代理网关设计与实现(基于NETTY)

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2021年11月24日12:51:00
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摘要

智能摘要

智能摘要

本文要构建代理网关,本质上就是一个非透明的上游代理,并给出详细的设计与实现。代理服务在收到代理请求时,首先做代理的预处理,然后又SocketPipe做客户端和远程服务端双向转发。最后,拿到请求后,做相应的处理,最终实现非透明的代理。只需要对透明代理做以上简单的修改,即可实现透明的上游代理。实时处理的请求数量*请求体的平均大小,HTTP/HTTPS的请求结果,直接使用堆外内存,零拷贝转发。

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代理网关设计与实现(基于NETTY)

原创 新然 阿里技术

收录于话题#Java81个内容

代理网关设计与实现(基于NETTY)

一  问题背景

平台端购置一批裸代理,来做广告异地展现审核。从外部购置的代理,使用方式为:

  1. 通过给定的HTTP 的 API 提取代理 IP:PORT,返回的结果会给出代理的有效时长 3~5 分钟,以及代理所属地域;

  2. 从提取的代理中,选取指定地域,添加认证信息,请求获取结果;

本文设计实现一个通过的代理网关:

  1. 管理维护代理资源,并做代理的认证鉴权;

  2. 对外暴露统一的代理入口,而非动态变化的代理IP:PORT;

  3. 流量过滤及限流,比如:静态资源不走代理;

本文重点在代理网关本身的设计与实现,而非代理资源的管理与维护。

注:本文包含大量可执行的JAVA代码以解释代理相关的原理

二  技术路线

本文的技术路线。在实现代理网关之前,首先介绍下代理相关的原理及如何实现

  1. 透明代理;

  2. 非透明代理;

  3. 透明的上游代理;

  4. 非透明的上游代理;

最后,本文要构建代理网关,本质上就是一个非透明的上游代理,并给出详细的设计与实现。

1  透明代理

透明代理是代理网关的基础,本文采用JAVA原生的NIO进行详细介绍。在实现代理网关时,实际使用的为NETTY框架。原生NIO的实现对理解NETTY的实现有帮助。

透明代理设计三个交互方,客户端、代理服务、服务端,其原理是:

代理网关设计与实现(基于NETTY)

  1. 代理服务在收到连接请求时,判定:如果是CONNECT请求,需要回应代理连接成功消息到客户端;

  2. CONNECT请求回应结束后,代理服务需要连接到CONNECT指定的远程服务器,然后直接转发客户端和远程服务通信;

  3. 代理服务在收到非CONNECT请求时,需要解析出请求的远程服务器,然后直接转发客户端和远程服务通信;

需要注意的点是:

  1. 通常HTTPS请求,在通过代理前,会发送CONNECT请求;连接成功后,会在信道上进行加密通信的握手协议;因此连接远程的时机是在CONNECT请求收到时,因为此后是加密数据;

  2. 透明代理在收到CONNECT请求时,不需要传递到远程服务(远程服务不识别此请求);

  3. 透明代理在收到非CONNECT请求时,要无条件转发;

完整的透明代理的实现不到约300行代码,完整摘录如下:

