jet

Jet is a jetty9 server + client library for clojure. It's a drop in adapter replacement for ring apps.

What's in the box?

• ring adapter running on jetty9

• Ring extension where core.async channel as response toggle Jetty9 Async

• Ring extension where core.async channel as :body in response does Chunked Transfers

• Websocket Server with a simple yet powerful api based on core.async

• WebSocket Client sharing the same principles/api than the WebSocket server handlers

• Asynchronous HTTP Client with streaming support

The server part started from the code of the various ring-jetty9-adapters out there.

The API is still subject to changes.

Documentation

codox generated documentation.

Installation

jet is available on Clojars.

Add this to your dependencies:

[cc.qbits/jet "0.6.4"]

Examples

Vanilla Ring handler

Nearly the same as any ring compliant adapter

(use 'qbits.jet.server)

(run-jetty {:ring-handler handler :port ...})

Ring Async

You can have fine control over Jetty9 Async mode using a core.async channel as response:

(require '[clojure.core.async :as async])

(defn async-handler [request]
  (let [ch (async/chan)]
    (async/go
      (async/<! (async/timeout 1000))
      (async/>! ch
                {:body "foo"
                 :headers {"Content-Type" "foo"}
                 :status 202}))
    ch))

(qbits.jet.server/run-jetty {:ring-handler async-handler})

Server Chunked Responses

If you return a core.async channel in a ring body jetty will go into async mode and the channel values will be streamed as chunks. If the channel is closed the connection ends. If an error occurs or the client disconnects the channel closes as well.

(require '[clojure.core.async :as async])

(defn handler
  [request]
  (let [ch (async/chan 1)]
    (async/go
     (dotimes [i 5]
       (async/<! (async/timeout 300))
       (async/>! ch (str i "\n")))
     (async/close! ch))
    {:body ch
     :headers {"Content-Type" "prout"}
     :status 201}))

(qbits.jet.server/run-jetty {:ring-handler handler :port ...})

WebSocket

In the options the :websocket-handler is the root handler for all websocket connections.

The websocket handlers receive a ring request map + 3 core.async channels and the underlying WebSocketAdapter instance for potential advanced uses.

• ctrl will receive status messages such as [::error e] [::close reason]

• in will receive content sent by this connected client

• out will allow you to push content to this connected client and close the socket

An example with a little PING/PONG between client and server:

(use 'qbits.jet.server)

;; Simple ping/pong server, will wait for PING, reply PONG and close connection
(run-jetty
  {:port 8013
   :websocket-handler
    (fn [{:keys [in out ctrl ws]
          :as opts}]
        (async/go
          (when (= "PING" (async/<! in))
            (async/>! out "PONG")
            (async/close! out))))}})

The websocket client is used the same way

(use 'qbits.jet.client.websocket)

;; Simple PING client to our server, sends PING, waits for PONG and
;; closes the connection
(connect! "ws://localhost:8013/"
          (fn [{:keys [in out ctrl ws]}]
            (async/go
              (async/>! out "PING")
              (when (= "PONG" (async/<! in))
                (async/close! out))))))

If you close the :out channel, the socket will be closed, this is true for both client/server modes.

HTTP Client

The API is nearly identical to clj-http and other clients for clojure. One of the major difference is that calls to the client return a channel that will receive the eventual response asynchronously. The response is then a fairly standard ring response map, except the body, which is also a core.async channel (support for chunked responses).

Another major difference is that Jetty enforces client reuse (browser model). Calls to http client functions require a "client" argument, that can/would be shared by your app depending on context. This has a few advantages (shared cookie/auth conf, pooling etc). To quote the Jetty9 documentation:

HttpClient provides an efficient, asynchronous, non-blocking implementation to perform HTTP requests to a server through a simple API that offers also blocking semantic.

HttpClient provides easy-to-use methods such as GET(String) that allow to perform HTTP requests in a one-liner, but also gives the ability to fine tune the configuration of requests via newRequest(URI).

HttpClient acts as a central configuration point for network parameters (such as idle timeouts) and HTTP parameters (such as whether to follow redirects).

HttpClient transparently pools connections to servers, but allows direct control of connections for cases where this is needed.

HttpClient also acts as a central configuration point for cookies, via getCookieStore().

See the docs for details, HTTP client API docs qbits.jet.client.http/request & qbits.jet.client.http/client (the former builds on the later).

(use 'qbits.jet.client.http)
(use 'clojure.core.async)

(def cl (client))

;; returns a chan
(http/get cl "http://graph.facebook.com/zuck")
user> #<ManyToManyChannel clojure.core.async.impl.channels.ManyToManyChannel@731db933>

;; block for the response
(<!! (http/get cl "http://graph.facebook.com/zuck"))

user> {:status 200,
       :headers
       {"content-type" "text/javascript; charset=UTF-8",
        "access-control-allow-origin" "*",
        "content-length" "173",
        "x-fb-debug"
        "jkc4w5S1VN3bLddmGEU+r3F/5ANxPZXrcqq3bUXJ3n2bwZq7WB0xy+mB/CziD56wHWd2us//p2dTmRQSIiW+Yg==",
        "facebook-api-version" "v1.0",
        "connection" "keep-alive",
        "pragma" "no-cache",
        "expires" "Sat, 01 Jan 2000 00:00:00 GMT",
        "x-fb-rev" "1358170",
        "etag" "\"3becf5f2bb7ec39daa6bb65345d40b9f4b1db483\"",
        "date" "Wed, 06 Aug 2014 15:51:02 GMT",
        "cache-control" "private, no-cache, no-store, must-revalidate"},
       :body
       #<ManyToManyChannel clojure.core.async.impl.channels.ManyToManyChannel@7ca698b0>}


;; get to the body
(-> (http/get cl "http://graph.facebook.com/zuck")
    <!!
    :body
    <!!)
user> "{\"id\":\"4\",\"first_name\":\"Mark\",\"gender\":\"male\",\"last_name\":\"Zuckerberg\",\"link\":\"https:\\/\\/www.facebook.com\\/zuck\",\"locale\":\"en_US\",\"name\":\"Mark Zuckerberg\",\"username\":\"zuck\"}"

;; autodecode the body
(-> (get cl "http://graph.facebook.com/zuck" {:as :json})
         async/<!!
         :body
         async/<!!)
user> {:id "4",
       :first_name "Mark",
       :gender "male",
       :last_name "Zuckerberg",
       :link "https://www.facebook.com/zuck",
       :locale "en_US",
       :name "Mark Zuckerberg",
       :username "zuck"}

;; POST
(post cl "http://foo.com" {:form-params {:foo "bar" :baz 1}})

And you can imagine (or read the api doc) how post, put, delete and other methods work. It's fairly standard. All the "method" functions are just api sugar around qbits.jet.client.http/request.

Please check the Changelog if you are upgrading.

License

Copyright © 2014 Max Penet

Distributed under the Eclipse Public License, the same as Clojure.