Eh, you're right, there is however, a blocking version of go, called thread:
So perhaps something like this?
(thread
(while true
(let [[filename response-chan] (<!! c)]
(>!! response-chan (slurp filename)))))
Or perhaps I'm missing something.
Timothy
On Mon, Jul 8, 2013 at 10:09 AM, vemv <[email protected]> wrote:
> Took me a while to get the idea but higher-order channels are brilliant -
> that way one ensures a given reply was actually targeted at one's request.
> Thanks for the suggestion!
>
> Faux-agents would have the limitation of not being to (reasonably) perform
> blocking I/O - which is the point of my sample program.
>
> An improved version:
>
> (require '[clojure.core.async :as async :refer :all])
> (import '[java.util.concurrent Executors]
> '[java.util.concurrent.locks ReentrantReadWriteLock])
>
>
> (spit "bar" (apply str (shuffle (range 100))))
>
> (def max-concurrency 4)
>
> (def requests (chan max-concurrency))
>
> ;; only ensures exclusive access within the app - not across the OS
> ;; too lazy to use a FileLock :)
> (def lock (ReentrantReadWriteLock.))
>
> (def rw-pool (Executors/newFixedThreadPool max-concurrency))
>
> ;; one sends actions to anonymous one-off multiple agents
> ;; (as opposed to a single, named one), in order to increase concurrency
>
> (dotimes [_ max-concurrency]
> (go (loop []
> (when-let [request (<! requests)]
> (send-via rw-pool (agent nil) (fn [_]
> (try
> (-> lock .readLock .lock)
> (>!! request (seq (slurp
> "bar")))
> (finally
> (-> lock .readLock
> .unlock)))))
> (recur)))))
>
> (go (loop []
> (let [request (chan)
> _ (>! requests request)
> response (<! request)]
> (send-via rw-pool (agent nil) (fn [_]
> (try
> (-> lock .writeLock .lock)
> (spit "bar" (apply str (shuffle
> response)))
> (finally
> (-> lock .writeLock
> .unlock)))))
> (recur))))
>
> As commented, locking is only partially useful (that's why opening the
> file might display an empty string at times). Also, don't know what would
> be the best way to indicate termination to the second go block...
>
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--
“One of the main causes of the fall of the Roman Empire was that–lacking
zero–they had no way to indicate successful termination of their C
programs.”
(Robert Firth)
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