      .getTopics()
      .get(name);

    if (d == null) {
        return Mono.just(ResponseEntity.notFound().build());
    }

   return Mono.fromCallable(() -> {
       amqpTemplate.convertAndSend(
         d.getExchange(), d.getRoutingKey(),payload);
            return ResponseEntity.accepted().build();
        });
    }

@GetMapping(
  value = "/topic/{name}",
  produces = MediaType.TEXT__EVENT__STREAM__VALUE)
public Flux<?> receiveMessagesFromTopic(@PathVariable String name) {
    DestinationInfo d = destinationsConfig.getTopics()
        .get(name);
    if (d == null) {
        return Flux.just(ResponseEntity.notFound()
            .build());
    }
    Queue topicQueue = createTopicQueue(d);
    String qname = topicQueue.getName();
    MessageListenerContainer mlc = messageListenerContainerFactory.createMessageListenerContainer(qname);
    Flux<String> f = Flux.<String> create(emitter -> {
        mlc.setupMessageListener((MessageListener) m -> {
            String payload = new String(m.getBody());
            emitter.next(payload);
        });
        emitter.onRequest(v -> {
            mlc.start();
        });
        emitter.onDispose(() -> {
            amqpAdmin.deleteQueue(qname);
            mlc.stop();
        });
      });

    return Flux.interval(Duration.ofSeconds(5))
        .map(v -> "No news is good news")
        .mergeWith(f);
}

private Queue createTopicQueue(DestinationInfo destination) {

    Exchange ex = ExchangeBuilder
      .topicExchange(destination.getExchange())
      .durable(true)
      .build();
    amqpAdmin.declareExchange(ex);
    Queue q = QueueBuilder
      .nonDurable()
      .build();
    amqpAdmin.declareQueue(q);
    Binding b = BindingBuilder.bind(q)
      .to(ex)
      .with(destination.getRoutingKey())
      .noargs();
    amqpAdmin.declareBinding(b);
    return q;
}

destinations:
## ... queue destinations omitted
  topics:
    weather:
      exchange: alerts
      routing-key: WEATHER

$ docker exec docker__rabbitmq__1 rabbitmqctl list__exchanges
Listing exchanges for vhost/...
amq.topic       topic
amq.fanout      fanout
amq.match       headers
amq.headers     headers
        direct
amq.rabbitmq.trace      topic
amq.direct      direct
alerts  topic

$ docker exec rabbitmq rabbitmqctl list__bindings
Listing bindings for vhost/...
        exchange        NYSE    queue   NYSE   []nyse    exchange        NYSE    queue   NYSE   []----

2つのコマンドシェルを開き、それぞれに対して次のコマンドを発行して、宛先にサブスクライブする2、3のサブスクライバを開始しましょう。

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