feat: System wide typed pub sub topic registry #32262
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Something I've thought about during the weekend: There is a race between TTL shutdown and the janitor actor cleaning up, we could potentially do better by having an I'm-going-to-stop callback to the Topic that it calls just before shutting down and then have a retry spin if the name is still occupied but not in the registry where the actor will soon shut down. Not entirely sure it is worth it though. |
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I think there are several other uncertainties with delivery via PubSub so it's ok with possible loss in that unlucky moment. |
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One race that I think would be good to address is the first publish race. I think, when you first publish to a topic that is inactive, there's a race between the message you send, and the first listing sent by the receptionist, and I'm pretty sure the message you send will nearly always win, so that means that first message sent to a topic that is inactive on the node, but has subscribers elsewhere in the cluster, will almost never make it to the subscribers. If we could stash publish messages until the first listing is received (since the first listing is always sent immediately as an acknowledgement of subscribing), I think that would solve it. |
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We already have that in the typed group topic, so I think we can do that, but let's treat it as a separate issue. I created #32267 for that. |
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akka-actor-typed/src/main/scala/akka/actor/typed/pubsub/PubSub.scala
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| The identity of the topic is a tuple of the type of messages that can be published and a string topic name but it is recommended | ||
| to not define multiple topics with different types and the same topic name. | ||
| Topics can be looked up in the @apidoc[PubSub](akka.actor.typed.pubsub.PubSub$) registry, this way the same topic will be represented by the same actor for a whole | ||
| actor system. If the topic has not yet been started. |
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Is that last sentence incomplete?
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Yea, halfway through a thought. Fixed now.
akka-actor-typed/src/main/scala/akka/actor/typed/pubsub/PubSub.scala
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….scala Co-authored-by: Renato Cavalcanti <renato@cavalcanti.be>
On top of #32261
References #31053