使用Clojure进行服务器编程

如何在Clojure中实现10k连接echo服务器？

clojure.contrib.server-socket不是答案,因为它为每个连接创建一个新的OS线程.

关于Clojure的好处是你拥有像netty这样的JVM所有这些优秀的库,它们经过高度优化,可配置和深思熟虑.这样的事情会让你前进:

(ns netty
  (:gen-class)
  (:import
     [java.net InetSocketAddress]
     [java.util.concurrent Executors]
     [org.jboss.netty.bootstrap ServerBootstrap]
     [org.jboss.netty.channel Channels ChannelPipelineFactory
                              SimpleChannelHandler]
     [org.jboss.netty.channel.socket.nio NioServerSocketChannelFactory]
     [org.jboss.netty.buffer ChannelBuffers]))

(declare make-handler)

(defn start
  "Start a Netty server. Returns the pipeline."
  [port handler]
  (let [channel-factory (NioServerSocketChannelFactory.
                          (Executors/newCachedThreadPool)
                          (Executors/newCachedThreadPool))
        bootstrap (ServerBootstrap. channel-factory)
        pipeline (.getPipeline bootstrap)]
    (.addLast pipeline "handler" (make-handler))
    (.setOption bootstrap "child.tcpNoDelay", true)
    (.setOption bootstrap "child.keepAlive", true)
    (.bind bootstrap (InetSocketAddress. port))
    pipeline))

(defn make-handler
  "Returns a Netty handler."
  []
  (proxy [SimpleChannelHandler] []
    (channelConnected [ctx e]
      (let [c (.getChannel e)]
        (println "Connected:" c)))

    (channelDisconnected [ctx e]
      (let [c (.getChannel e)]
        (println "Disconnected:" c)))

    (messageReceived [ctx e]
      (let [c (.getChannel e)
            cb (.getMessage e)
            msg (.toString cb "UTF-8")]
        (println "Message:" msg "from" c)))

    (exceptionCaught
      [ctx e]
      (let [throwable (.getCause e)]
        (println "@exceptionCaught" throwable))
      (-> e .getChannel .close))))