Executing a function with a timeout

Question

What would be an idiomatic way of executing a function within a time limit? Something like,

(with-timeout 5000
 (do-somthing))

Unless do-something returns within 5000 throw an exception or return nil.

EDIT: before someone points it out there is,

clojure (with-timeout ... macro)

but with that the future keeps executing that does not work in my case.

Answer 1

I think you can do this reasonably reliably by using the timeout capability within futures:

  (defmacro with-timeout [millis & body]
    `(let [future# (future ~@body)]
      (try
        (.get future# ~millis java.util.concurrent.TimeUnit/MILLISECONDS)
        (catch java.util.concurrent.TimeoutException x# 
          (do
            (future-cancel future#)
            nil)))))

A bit of experimenting verified that you need to do a future-cancel to stop the future thread from continuing to execute....

Answer 2

What about?

    (defn timeout [timeout-ms callback]
     (let [fut (future (callback))
           ret (deref fut timeout-ms ::timed-out)]
       (when (= ret ::timed-out)
         (future-cancel fut))
       ret))

    (timeout 100 #(Thread/sleep 1000))

    ;=> :user/timed-out