@Slf4jpublicclassSimpleTransProxy{publicstaticvoidmain(String[] args)throws IOException {int port = 8006; ServerSocketChannel localServer = ServerSocketChannel.open(); localServer.bind(new InetSocketAddress(port)); Reactor reactor = new Reactor();// REACTOR线程 GlobalThreadPool.REACTOR_EXECUTOR.submit(reactor::run);// WORKER单线程调试while (localServer.isOpen()) {// 此处阻塞等待连接 SocketChannel remoteClient = localServer.accept();// 工作线程 GlobalThreadPool.WORK_EXECUTOR.submit(new Runnable() {@SneakyThrows@Overridepublicvoidrun(){// 代理到远程 SocketChannel remoteServer = new ProxyHandler().proxy(remoteClient);// 透明传输 reactor.pipe(remoteClient, remoteServer) .pipe(remoteServer, remoteClient); } }); } }}@DataclassProxyHandler{private String method;private String host;privateint port;private SocketChannel remoteServer;private SocketChannel remoteClient;/** * 原始信息 */private List<ByteBuffer> buffers = new ArrayList<>();private StringBuilder stringBuilder = new StringBuilder();/** * 连接到远程 * @param remoteClient * @return * @throws IOException */public SocketChannel proxy(SocketChannel remoteClient)throws IOException {this.remoteClient = remoteClient; connect();returnthis.remoteServer; }publicvoidconnect()throws IOException {// 解析METHOD, HOST和PORT beforeConnected();// 链接REMOTE SERVER createRemoteServer();// CONNECT请求回应,其他请求WRITE THROUGH afterConnected(); }protectedvoidbeforeConnected()throws IOException {// 读取HEADER readAllHeader();// 解析HOST和PORT parseRemoteHostAndPort(); }/** * 创建远程连接 * @throws IOException */protectedvoidcreateRemoteServer()throws IOException { remoteServer = SocketChannel.open(new InetSocketAddress(host, port)); }/** * 连接建立后预处理 * @throws IOException */protectedvoidafterConnected()throws IOException {// 当CONNECT请求时,默认写入200到CLIENTif ("CONNECT".equalsIgnoreCase(method)) {// CONNECT默认为443端口,根据HOST再解析 remoteClient.write(ByteBuffer.wrap("HTTP/1.0 200 Connection Established\r\nProxy-agent: nginx\r\n\r\n".getBytes())); } else { writeThrouth(); } }protectedvoidwriteThrouth(){ buffers.forEach(byteBuffer -> {try { remoteServer.write(byteBuffer); } catch (IOException e) { e.printStackTrace(); } }); }/** * 读取请求内容 * @throws IOException */protectedvoidreadAllHeader()throws IOException {while (true) { ByteBuffer clientBuffer = newByteBuffer();int read = remoteClient.read(clientBuffer); clientBuffer.flip(); appendClientBuffer(clientBuffer);if (read < clientBuffer.capacity()) {break; } } }/** * 解析出HOST和PROT * @throws IOException */protectedvoidparseRemoteHostAndPort()throws IOException {// 读取第一批,获取到METHOD method = parseRequestMethod(stringBuilder.toString());// 默认为80端口,根据HOST再解析 port = 80;if ("CONNECT".equalsIgnoreCase(method)) { port = 443; }this.host = parseHost(stringBuilder.toString()); URI remoteServerURI = URI.create(host); host = remoteServerURI.getHost();if (remoteServerURI.getPort() > 0) { port = remoteServerURI.getPort(); } }protectedvoidappendClientBuffer(ByteBuffer clientBuffer){ buffers.add(clientBuffer); stringBuilder.append(new String(clientBuffer.array(), clientBuffer.position(), clientBuffer.limit())); }protectedstatic ByteBuffer newByteBuffer(){// buffer必须大于7,保证能读到methodreturn ByteBuffer.allocate(128); }privatestatic String parseRequestMethod(String rawContent){// create urireturn rawContent.split("\r\n")[0].split(" ")[0]; }privatestatic String parseHost(String rawContent){ String[] headers = rawContent.split("\r\n"); String host = "host:";for (String header : headers) {if (header.length() > host.length()) { String key = header.substring(0, host.length()); String value = header.substring(host.length()).trim();if (host.equalsIgnoreCase(key)) {if (!value.startsWith("http://") && !value.startsWith("https://")) { value = "http://" + value; }return value; } } }return""; }}@Slf4j@DataclassReactor{private Selector selector;privatevolatileboolean finish = false;@SneakyThrowspublicReactor(){ selector = Selector.open(); }@SneakyThrowspublic Reactor pipe(SocketChannel from, SocketChannel to){ from.configureBlocking(false); from.register(selector, SelectionKey.OP_READ, new SocketPipe(this, from, to));returnthis; }@SneakyThrowspublicvoidrun(){try {while (!finish) {if (selector.selectNow() > 0) { Iterator<SelectionKey> it = selector.selectedKeys().iterator();while (it.hasNext()) { SelectionKey selectionKey = it.next();if (selectionKey.isValid() && selectionKey.isReadable()) { ((SocketPipe) selectionKey.attachment()).pipe(); } it.remove(); } } } } finally { close(); } }@SneakyThrowspublicsynchronizedvoidclose(){if (finish) {return; } finish = true;if (!selector.isOpen()) {return; }for (SelectionKey key : selector.keys()) { closeChannel(key.channel()); key.cancel(); }if (selector != null) { selector.close(); } }publicvoidcancel(SelectableChannel channel){ SelectionKey key = channel.keyFor(selector);if (Objects.isNull(key)) {return; } key.cancel(); }@SneakyThrowspublicvoidcloseChannel(Channel channel){ SocketChannel socketChannel = (SocketChannel)channel;if (socketChannel.isConnected() && socketChannel.isOpen()) { socketChannel.shutdownOutput(); socketChannel.shutdownInput(); } socketChannel.close(); }}@Data@AllArgsConstructorclassSocketPipe{private Reactor reactor;private SocketChannel from;private SocketChannel to;@SneakyThrowspublicvoidpipe(){// 取消监听 clearInterestOps(); GlobalThreadPool.PIPE_EXECUTOR.submit(new Runnable() {@SneakyThrows@Overridepublicvoidrun(){int totalBytesRead = 0; ByteBuffer byteBuffer = ByteBuffer.allocate(1024);while (valid(from) && valid(to)) { byteBuffer.clear();int bytesRead = from.read(byteBuffer); totalBytesRead = totalBytesRead + bytesRead; byteBuffer.flip(); to.write(byteBuffer);if (bytesRead < byteBuffer.capacity()) {break; } }if (totalBytesRead < 0) { reactor.closeChannel(from); reactor.cancel(from); } else {// 重置监听 resetInterestOps(); } } }); }protectedvoidclearInterestOps(){ from.keyFor(reactor.getSelector()).interestOps(0); to.keyFor(reactor.getSelector()).interestOps(0); }protectedvoidresetInterestOps(){ from.keyFor(reactor.getSelector()).interestOps(SelectionKey.OP_READ); to.keyFor(reactor.getSelector()).interestOps(SelectionKey.OP_READ); }privatebooleanvalid(SocketChannel channel){return channel.isConnected() && channel.isRegistered() && channel.isOpen(); }}

