Two Brokers same Broker Type - Emit to external Broker

App 1 has only connection to Broker 1, which is considered the app domain for this app. This is the same as the Single Broker scenario.

App 3 has only connection to Broker 2, which is considered the app domain for this app. This is the same as the Single Broker scenario.

App 2 has two brokers, Broker 1 and Broker 2. Broker 1 is considered the app domain for this app, and Broker 2 is considered an external broker which will be called accounts domain for this scenario.

So you need to configure the connection properties for each broker.

In this scenario, Broker 1 is considered the app domain by default, so App 2 can listen and send all operations from/to this broker, but it can only publish commands and queries to Broker 2 and listen for events from the Broker 2 (accounts domain).

Note: App 2 cannot listen notification events, cannot listen for queries, and commands from Broker 2. This is for responsibility segregation.

To send commands and queries to Broker 2 you need to use the DirectAsyncGateway interface with the accounts domain , and the same when listen, you should pass the domain name.

Listen from external domain

@Bean
@Primary
public HandlerRegistry handlerRegistrySubs(UseCase useCase) {
    return HandlerRegistry.register()
            //.serveQuery(...)
            //.handleCommand(...)
            //.listenEvent(...)
            //.listenNotificationEvent(...)
            .listenDomainEvent("accounts", "event-name", handler::process, MyEventData.class)
            .listenDomainCloudEvent("accounts", "event-name", handler::processCloudEvent);
}

Send to external domain

@Service
@RequiredArgsConstructor
public class SampleRestController {
    private final DirectAsyncGateway directAsyncGateway;

    public Mono<Teams> getTeams() {
        AsyncQuery<Request> query = ....
        return directAsyncGateway.requestReply(query, "external-service", Teams.class, "accounts");
    }

    public Mono<Teams> getTeamsCloudEvent() {
        CloudEvent query = ....
        return directAsyncGateway.requestReply(query, "external-service", CloudEvent.class, "accounts")
                .map(...);
    }
}

Next are configurations needed to set up this scenario for App 2.

RabbitMQ

App 2 needs two domains: app for Broker 1 and accounts for Broker 2, each with its own connection properties. See RabbitMQ Configuration for the full list of properties, and the Approach 2 section for loading connection credentials from a secrets manager instead of YAML.

application.yaml

app:
  async:
    app: # this is the name of the default domain, connected to Broker 1
      connectionProperties:
        host: localhost
        port: 5672
        username: guest
        password: guest
        virtual-host: /
    # Another domain can be configured with the same properties structure as app
    accounts: # this is a second domain name, connected to Broker 2
      connectionProperties:
        host: localhost
        port: 5673
        username: guest
        password: guest
        virtual-host: /accounts

Kafka

App 2 needs two domains: app for Broker 1 and accounts for Broker 2, each with its own connection properties. See Kafka Configuration for the full list of properties, and the Approach 2 section for loading connection credentials from a secrets manager instead of YAML.

application.yaml

reactive:
  commons:
    kafka:
      app: # this is the name of the default domain, connected to Broker 1
        connectionProperties:
          bootstrap-servers: localhost:9092
      # Another domain can be configured with the same properties structure as app
      accounts: # this is a second domain name, connected to Broker 2
        connectionProperties:
          bootstrap-servers: localhost:9093