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websockets with core.async and http-kit
(defn build-routes
[{:keys [bus queues] :as app-data}]
(routes
(GET "/data" req
; get an http-kit websocket channel for this request
(http/with-channel req req-ch
; make a channel for subscriptions to the data updated event bus
(let [metrics (async/chan)]
; subscribed to all messages in the updated topic
(async/sub bus :updated metrics)
; when the http-kit channel closes, also close the event bus subscription
(http/on-close req-ch (partial async/close! metrics))
; loop in a go-routine
(async/go-loop []
; read (<!!) will block until there is a message to read
(async/<!! metrics)
; send whatever is the current state of app-data down the channel
(http/send! req-ch (json/write-str @queues))
; only loop if the websocket channel is still open
(when (http/open? req-ch) (recur))))))
(route/resources "/")
(route/not-found "Not Found")))
(defrecord AppRoutes []
component/Lifecycle
(start [this]
(assoc this
:routes (build-routes (:data this))))
(stop [this] this))
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