fetcher.clj

(ns fetcher
  (:require [clojure.tools.logging :as log]))

(def completed? (promise))

(def status (atom 0))

(defmacro make-worker [& forms]
  `(do
     (swap! status inc)
     (try
       (do ~@forms)
       (catch Throwable e# (log/info "Error" e#)))
     (swap! status dec)))

(defn make-request [url]
  (log/info "calling " url)
  (when (re-find #"yahoo" url)
    (throw (Exception. (str "b00m on" url))))
  (Thread/sleep 1000))

(def urls ["http://google.com"
           "http://www.roomkey.com"
           "http://yahoo.com"])

(def work (map (fn [url]
                 (fn []
                   (make-worker (make-request url)))) urls))

(add-watch status :done? (fn [_ _ o n] (when (= n 0) (deliver completed? true))))

(log/info "starting...")
(doseq [w work]
  (future (w)))
@completed?
(log/info "done")