hystrix clj snippets

hystrix-clj-snippets.clj

(def user-prefs
  {:type          :command
   :group-key     :Cassandra
   :command-key   :GetUserPreferences
   :run-fn        (fn [user-id] ... do request ...)
   :fallback-fn   (fn [user-id] { ... default prefs ...})
   :cache-key-fn  (fn [user-id] (str user-id)) })

(require '[com.netflix.hystrix.core :as hystrix])

; Execute
(-> user-prefs
    hystrix/command ; normalize
    (hystrix/execute 123456))
;=> {... user prefs ...}

; Queue Future
(-> user-prefs
    hystrix/command
    (hystrix/queue 123456))
;=> Future<{... user prefs ...}>

; Rx Observable
(-> user-prefs
    hystrix/command
    (hystrix/observe 123456))
;=> rx.Observable<{... user prefs ...}>


Reduce Boilerplate with a macro

(defn user-prefs
  [user-id]
  ... do request ...)

(user-prefs 123456)
;=> {... user prefs ...}



(hystrix/defcommand user-prefs
  [user-id]
  ... do request ...)

(user-prefs 123456)
;=> {... user prefs ...}

(hystrix/queue #'user-prefs 123456)
;=> Future<{... user prefs ...}>

(hystrix/observe #'user-prefs 123456)
;=> rx.Observable<{... user prefs ...}>



(hystrix/defcommand user-prefs
  {:hystrix/group-key     :Cassandra
   :hystrix/command-key   :GetUserPreferences
   :hystrix/fallback-fn   (fn [user-id] { ... default prefs ...})
   :hystrix/cache-key-fn  (fn [user-id] (str user-id)) }
  [user-id]
  ... do request ...)




(hystrix/defcommand user-prefs
  {:hystrix/init-fn (fn [_ ^HystrixComand$Setter setter]
                      ... customize setter ...)}
  [user-id]
  ... do request ...)



(let [^HystrixCommand e (hystrix/instantiate #'user-prefs 123456)]
  ... do something with raw HystrixCommand ...)


(hystrix/defcommand enrich-videos
  [videos]
  (for [v videos]
    (get-title v)))

(binding [*out* my-writer]
  (printing-command))