以上,借鉴NETTY

  1. 首先初始化REACTOR线程,然后开启代理监听,当收到代理请求时处理。

  2. 代理服务在收到代理请求时,首先做代理的预处理,然后又SocketPipe做客户端和远程服务端双向转发。

  3. 代理预处理,首先读取第一个HTTP请求,解析出METHOD, HOST, PORT

  4. 如果是CONNECT请求,发送回应Connection Established,然后连接远程服务端,并返回SocketChannel

  5. 如果是非CONNECT请求,连接远程服务端,写入原始请求,并返回SocketChannel

  6. SocketPipe在客户端和远程服务端,做双向的转发;其本身是将客户端和服务端的SocketChannel注册到REACTOR

  7. REACTOR在监测到READABLECHANNEL,派发给SocketPipe做双向转发。

测试

代理的测试比较简单,指向代码后,代理服务监听8006端口,此时:

curl -x 'localhost:8006' http://httpbin.org/get测试HTTP请求

curl -x 'localhost:8006' https://httpbin.org/get测试HTTPS请求

注意,此时代理服务代理了HTTPS请求,但是并不需要-k选项,指示非安全的代理。因为代理服务本身并没有作为一个中间人,并没有解析出客户端和远程服务端通信的内容。在非透明代理时,需要解决这个问题。

2  非透明代理

非透明代理,需要解析出客户端和远程服务端传输的内容,并做相应的处理。

当传输为HTTP协议时,SocketPipe传输的数据即为明文的数据,可以拦截后直接做处理。

当传输为HTTPS协议时,SocketPipe传输的有效数据为加密数据,并不能透明处理。另外,无论是传输的HTTP协议还是HTTPS协议,SocketPipe读到的都为非完整的数据,需要做聚批的处理。

  1. SocketPipe聚批问题,可以采用类似BufferedInputStreamInputStreamDecorate的模式来实现,相对比较简单;详细可以参考NETTYHttpObjectAggregator

  2. HTTPS原始请求和结果数据的加密和解密的处理,需要实现的NIOSOCKET CHANNEL;

SslSocketChannel封装原理

考虑到目前JDK自带的NIOSocketChannel并不支持SSL;已有的SSLSocket是阻塞的OIO如图:

代理网关设计与实现(基于NETTY)

可以看出

  1. 每次入站数据和出站数据都需要 SSL SESSION 做握手;

  2. 入站数据做解密,出站数据做加密;

  3. 握手,数据加密和数据解密是统一的一套状态机;

代理网关设计与实现(基于NETTY)

