detecting dropped items with core.async pub

Question

I'm looking at using a shared core.async pub channel as the primary communication layer for my app as a way to introduce some indirection between components. I'm concerned about the behavior of pub, though, specifically the way that it silently drops items if there is no matching sub for a given topic. In a large system, this seems like it could be a real headache to debug. Is there any way to detect that an item got dropped, or at least to throw an exception in this case?

@AlejandroC. in order to enable routing messages to different components based on topic, and to enable multiple subscribers for the same message. — Derek Thurn
Provide a fallback topic (:default) in the topic-fn and always register a default sub handling that topic? — glts
@glts , how would you know when to return the :default topic from topic-fn? — Derek Thurn

Alejandro C. Alejandro C. · Accepted Answer · 2017-06-09T18:27:15

No, it looks like it just gets dropped silently if there's no matching topic subscriber https://github.com/clojure/core.async/blob/2afc2dc5102f60713135ffca6fab993fb35809f0/src/main/clojure/clojure/core/async.clj#L879

detecting dropped items with core.async pub

1 Answers