clojure (with-timeout … macro)

Question

I\'m looking for a macro that will throw an exception if an expression takes longer than X seconds to complete.

Answer 1

I came across this thread recently while asking the same question. I wasn't completely satisfied with the answers given so I cobbled together an alternative solution. This solution will run your code in the current thread and spin of a future to interrupt it after a set timeout in ms.

(defn invoke-timeout [f timeout-ms]
  (let [thr (Thread/currentThread)
        fut (future (Thread/sleep timeout-ms)
                    (.interrupt thr))]
    (try (f)
         (catch InterruptedException e
           (throw (TimeoutException. "Execution timed out!")))
         (finally
           (future-cancel fut)))))

(defmacro timeout [ms & body] `(invoke-timeout (fn [] ~@body) ~ms))

You would use it in your code like this:

(timeout 1000 your-code)

OR

(invoke-timeout #(your-code) 1000)

One caveat to keep in mind is that your-code must not catch the InterruptedException used to trigger the TimeoutException. I use this for testing and it works well.

See the Thread.interrupt() javadoc for additional caveats.

You can see this code in use here.