以下,代码实现 SslSocketChannel

publicclassSslSocketChannel{/** * 握手加解密需要的四个存储 */protected ByteBuffer myAppData; // 明文protected ByteBuffer myNetData; // 密文protected ByteBuffer peerAppData; // 明文protected ByteBuffer peerNetData; // 密文/** * 握手加解密过程中用到的异步执行器 */protected ExecutorService executor = Executors.newSingleThreadExecutor();/** * 原NIO 的 CHANNEL */protected SocketChannel socketChannel;/** * SSL 引擎 */protected SSLEngine engine;publicSslSocketChannel(SSLContext context, SocketChannel socketChannel, boolean clientMode)throws Exception {// 原始的NIO SOCKETthis.socketChannel = socketChannel;// 初始化BUFFER SSLSession dummySession = context.createSSLEngine().getSession(); myAppData = ByteBuffer.allocate(dummySession.getApplicationBufferSize()); myNetData = ByteBuffer.allocate(dummySession.getPacketBufferSize()); peerAppData = ByteBuffer.allocate(dummySession.getApplicationBufferSize()); peerNetData = ByteBuffer.allocate(dummySession.getPacketBufferSize()); dummySession.invalidate(); engine = context.createSSLEngine(); engine.setUseClientMode(clientMode); engine.beginHandshake(); }/** * 参考 https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html * 实现的 SSL 的握手协议 * @return * @throws IOException */protectedbooleandoHandshake()throws IOException { SSLEngineResult result; HandshakeStatus handshakeStatus;int appBufferSize = engine.getSession().getApplicationBufferSize(); ByteBuffer myAppData = ByteBuffer.allocate(appBufferSize); ByteBuffer peerAppData = ByteBuffer.allocate(appBufferSize); myNetData.clear(); peerNetData.clear(); handshakeStatus = engine.getHandshakeStatus();while (handshakeStatus != HandshakeStatus.FINISHED && handshakeStatus != HandshakeStatus.NOT_HANDSHAKING) {switch (handshakeStatus) {case NEED_UNWRAP:if (socketChannel.read(peerNetData) < 0) {if (engine.isInboundDone() && engine.isOutboundDone()) {returnfalse; }try { engine.closeInbound(); } catch (SSLException e) { log.debug("收到END OF STREAM,关闭连接.", e); } engine.closeOutbound(); handshakeStatus = engine.getHandshakeStatus();break; } peerNetData.flip();try { result = engine.unwrap(peerNetData, peerAppData); peerNetData.compact(); handshakeStatus = result.getHandshakeStatus(); } catch (SSLException sslException) { engine.closeOutbound(); handshakeStatus = engine.getHandshakeStatus();break; }switch (result.getStatus()) {case OK:break;case BUFFER_OVERFLOW: peerAppData = enlargeApplicationBuffer(engine, peerAppData);break;case BUFFER_UNDERFLOW: peerNetData = handleBufferUnderflow(engine, peerNetData);break;case CLOSED:if (engine.isOutboundDone()) {returnfalse; } else { engine.closeOutbound(); handshakeStatus = engine.getHandshakeStatus();break; }default:thrownew IllegalStateException("无效的握手状态: " + result.getStatus()); }break;case NEED_WRAP: myNetData.clear();try { result = engine.wrap(myAppData, myNetData); handshakeStatus = result.getHandshakeStatus(); } catch (SSLException sslException) { engine.closeOutbound(); handshakeStatus = engine.getHandshakeStatus();break; }switch (result.getStatus()) {case OK : myNetData.flip();while (myNetData.hasRemaining()) { socketChannel.write(myNetData); }break;case BUFFER_OVERFLOW: myNetData = enlargePacketBuffer(engine, myNetData);break;case BUFFER_UNDERFLOW:thrownew SSLException("加密后消息内容为空,报错");case CLOSED:try { myNetData.flip();while (myNetData.hasRemaining()) { socketChannel.write(myNetData); } peerNetData.clear(); } catch (Exception e) { handshakeStatus = engine.getHandshakeStatus(); }break;default:thrownew IllegalStateException("无效的握手状态: " + result.getStatus()); }break;case NEED_TASK: Runnable task;while ((task = engine.getDelegatedTask()) != null) { executor.execute(task); } handshakeStatus = engine.getHandshakeStatus();break;case FINISHED:break;case NOT_HANDSHAKING:break;default:thrownew IllegalStateException("无效的握手状态: " + handshakeStatus); } }returntrue; }/** * 参考 https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html * 实现的 SSL 的传输读取协议 * @param consumer * @throws IOException */publicvoidread(Consumer<ByteBuffer> consumer)throws IOException {// BUFFER初始化 peerNetData.clear();int bytesRead = socketChannel.read(peerNetData);if (bytesRead > 0) { peerNetData.flip();while (peerNetData.hasRemaining()) { peerAppData.clear(); SSLEngineResult result = engine.unwrap(peerNetData, peerAppData);switch (result.getStatus()) {case OK: log.debug("收到远程的返回结果消息为:" + new String(peerAppData.array(), 0, peerAppData.position())); consumer.accept(peerAppData); peerAppData.flip();break;case BUFFER_OVERFLOW: peerAppData = enlargeApplicationBuffer(engine, peerAppData);break;case BUFFER_UNDERFLOW: peerNetData = handleBufferUnderflow(engine, peerNetData);break;case CLOSED: log.debug("收到远程连接关闭消息."); closeConnection();return;default:thrownew IllegalStateException("无效的握手状态: " + result.getStatus()); } } } elseif (bytesRead < 0) { log.debug("收到END OF STREAM,关闭连接."); handleEndOfStream(); } }publicvoidwrite(String message)throws IOException { write(ByteBuffer.wrap(message.getBytes())); }/** * 参考 https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html * 实现的 SSL 的传输写入协议 * @param message * @throws IOException */publicvoidwrite(ByteBuffer message)throws IOException { myAppData.clear(); myAppData.put(message); myAppData.flip();while (myAppData.hasRemaining()) { myNetData.clear(); SSLEngineResult result = engine.wrap(myAppData, myNetData);switch (result.getStatus()) {case OK: myNetData.flip();while (myNetData.hasRemaining()) { socketChannel.write(myNetData); } log.debug("写入远程的消息为: {}", message);break;case BUFFER_OVERFLOW: myNetData = enlargePacketBuffer(engine, myNetData);break;case BUFFER_UNDERFLOW:thrownew SSLException("加密后消息内容为空.");case CLOSED: closeConnection();return;default:thrownew IllegalStateException("无效的握手状态: " + result.getStatus()); } } }/** * 关闭连接 * @throws IOException */publicvoidcloseConnection()throws IOException { engine.closeOutbound(); doHandshake(); socketChannel.close(); executor.shutdown(); }/** * END OF STREAM(-1)默认是关闭连接 * @throws IOException */protectedvoidhandleEndOfStream()throws IOException {try { engine.closeInbound(); } catch (Exception e) { log.error("END OF STREAM 关闭失败.", e); } closeConnection(); }}

