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;;
;; 来自Dennis http://blog.fnil.net/blog/964a2d5c851b7e5fd65b630a7ef96966/
;; 
;; 更多使用场景： 在用户首页登陆后的各种统计信息， 尽量用并发去DB查询， 避免串行查询。 
;; 比如： 用户代办信息; 站内信息; 
;;

(defn add-app-info
  "添加应用统计信息。"
  [app]
  (assoc app
         :yesterday_reqs (count-reqs app 7)
         :monthly_reqs (count-reqs app 30)
         :total_users (count-users app)))

(defn get-client-apps
  "获取用户的应用列表"
  [client_id]
  (->> client_id
       (db/find-apps-by-client-id)
       (map add-app-info)))

;; 改造获取用户的应用列表
;; 将add-app-info的串行执行改为并行执行
(defn get-client-apps
  "获取用户的应用列表"
  [client_id]
  (->> client_id
       (db/find-apps-by-client-id)
       (pmap add-app-info)))
       
       
       

;;
;; pcall execute bigtask
;;
(ns alexcoding.bf.pcalldemo)

(defn bigtask [name]
  (Thread/sleep 5000)
  name
  )

(comment
  (pcalls #(bigtask "alex") #(bigtask "kate")))

;; from stackeroverflow.
(defn sleeper [s thing]
  (Thread/sleep (* 1000 s))
  thing)

(def actions [#(sleeper 2 :1st) #(sleeper 3 :2nd) #(keyword "3rd")])

(comment
  (apply pcalls actions))

;; 
;; pcall的底层是通过pmap实现的
;;
(defn pcalls
  "Executes the no-arg fns in parallel, returning a lazy sequence of
  their values"
  {:added "1.0"
   :static true}
  [& fns] (pmap #(%) fns))