Add ability to change the exchange type on producer about op-rabbit HOT 4 CLOSED

Hi @slevine - this is certainly possible. But, can you help me understand a little more about your use case? Why do you feel like this is important?

The Publisher class is not declared as final, so you could extend it that way.

class DeclaringPublisher(routingKey: String, topicBinding: TopicBinding) extends Publisher(topicBinding.exchange.exchangeName, routingKey) {
  private var declared: Boolean = false
  override def apply(c: Channel, data: Array[Byte], properties: BasicProperties): Unit = {
    if (! declared) synchronized {
      if ( ! declared ) {
        topicBinding.declare(c)
        declared = true
      }
    }
    super.apply(c, data, properties)
  }
}

Then:

val declaringPublisher = DeclaringPublisher("my.topic", TopicBinding(...))
Message(declaringPublisher, data)

Another option, if you want to just declare the topic, but not send a message:

class EagerDeclare(definition: QueueDefinition) extends MessageForPublicationLike {
  private val _declared: Promise[Unit]
  val declared = _applied.future
  def apply(c: Channel): Unit =
    _declared.complete(Try(definition.declare(c)))
}

val declaration = EagerDeclare(TopicBinding(...))
rabbitControl ! declaration
declaration.declared.foreach { _ =>
  // ready for action
}

Both of these are kind of hacks, granted. If I can learn more about what your problem is, we can come up with a better solution and perhaps get it implemented before the RC label comes off.

from op-rabbit.

Thanks for the quick reply @timcharper -- really appreciate it. The main reason it is important to us is because we are not using standard exchange types, and some of the time, the producer will bind before the consumer, so we needed a mechanism to change the ex type when the producer binds.

from op-rabbit.

Okay, the obvious solution here would be to allow you to pass a QueueDefinition or an ExchangeDefinition to your message publisher, and having said definition lazily apply.

Do you think that will solve it well enough, or can you think of a more enlightened way to solve it?

from op-rabbit.

@slevine please see v1.0.0-RC4, which should support the case you need. There was an already implemented feature that was somewhat similar to it, so I made the solution more general to apply to yours, also.

From The Upgrading Wiki Page:

val factory = Message.factory(
  Publisher.queue(
    Queue("ahora-existe")))

val factory = Message.factory(
  Publisher.exchange(
    Binding.topic(
      Queue("ahora-existe", topics = List("los.nachos.*")))))

from op-rabbit.