以上:

  1. 基于 SSL 协议,实现统一的握手动作;

  2. 分别实现读取的解密,和写入的加密方法;

  3. 将 SslSocketChannel 实现为 SocketChannelDecorator;

SslSocketChannel测试服务端

基于以上封装,简单测试服务端如下

@Slf4jpublicclassNioSslServer {publicstaticvoidmain(String[] args) throws Exception { NioSslServer sslServer = new NioSslServer("127.0.0.1", 8006); sslServer.start();// 使用 curl -vv -k 'https://localhost:8006' 连接 }private SSLContext context;private Selector selector;publicNioSslServer(String hostAddress, int port) throws Exception {// 初始化SSL Context context = serverSSLContext();// 注册监听器 selector = SelectorProvider.provider().openSelector(); ServerSocketChannel serverSocketChannel = ServerSocketChannel.open(); serverSocketChannel.configureBlocking(false); serverSocketChannel.socket().bind(new InetSocketAddress(hostAddress, port)); serverSocketChannel.register(selector, SelectionKey.OP_ACCEPT); }publicvoidstart() throws Exception {log.debug("等待连接中.");while (true) { selector.select(); Iterator<SelectionKey> selectedKeys = selector.selectedKeys().iterator();while (selectedKeys.hasNext()) { SelectionKey key = selectedKeys.next(); selectedKeys.remove();if (!key.isValid()) {continue; }if (key.isAcceptable()) { accept(key); } elseif (key.isReadable()) { ((SslSocketChannel)key.attachment()).read(buf->{});// 直接回应一个OK ((SslSocketChannel)key.attachment()).write("HTTP/1.1 200 OK\r\nContent-Type: text/plain\r\n\r\nOK\r\n\r\n"); ((SslSocketChannel)key.attachment()).closeConnection(); } } } }privatevoidaccept(SelectionKey key) throws Exception {log.debug("接收新的请求."); SocketChannel socketChannel = ((ServerSocketChannel)key.channel()).accept(); socketChannel.configureBlocking(false); SslSocketChannel sslSocketChannel = new SslSocketChannel(context, socketChannel, false);if (sslSocketChannel.doHandshake()) { socketChannel.register(selector, SelectionKey.OP_READ, sslSocketChannel); } else { socketChannel.close();log.debug("握手失败,关闭连接."); } }}

