eventual

Server-Sent Event and EventSource helpers for core.async.

Installation

To use eventual, add the following to your :dependencies:

[com.ninjudd/eventual "0.5.0"]

Server

To create a handler that returns a stream of Server-Sent Events, you need use ring-async or some other servlet adapter that supports asynchronous responses by returning a core.async channel for body.

(ns server-events-sample
  (:require [clojure.core.async :refer [go >! chan close!]]
            [ninjudd.eventual.server :refer [edn-events]]
            [ring.adapter.jetty-async :refer [run-jetty-async]]))

(defn sse-handler [request]
  (let [events (chan)]
    (go (loop [...]
          (if ...
            (>! events event)
            (recur ...)))
        (close! events))
    (edn-events events)))

(defn start []
  (run-jetty-async sse-handler {:join? false :port 8000}))

Client

To connect to a server endpoint that returns an event stream in ClojureScript, eventual provides a helper function that returns a core.async channel but user EventSource behind the scenes.

(ns client-events-sample
  (:require [cljs.core.async :refer [<!]]
            [ninjudd.eventual.client :refer [edn-events]])
  (:require-macros [cljs.core.async.macros :refer [go]]))

(let [events (edn-events "http://.../events")]
  (go (loop [...]
        (if-let [event (<! events)]
          ...
          (recur ...)))))

Event Metadata

By default, only message events are sent and received. However, you can send diffent event types by providing metadata on the events you put onto the channel. You can also provide an event id this way.

(go ...
  (>! events (with-meta event {:event-type :add, :event-id 1234})))

To receive events besides message on the client, you have to provide a list of events you handle. Events taken from the channel will have metadata with their type and id.

(edn-events "http://.../events" [:add :remove])

License

Copyright © 2015 Justin Balthrop

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version.