Asynchronous processes and cancellation

gistfile1.clj

(defn exec-cancellable
  [cmd cancel]
  (let [proc (sh/proc "sh" "-c" cmd)
        exit (go (sh/exit-code proc))
        [result ch] (alts!! [cancel exit])]
    (go (if (= ch cancel)
          (do
            (sh/destroy proc)
            :cancelled)
          (if (zero? result) :success :failure)))))

(defn exec-group
  [cmds]
  (let [cancel (async/chan)
        f #(exec-cancellable % cancel)
        ch (async/merge (map f cmds))]
    (loop [result true]
      (let [val (<!! ch)]
        (cond
          (nil? val) result
          (= val :failure) (do
                             (async/close! cancel)
                             (recur false))
          :else (recur result))))))