以上:

  1. 由于是NIO,简单的测试需要用到NIO的基础组件Selector进行测试;

  2. 首先初始化ServerSocketChannel,监听8006端口;

  3. 接收到请求后,将SocketChannel封装为SslSocketChannel,注册到Selector

  4. 接收到数据后,通过SslSocketChannelreadwrite

SslSocketChannel测试客户端

基于以上服务端封装,简单测试客户端如下

@Slf4jpublicclassNioSslClient{publicstaticvoidmain(String[] args)throws Exception { NioSslClient sslClient = new NioSslClient("httpbin.org", 443); sslClient.connect();// 请求 'https://httpbin.org/get' }private String remoteAddress;privateint port;private SSLEngine engine;private SocketChannel socketChannel;private SSLContext context;/** * 需要远程的HOST和PORT * @param remoteAddress * @param port * @throws Exception */publicNioSslClient(String remoteAddress, int port)throws Exception {this.remoteAddress = remoteAddress;this.port = port; context = clientSSLContext(); engine = context.createSSLEngine(remoteAddress, port); engine.setUseClientMode(true); }publicbooleanconnect()throws Exception { socketChannel = SocketChannel.open(); socketChannel.configureBlocking(false); socketChannel.connect(new InetSocketAddress(remoteAddress, port));while (!socketChannel.finishConnect()) {// 通过REACTOR,不会出现等待情况//log.debug("连接中.."); } SslSocketChannel sslSocketChannel = new SslSocketChannel(context, socketChannel, true); sslSocketChannel.doHandshake();// 握手完成后,开启SELECTOR Selector selector = SelectorProvider.provider().openSelector(); socketChannel.register(selector, SelectionKey.OP_READ, sslSocketChannel);// 写入请求 sslSocketChannel.write("GET /get HTTP/1.1\r\n" + "Host: httpbin.org:443\r\n" + "User-Agent: curl/7.62.0\r\n" + "Accept: */*\r\n" + "\r\n");// 读取结果while (true) { selector.select(); Iterator<SelectionKey> selectedKeys = selector.selectedKeys().iterator();while (selectedKeys.hasNext()) { SelectionKey key = selectedKeys.next(); selectedKeys.remove();if (key.isValid() && key.isReadable()) { ((SslSocketChannel)key.attachment()).read(buf->{ log.info("{}", new String(buf.array(), 0, buf.position())); }); ((SslSocketChannel)key.attachment()).closeConnection();returntrue; } } } }}

以上:

  1. 客户端的封装测试,是为了验证封装 SSL 协议双向都是OK的,

  2. 在后文的非透明上游代理中,会同时使用 SslSocketChannel做服务端和客户端

  3. 以上封装与服务端封装类似,不同的是初始化 SocketChannel,做connect而非bind

总结

以上:

  1. 非透明代理需要拿到完整的请求数据,可以通过 Decorator模式,聚批实现;

  2. 非透明代理需要拿到解密后的HTTPS请求数据,可以通过SslSocketChannel对原始的SocketChannel做封装实现;

  3. 最后,拿到请求后,做相应的处理,最终实现非透明的代理。

3  透明上游代理

透明上游代理相比透明代理要简单,区别是

  1. 透明代理需要响应 CONNECT请求,透明上游代理不需要,直接转发即可;

  2. 透明代理需要解析CONNECT请求中的HOST和PORT,并连接服务端;透明上游代理只需要连接下游代理的IP:PORT,直接转发请求即可;

  3. 透明的上游代理,只是一个简单的SocketChannel管道;确定下游的代理服务端,连接转发请求;

只需要对透明代理做以上简单的修改,即可实现透明的上游代理。

4  非透明上游代理

非透明的上游代理,相比非透明的代理要复杂一些

代理网关设计与实现(基于NETTY)

