clojure.core.async: how to deal with deadlocks

Perhaps I should post some code snippets and tips on this blog? Much of this will probably be obvious and simple, but it's stuff I sometimes forget.

clojure.core.async: how to deal with deadlocks:

	;;; https://www.Quanto.ga
	;; clojure.core.async: how to deal with deadlocks
	;;
	;; If you have a channel that in the "reader" or consumer also sends
	;; to itself you might end up with a deadlock in certain cases. Especially
	;; if you don't want to use buffered channels -- perhaps because it is
	;; impossible to predict how much of a buffer you will need:
	(let [ch (async/chan)
	f (future
	(dotimes [i 3]
	(println "ch:" (async/<!! ch))
	(async/>!! ch i))
	(println "ch (last one): " (async/<!! ch)))]
	(try
	(async/>!! ch -1)
	(Thread/sleep 500)
	(finally
	(future-cancel f)))
	(println "...done"))
	;; ch: -1
	;; ...done
	;; By using async/go or async/thread you can deal with this:
	(let [ch (async/chan)
	f (future
	(dotimes [i 3]
	(println "ch:" (async/<!! ch))
	(async/go (async/>! ch i))) ;; or (async/thread (async/>!! ch i))
	(println "ch (last one): " (async/<!! ch)))]
	(try
	(async/>!! ch -1)
	(Thread/sleep 500)
	(finally
	(future-cancel f)))
	(println "...done"))
	;; ch: -1
	;; ch: 0
	;;ch: 1
	;; ch (last one): 2
	;;...done
	;; Of course one could also use buffering in this case,
	;; but this changes the properties of your system in a different way.

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