Pedestal 0.3.0 example with SSE

service.clj

;; In Pedestal 0.3.1, you won't have to use an atom.
;;   You'll pass the channel into the SSE creation function (instead of it passing one back to you)
(def event-ch (atom nil))

(defn home-page                                                                                                                                       
  [request]                                                                                                                                           
  (ring-resp/response "Hello World!"))

(defroutes routes
  [[["/" {:get home-page}
    ;; Set default route-oriented interceptors
    ^:interceptors [(body-params/body-params)
                    bootstrap/html-body
                    timing-interceptor]
    ["/about" {:get about-page}]
    ["/user/:user" {:get greet-user}]
    ["/echo" {:get echo-page}]
    ;; If you dig way down in the Pedestal code, you'll find that the new SSE
    ;;  sets the context's body to a channel, which you can then use to control/interact with events
    ["/events" {:get [::events (sse/start-event-stream (fn [{:keys [body] :as context}] 
                                                         (reset! event-ch body)))]}]                                                                  
    ["/json" ^:interceptors [bootstrap/json-body]
      ["/hello" {:get [::json-hello (fn [req]
                                      (ring-resp/response {:response "Hello, World"}))]}]]]]])