Aleph is a Clojure framework for asynchronous communication, built on top of Netty and Lamina.
Aleph allows the creation of both clients and servers that can communicate using an array of protocols (HTTP, WebSockets, TCP, UDP, and others), and represents that communication via a single abstraction, channels. Thanks to the underlying libraries and the event-driven approach to communication, these clients and servers can be highly scalable.
In the project.clj file at the top level of your project, add Aleph as a dependency:
(defproject my-project "1.0.0"
:dependencies [[org.clojure/clojure "1.5.0"]
[aleph "0.3.0-beta15"]])Aleph conforms to the interface described by Ring, with one small difference: the request and response are decoupled.
(use 'lamina.core 'aleph.http)
(defn hello-world [channel request]
(enqueue channel
{:status 200
:headers {"content-type" "text/html"}
:body "Hello World!"}))
(start-http-server hello-world {:port 8008})For more on HTTP functionality, read the wiki.
This snippet prints out a never-ending sequence of tweets:
(use 'lamina.core 'aleph.http 'aleph.formats)
(let [ch (:body
(sync-http-request
{:method :get
:basic-auth ["aleph_example" "_password"]
:url "https://stream.twitter.com/1/statuses/sample.json"
:delimiters ["\r"]}))]
(doseq [tweet (map decode-json (lazy-channel-seq ch))]
(prn tweet)))A more in-depth exploration of this example can be found here.
Making a simple chat client is trivial. In this, we assume that the first message sent by the client is the user's name:
(use 'lamina.core 'aleph.http)
(def broadcast-channel (channel))
(defn chat-handler [ch handshake]
(receive ch
(fn [name]
(siphon (map* #(str name ": " %) ch) broadcast-channel)
(siphon broadcast-channel ch))))
(start-http-server chat-handler {:port 8008 :websocket true})Here is a basic echo server:
(use 'lamina.core 'aleph.tcp)
(defn echo-handler [channel client-info]
(siphon channel channel))
(start-tcp-server echo-handler {:port 1234})For more on TCP functionality, visit the wiki.
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Other protocols are supported, and still more are forthcoming.
For more information, visit the wiki or the API documentation. If you have questions, please visit the mailing list.
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