Netty之旅二：口口相傳的高性能Netty到底是什麼？

{"type":"doc","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/ad/adc61b03ce4460399a0adb2b07e8a74b.png","alt":"d0iosx.png","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"高清思維導圖原件("},{"type":"codeinline","content":[{"type":"text","text":"xmind/pdf/jpg"}]},{"type":"text","text":")可以關注公衆號："},{"type":"codeinline","content":[{"type":"text","text":"一枝花算不算浪漫"}]},{"type":"text","text":" 回覆"},{"type":"codeinline","content":[{"type":"text","text":"netty01"}]},{"type":"text","text":"即可。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"前言"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上一篇文章講了"},{"type":"codeinline","content":[{"type":"text","text":"NIO"}]},{"type":"text","text":"相關的知識點，相比於傳統"},{"type":"codeinline","content":[{"type":"text","text":"IO"}]},{"type":"text","text":"，"},{"type":"codeinline","content":[{"type":"text","text":"NIO"}]},{"type":"text","text":"已經做得很優雅了，爲什麼我們還要使用"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"？"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"上篇文章最後留了很多坑，講了"},{"type":"codeinline","content":[{"type":"text","text":"NIO"}]},{"type":"text","text":"使用的弊端，也是爲了引出"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"而設立的，這篇文章我們就來好好揭開"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"的神祕面紗。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"本篇文章的目的很簡單，希望看過後你能看懂"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"的示例代碼，針對於簡單的網絡通信，自己也能用"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"手寫一個開發應用出來！"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"一個簡單的Netty示例"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"以下是一個簡單聊天室Server端的程序，代碼參考自："},{"type":"codeinline","content":[{"type":"text","text":"http://www.imooc.com/read/82/article/2166"}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"代碼有點長，主要核心代碼是在"},{"type":"codeinline","content":[{"type":"text","text":"main()"}]},{"type":"text","text":"方法中，這裏代碼也希望大家看懂，後面也會一步步剖析。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"PS：我是用"},{"type":"codeinline","content":[{"type":"text","text":"mac"}]},{"type":"text","text":"系統，直接在終端輸入"},{"type":"codeinline","content":[{"type":"text","text":"telnet 127.0.0.1 8007"}]},{"type":"text","text":" 即可啓動一個聊天框，如果提示找不到"},{"type":"codeinline","content":[{"type":"text","text":"telnet"}]},{"type":"text","text":"命令，可以通過"},{"type":"codeinline","content":[{"type":"text","text":"brew"}]},{"type":"text","text":"進行安裝，具體步驟請自行百度。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"/**\n * @Description netty簡易聊天室\n *\n * @Author 一枝花算不算浪漫\n * @Date 2020/8/10 6:52 上午\n */\npublic final class NettyChatServer {\n\n static final int PORT = Integer.parseInt(System.getProperty(\"port\", \"8007\"));\n\n public static void main(String[] args) throws Exception {\n // 1. EventLoopGroup\n EventLoopGroup bossGroup = new NioEventLoopGroup(1);\n EventLoopGroup workerGroup = new NioEventLoopGroup();\n try {\n // 2. 服務端引導器\n ServerBootstrap serverBootstrap = new ServerBootstrap();\n // 3. 設置線bootStrap信息\n serverBootstrap.group(bossGroup, workerGroup)\n // 4. 設置ServerSocketChannel的類型\n .channel(NioServerSocketChannel.class)\n // 5. 設置參數\n .option(ChannelOption.SO_BACKLOG, 100)\n // 6. 設置ServerSocketChannel對應的Handler，只能設置一個\n .handler(new LoggingHandler(LogLevel.INFO))\n // 7. 設置SocketChannel對應的Handler\n .childHandler(new ChannelInitializer() {\n @Override\n public void initChannel(SocketChannel ch) throws Exception {\n ChannelPipeline p = ch.pipeline();\n // 可以添加多個子Handler\n p.addLast(new LoggingHandler(LogLevel.INFO));\n p.addLast(new ChatNettyHandler());\n }\n });\n\n // 8. 綁定端口\n ChannelFuture f = serverBootstrap.bind(PORT).sync();\n // 9. 等待服務端監聽端口關閉，這裏會阻塞主線程\n f.channel().closeFuture().sync();\n } finally {\n // 10. 優雅地關閉兩個線程池\n bossGroup.shutdownGracefully();\n workerGroup.shutdownGracefully();\n }\n }\n\n private static class ChatNettyHandler extends SimpleChannelInboundHandler {\n @Override\n public void channelActive(ChannelHandlerContext ctx) {\n System.out.println(\"one conn active: \" + ctx.channel());\n // channel是在ServerBootstrapAcceptor中放到EventLoopGroup中的\n ChatHolder.join((SocketChannel) ctx.channel());\n }\n\n @Override\n protected void channelRead0(ChannelHandlerContext ctx, ByteBuf byteBuf) throws Exception {\n byte[] bytes = new byte[byteBuf.readableBytes()];\n byteBuf.readBytes(bytes);\n String content = new String(bytes, StandardCharsets.UTF_8);\n System.out.println(content);\n\n if (content.equals(\"quit\\r\\n\")) {\n ctx.channel().close();\n } else {\n ChatHolder.propagate((SocketChannel) ctx.channel(), content);\n }\n }\n\n @Override\n public void channelInactive(ChannelHandlerContext ctx) {\n System.out.println(\"one conn inactive: \" + ctx.channel());\n ChatHolder.quit((SocketChannel) ctx.channel());\n }\n }\n\n private static class ChatHolder {\n static final Map USER_MAP = new ConcurrentHashMap<>();\n\n /**\n * 加入羣聊\n */\n static void join(SocketChannel socketChannel) {\n // 有人加入就給他分配一個id\n String userId = \"用戶\"+ ThreadLocalRandom.current().nextInt(Integer.MAX_VALUE);\n send(socketChannel, \"您的id爲：\" + userId + \"\\n\\r\");\n\n for (SocketChannel channel : USER_MAP.keySet()) {\n send(channel, userId + \" 加入了羣聊\" + \"\\n\\r\");\n }\n\n // 將當前用戶加入到map中\n USER_MAP.put(socketChannel, userId);\n }\n\n /**\n * 退出羣聊\n */\n static void quit(SocketChannel socketChannel) {\n String userId = USER_MAP.get(socketChannel);\n send(socketChannel, \"您退出了羣聊\" + \"\\n\\r\");\n USER_MAP.remove(socketChannel);\n\n for (SocketChannel channel : USER_MAP.keySet()) {\n if (channel != socketChannel) {\n send(channel, userId + \" 退出了羣聊\" + \"\\n\\r\");\n }\n }\n }\n\n /**\n * 擴散說話的內容\n */\n public static void propagate(SocketChannel socketChannel, String content) {\n String userId = USER_MAP.get(socketChannel);\n for (SocketChannel channel : USER_MAP.keySet()) {\n if (channel != socketChannel) {\n send(channel, userId + \": \" + content);\n }\n }\n }\n\n /**\n * 發送消息\n */\n static void send(SocketChannel socketChannel, String msg) {\n try {\n ByteBufAllocator allocator = ByteBufAllocator.DEFAULT;\n ByteBuf writeBuffer = allocator.buffer(msg.getBytes().length);\n writeBuffer.writeCharSequence(msg, Charset.defaultCharset());\n socketChannel.writeAndFlush(writeBuffer);\n } catch (Exception e) {\n e.printStackTrace();\n }\n }\n }\n}"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/a6/a6b3e3d6d3df87bea45eccf2f02e3b7b.png","alt":"dkeb0s.png","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"代碼有點長，執行完的效果如上圖所示，下面所有內容都是圍繞着"},{"type":"codeinline","content":[{"type":"text","text":"如何看懂"}]},{"type":"text","text":"以及"},{"type":"codeinline","content":[{"type":"text","text":"如何寫出"}]},{"type":"text","text":"這樣的代碼來展開的，希望你看完 也能輕鬆手寫"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"服務端代碼~。通過簡單demo開發讓大家體驗了"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"實現相比"},{"type":"codeinline","content":[{"type":"text","text":"NIO"}]},{"type":"text","text":"確實要簡單的多，但優點不限於此，只需要知道選擇Netty就對了。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":2},"content":[{"type":"text","text":"Netty核心組件"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"對應着文章開頭的思維導圖，我們知道"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"的核心組件主要有："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Bootstrap 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ServerBootstrap"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"EventLoopGroup"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"EventLoop"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ByteBuf"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"Channel"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ChannelHandler"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ChannelFuture"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ChannelPipeline"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"ChannelHandlerContext"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"類圖如下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/d2/d26a6eeaf925fe55e05d449a1f427f48.png","alt":"dk8ZC9.png","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"Bootstrap & ServerBootstrap"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"一看到"},{"type":"codeinline","content":[{"type":"text","text":"BootStrap"}]},{"type":"text","text":"大家就應該想到"},{"type":"text","marks":[{"type":"strong"}],"text":"啓動類、引導類"},{"type":"text","text":"這樣的詞彙，之前分析過[EurekaServer項目啓動類時][1]介紹過"},{"type":"codeinline","content":[{"type":"text","text":"EurekaBootstrap"}]},{"type":"text","text":"， 他的作用就是上下文初始化、配置初始化。