使用Clojure進行服務器編程

Question

如何在Clojure中實現10k連接回顯服務器？

clojure.contrib.server-socket不是答案，因爲它爲每個連接創建一個新的操作系統線程。

Answer 1

關於Clojure的好處是你擁有所有這些優秀的庫，像JVM，如netty，這些JVM經過高度優化，可配置和深思熟慮。像這樣的東西應該讓你去：

(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))))