以上,分为四个组件:客户端,代理服务(ServerHandler),代理服务(ClientHandler),服务端

  1. 如果是HTTP的请求,数据直接通过 客户端<->ServerHandler<->ClientHandler<->服务端,代理网关只需要做简单的请求聚批,就可以应用相应的管理策略;

  2. 如果是HTTPS请求,代理作为客户端和服务端的中间人,只能拿到加密的数据;因此,代理网关需要作为HTTPS的服务方与客户端通信;然后作为HTTPS的客户端与服务端通信;

  3. 代理作为HTTPS服务方时,需要考虑到其本身是个非透明的代理,需要实现非透明代理相关的协议;

  4. 代理作为HTTPS客户端时,需要考虑到其下游是个透明的代理,真正的服务方是客户端请求的服务方;

三  设计与实现

本文需要构建的是非透明上游代理,以下采用NETTY框架给出详细的设计实现。上文将统一代理网关分为两大部分,ServerHandlerClientHandler,以下

  1. 介绍代理网关服务端相关实现;

  2. 介绍代理网关客户端相关实现;

1  代理网关服务端

主要包括

  1. 初始化代理网关服务端

  2. 初始化服务端处理器

  3. 服务端协议升级与处理

初始化代理网关服务

publicvoidstart() { HookedExecutors.newSingleThreadExecutor().submit(() ->{ log.info("开始启动代理服务器,监听端口:{}", auditProxyConfig.getProxyServerPort()); EventLoopGroup bossGroup = new NioEventLoopGroup(auditProxyConfig.getBossThreadCount()); EventLoopGroup workerGroup = new NioEventLoopGroup(auditProxyConfig.getWorkThreadCount());try { ServerBootstrap b = new ServerBootstrap(); b.group(bossGroup, workerGroup) .channel(NioServerSocketChannel.class) .handler(new LoggingHandler(LogLevel.DEBUG)) .childHandler(new ServerChannelInitializer(auditProxyConfig)) .bind(auditProxyConfig.getProxyServerPort()).sync().channel().closeFuture().sync(); } catch (InterruptedException e) { log.error("代理服务器被中断.", e); Thread.currentThread().interrupt(); } finally { bossGroup.shutdownGracefully(); workerGroup.shutdownGracefully(); } }); }

代理网关初始化相对简单,

  1. bossGroup线程组,负责接收请求

  2. workerGroup线程组,负责处理接收的请求数据,具体处理逻辑封装在ServerChannelInitializer中。

代理网关服务的请求处理器在 ServerChannelInitializer中定义为

@OverrideprotectedvoidinitChannel(SocketChannel ch)throws Exception { ch.pipeline() .addLast(new HttpRequestDecoder()) .addLast(new HttpObjectAggregator(auditProxyConfig.getMaxRequestSize())) .addLast(new ServerChannelHandler(auditProxyConfig)); }

首先解析HTTP请求,然后做聚批的处理,最后ServerChannelHandler实现代理网关协议;

代理网关协议:

  1. 判定是否是CONNECT请求,如果是,会存储CONNECT请求;暂停读取,发送代理成功的响应,并在回应成功后,升级协议;

  2. 升级引擎,本质上是采用SslSocketChannel对原SocketChannel做透明的封装;

  3. 最后根据CONNECT请求连接远程服务端;

详细实现为:

@OverridepublicvoidchannelRead(ChannelHandlerContext ctx, Object msg)throws Exception { FullHttpRequest request = (FullHttpRequest)msg;try {if (isConnectRequest(request)) {// CONNECT 请求,存储待处理 saveConnectRequest(ctx, request);// 禁止读取 ctx.channel().config().setAutoRead(false);// 发送回应 connectionEstablished(ctx, ctx.newPromise().addListener(future -> {if (future.isSuccess()) {// 升级if (isSslRequest(request) && !isUpgraded(ctx)) { upgrade(ctx); }// 开放消息读取 ctx.channel().config().setAutoRead(true); ctx.read(); } })); } else {// 其他请求,判定是否已升级if (!isUpgraded(ctx)) {// 升级引擎 upgrade(ctx); }// 连接远程 connectRemote(ctx, request); } } finally { ctx.fireChannelRead(msg); } }

2  代理网关客户端

代理网关服务端需要连接远程服务,进入代理网关客户端部分。

代理网关客户端初始化:

