Java之RPC高性能框架概述

1. RPC

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RPC定义


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自定义RPC框架的设计思路

这个框架需要的知识点:socket、zookeeper、动态代理、反射、spring

这个框架的socketServer部分,之前学习的demo程序只是一个基础,这里需要更高级的netty nio


2. NIO-New IO

2.1. 定义

nio是New IO的简称,从jdk1.4开始提供的新的api包。特性:为所有的原始类型提供buffer缓存支持,字符集编码解码解决方案。

channel:一个新的原始I/O抽象。

支持锁和内存映射文件的文件访问接口。提供多路non-blocking非阻塞式的高伸缩性网络IO。


2.2. socket nio原理

2.2.1. 传统的I/O

传统I/O程序读取文件内容,写到另一个文件或socket:

File.read(fileDesc, buf, len);

Socket.send(socket, buf, len);

以上是传统IO做法,会有较大性能开销,主要表现在两个方面:

1. 上下文切换(context switch), 此处有4次用户态和内核态的切换

2. Buffer内存开销,一个是应用程序buffer,另一个是系统读取buffer以及socket buffer其运行示意图如下

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1)先将文件内容从磁盘中拷贝到操作系统buffer

2)再从OS buffer拷贝到程序应用buffer

3)从程序buffer拷贝到socket buffer

4)从socket buffer拷贝到协议引擎


2.2.2. NIO

NIO技术相比传统IO技术,省去了上面步骤2)、3),直接将read buffer拷贝到socket buffer。FileChannel.transferTo() 方法就是这样的实现,这个实现是依赖于OS底层的sendFile()实现的。

如下图:

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2.2.3. 传统IO和NIO服务器端对比

传统IO服务器端如果有多个客户端连接,服务器每accept一个客户端,都会创建一个Thread去跟客户端通信。这样看起来服务器端是没有阻塞的,实际上服务器端是阻塞的,是一个伪异步方式的IO,阻塞在accept。如下图:

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NIO是使用select方式,接收linux kernel的消息通知模式来处理多客户端的连接和消息收发。如下图:

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原始NIO demo代码结构如下:

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服务器端:

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服务器端主程序

public class MultiplexerTimeServer implements Runnable{

private Selector selector;

private ServerSocketChannel servChannel;

private volatile boolean stop;

public MultiplexerTimeServer(int port){

try {

selector = Selector.open();

servChannel = ServerSocketChannel.open();

servChannel.configureBlocking(false);

servChannel.socket().bind(new InetSocketAddress(port), 1024);

servChannel.register(selector,  SelectionKey.OP_ACCEPT);

} catch (IOException e) {

e.printStackTrace();

}

out.println("The time server is start in port : " + port);

}

public void stop(){

this.stop = true;

}

@Override

public void run() {

while(!stop){

try {

selector.select(1000);

Set selectedKeys = selector.selectedKeys();

Iterator it = selectedKeys.iterator();

SelectionKey key = null;

while(it.hasNext()){

key = it.next();

it.remove();

handleInput(key);

if(key != null){

key.cancel();

if (key.channel() != null){

key.channel().close();

}

}

}

} catch (IOException e) {

e.printStackTrace();

}

}

if(selector != null){

try {

selector.close();

} catch (IOException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

}

}

private void handleInput(SelectionKey key) throws IOException{

if(key.isValid()){

//process the new connection

if(key.isAcceptable()){

//accept the new connection

ServerSocketChannel ssc = (ServerSocketChannel) key.channel();

SocketChannel sc = ssc.accept();

sc.configureBlocking(false);

//add the new connection to the selector

sc.register(selector, SelectionKey.OP_READ);

}

if(key.isReadable()){

//read the data

SocketChannel sc = (SocketChannel) key.channel();

ByteBuffer readBuffer = ByteBuffer.allocate(1024);

int readBytes = sc.read(readBuffer);

if (readBytes > 0){

readBuffer.flip();

byte[] bytes = new byte[readBuffer.remaining()];

readBuffer.get(bytes);

String body = new String(bytes, "UTF-8");

out.println("The time server receive order : " + body);

String currentTime = "QUERY TIME ORDER".equalsIgnoreCase(body) ? new java.util.Date(System.currentTimeMillis()).toString() : "BAD ORDER";

doWrite(sc, currentTime);

}else if(readBytes < 0){

//client is disconnect

key.cancel();

sc.close();

}else{

//read 0 byte do nothing

;

}

}

}

}

private void doWrite(SocketChannel channel, String response) throws IOException{

if(response != null && response.trim().length() > 0){

byte[] bytes = response.getBytes();

ByteBuffer writeBuffer = ByteBuffer.allocate(bytes.length);

writeBuffer.put(bytes);

writeBuffer.flip();

channel.write(writeBuffer);

}

}

}


客户端:

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客户端主程序

public class TimeClientHandle implements Runnable{

private String host;

private int port;

private Selector selector;

private SocketChannel socketChannel;

private volatile boolean stop;

public TimeClientHandle(String host, int port) {

this.host = host == null ? "127.0.0.1" : host;

this.port = port;

try {

selector = Selector.open();

socketChannel = SocketChannel.open();

socketChannel.configureBlocking(false);

} catch (IOException e) {

e.printStackTrace();

System.exit(1);

}

}

@Override

public void run() {

try {

doConnect();

} catch (IOException e2) {

// TODO Auto-generated catch block

e2.printStackTrace();

}

while(!stop){

try {

selector.select(1000);

Set selectedKeys = selector.selectedKeys();

Iterator it = selectedKeys.iterator();

SelectionKey key = null;

while(it.hasNext()){

key = it.next();

it.remove();

try{

handleInput(key);

}catch(Exception e){

if(key != null){

key.cancel();

if(key.channel() != null){

key.channel().close();

}

}

}

}

} catch (IOException e1) {

e1.printStackTrace();

System.exit(1);

}

}

if(selector != null){

try {

selector.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

private void doConnect() throws IOException{

if(socketChannel.connect(new InetSocketAddress(host, port))){

socketChannel.register(selector,  SelectionKey.OP_READ);

doWrite(socketChannel);

}else{

socketChannel.register(selector,  SelectionKey.OP_CONNECT);

}

}

private void doWrite(SocketChannel sc) throws IOException{

byte[] req = "Query Time Order".getBytes();

ByteBuffer writeBuffer = ByteBuffer.allocate(req.length);

writeBuffer.put(req);

writeBuffer.flip();

sc.write(writeBuffer);

if(!writeBuffer.hasRemaining()){

out.println("Send order 2 server succeed.");

}

}

private void handleInput(SelectionKey key) throws IOException{

if (key.isValid()){

//check if connet succ

SocketChannel sc = (SocketChannel) key.channel();

if(key.isConnectable()){

if(sc.finishConnect()){

sc.register(selector, SelectionKey.OP_READ);

doWrite(sc);

}else{

System.exit(1); //connect error

}

}

if(key.isReadable()){

ByteBuffer readBuffer = ByteBuffer.allocate(1024);

int readBytes = sc.read(readBuffer);

if (readBytes > 0){

readBuffer.flip();

byte[] bytes = new byte[readBuffer.remaining()];

readBuffer.get(bytes);

String body = new String(bytes, "UTF-8");

out.println("Now is : " + body);

this.stop = true;

}else if(readBytes < 0){

key.cancel();

sc.close();

}else{

;

}

}

}

}

}


2.3. 高性能NIO框架netty

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