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"在"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"中我們也有類似的類，"},{"type":"codeinline","content":[{"type":"text","text":"Bootstrap"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"它們都是"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"程序的引導類，主要用於配置各種參數，並啓動整個"},{"type":"codeinline","content":[{"type":"text","text":"Netty"}]},{"type":"text","text":"服務，我們看下文章開頭的示例代碼："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"codeblock","attrs":{"lang":"java"},"content":[{"type":"text","text":"ServerBootstrap serverBootstrap = new ServerBootstrap();\nserverBootstrap.group(bossGroup, workerGroup) \n .channel(NioServerSocketChannel.class)\n .option(ChannelOption.SO_BACKLOG, 100)\n .handler(new LoggingHandler(LogLevel.INFO))\n .childHandler(new ChannelInitializer() {\n @Override\n public void initChannel(SocketChannel ch) throws Exception {\n ChannelPipeline p = ch.pipeline();\n p.addLast(new LoggingHandler(LogLevel.INFO));\n p.addLast(new ChatNettyHandler());\n }\n });"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Bootstrap"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"是針對於"},{"type":"codeinline","content":[{"type":"text","text":"Client"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"Server"}]},{"type":"text","text":"端定義的兩套啓動類，區別如下："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Bootstrap"}]},{"type":"text","text":"是客戶端引導類，而"},{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"是服務端引導類。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Bootstrap"}]},{"type":"text","text":"通常使用"},{"type":"codeinline","content":[{"type":"text","text":"connect()"}]},{"type":"text","text":"方法連接到遠程的主機和端口，作爲一個"},{"type":"codeinline","content":[{"type":"text","text":"TCP客戶端"}]},{"type":"text","text":"。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"通常使用"},{"type":"codeinline","content":[{"type":"text","text":"bind()"}]},{"type":"text","text":"方法綁定本地的端口，等待客戶端來連接。"}]}]},{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"可以處理"},{"type":"codeinline","content":[{"type":"text","text":"Accept"}]},{"type":"text","text":"事件，這裏面"},{"type":"codeinline","content":[{"type":"text","text":"childHandler"}]},{"type":"text","text":"是用來處理"},{"type":"codeinline","content":[{"type":"text","text":"Channel"}]},{"type":"text","text":"請求的，我們可以查看"},{"type":"codeinline","content":[{"type":"text","text":"chaildHandler()"}]},{"type":"text","text":"方法的註解："}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/26/26ef7f0cbf0694c41594c355df2cdbe7.png","alt":"dk884H.png","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"bulletedlist","content":[{"type":"listitem","content":[{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"Bootstrap"}]},{"type":"text","text":"客戶端引導只需要一個"},{"type":"codeinline","content":[{"type":"text","text":"EventLoopGroup"}]},{"type":"text","text":"，但是一個"},{"type":"codeinline","content":[{"type":"text","text":"ServerBootstrap"}]},{"type":"text","text":"通常需要兩個(上面的"},{"type":"codeinline","content":[{"type":"text","text":"boosGroup"}]},{"type":"text","text":"和"},{"type":"codeinline","content":[{"type":"text","text":"workerGroup"}]},{"type":"text","text":")。"}]}]}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"heading","attrs":{"align":null,"level":3},"content":[{"type":"text","text":"EventLoopGroup && EventLoop"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"EventLoopGroup"}]},{"type":"text","text":"及"},{"type":"codeinline","content":[{"type":"text","text":"EventLoop"}]},{"type":"text","text":"這兩個類名稱定義的很奇怪，對於初學者來說往往無法通過名稱來了解其中的含義，包括我也是這樣。"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"EventLoopGroup"}]},{"type":"text","text":" 可以理解爲一個線程池，對於服務端程序，我們一般會綁定兩個線程池，一個用於處理 "},{"type":"codeinline","content":[{"type":"text","text":"Accept"}]},{"type":"text","text":" 事件，一個用於處理讀寫事件，看下"},{"type":"codeinline","content":[{"type":"text","text":"EventLoop"}]},{"type":"text","text":"系列的類目錄："}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"image","attrs":{"src":"https://static001.geekbang.org/infoq/95/95db84fe7d25dee1eb926fa98f163b96.png","alt":"dU4Roj.png","title":null,"style":null,"href":null,"fromPaste":true,"pastePass":true}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"text","text":"通過上面的類圖，我們才恍然大悟，我的親孃咧，這不就是一個線程池嘛？(名字氣的犄角拐彎的真是難認)"}]},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null}},{"type":"paragraph","attrs":{"indent":0,"number":0,"align":null,"origin":null},"content":[{"type":"codeinline","content":[{"type":"text","text":"EventLoopGroup"}]},{"type":"text","text":"是"},{"type":"codeinline","content":[{"type":"text","text":"EventLoop"}]},{"type":"text","text":"的集合，一個"},{"type":"codeinline","content":[{"type":"text","text":"EventLoopGroup"}]},{"type":"text","text":" 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