/** * 初始化远程连接 * @param ctx * @param httpRequest */protectedvoidconnectRemote(ChannelHandlerContext ctx, FullHttpRequest httpRequest) { Bootstrap b = new Bootstrap(); b.group(ctx.channel().eventLoop()) // use the same EventLoop .channel(ctx.channel().getClass()) .handler(new ClientChannelInitializer(auditProxyConfig, ctx, safeCopy(httpRequest)));// 动态连接代理 FullHttpRequest originRequest = ctx.channel().attr(CONNECT_REQUEST).get();if (originRequest == null) { originRequest = httpRequest; } ChannelFuture cf = b.connect(new InetSocketAddress(calculateHost(originRequest), calculatePort(originRequest))); Channel cch = cf.channel(); ctx.channel().attr(CLIENT_CHANNEL).set(cch);  }

以上:

  1. 复用代理网关服务端的workerGroup线程组;

  2. 请求和结果的处理封装在ClientChannelInitializer;

  3. 连接的远程服务端的HOST和PORT在服务端收到的请求中可以解析到。

代理网关客户端的处理器的初始化逻辑:

@OverrideprotectedvoidinitChannel(SocketChannel ch)throws Exception { SocketAddress socketAddress = calculateProxy();if (!Objects.isNull(socketAddress)) { ch.pipeline().addLast(new HttpProxyHandler(calculateProxy(), auditProxyConfig.getUserName(), auditProxyConfig .getPassword())); }if (isSslRequest()) { String host = host();int port = port();if (StringUtils.isNoneBlank(host) && port > 0) { ch.pipeline().addLast(new SslHandler(sslEngine(host, port))); } } ch.pipeline().addLast(new ClientChannelHandler(clientContext, httpRequest)); }

以上:

  1. 如果下游是代理,那么会采用HttpProxyHandler,经由下游代理与远程服务端通信;

  2. 如果当前需要升级为SSL协议,会对SocketChannel做透明的封装,实现SSL通信。

  3. 最后,ClientChannelHandler只是简单消息的转发;唯一的不同是,由于代理网关拦截了第一个请求,此时需要将拦截的请求,转发到服务端。

四  其他问题

代理网关实现可能面临的问题:

1  内存问题

代理通常面临的问题是OOM。本文在实现代理网关时保证内存中缓存时当前正在处理的HTTP/HTTPS请求体。内存使用的上限理论上为实时处理的请求数量*请求体的平均大小HTTP/HTTPS的请求结果,直接使用堆外内存,零拷贝转发。

2  性能问题

性能问题不应提早考虑。本文使用NETTY框架实现的代理网关,内部大量使用堆外内存,零拷贝转发,避免了性能问题。

代理网关一期上线后面临一个长连接导致的性能问题,

  1. CLIENTSERVER建立TCP长连接后(比如,TCP心跳检测),通常要么是CLIENT关闭TCP连接,或者是SERVER关闭;

  2. 如果双方长时间占用TCP连接资源而不关闭,就会导致SOCKET资源泄漏;现象是:CPU资源爆满,处理空闲连接;新连接无法建立;

使用IdleStateHandler定时监控空闲的TCP连接,强制关闭;解决了该问题。

五  总结

本文聚焦于统一代理网关的核心,详细介绍了代理相关的技术原理。

代理网关的管理部分,可以在ServerHandler部分维护,也可以在ClientHandler部分维护;

  1. ServerHandler可以拦截转换请求

  2. ClientHanlder可控制请求的出口

注:本文使用Netty的零拷贝;存储请求以解析处理;但并未实现对RESPONSE的处理;也就是RESPONSE是直接通过网关,此方面避免了常见的代理实现,内存泄漏OOM相关问题;

最后,本文实现代理网关后,针对代理的资源和流经代理网关的请求做了相应的控制,主要包括:

  1. 当遇到静态资源的请求时,代理网关会直接请求远程服务端,不会通过下游代理

  2. 当请求HEADER中包含地域标识时,代理网关会尽力保证请求打入指定的地域代理,经由地域代理访问远程服务端

本文参考https://docs.oracle.com/javase/8/docs/technotes/guides/security/jsse/JSSERefGuide.html实现 SslSocketChannel,以透明处理HTTPHTTPS协议。

基于ELK+Flink日志全观测最佳实践

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