Step by step玩转RPC
RPC是实现SOA的基础,我在项目中多次玩过dubbo等SOA框架了,这种远程方法调用的方式不仅有趣而且有非常重要的现实意义。可以让我们把庞大的系统拆分成许多模块,每个模块又可以根据不同的压力启动不同数量的实例,模块间通过RPC透明地通信,从而将集中式的系统改造成分布式应用提高其扩展性,优化硬件资源利用率。
闲来无事,我们也来一步步手动实现RPC来感受下其中的乐趣吧。
第0步:写服务
甭管是否是远程方法调用,写两个可以调用的服务先。
很简单,一个是打招呼服务,两个方法,一个say hello,一个say byebye。另一个是计算服务,一个加,一个减。
另外,再整个简单的线程池来提高下资源利用率
第1步:socket通信实现RPC
1.服务端发布服务
分别把GreetingService注册到3456端口,CalculateService注册到6543端口。
2.客户端订阅服务
3.管理发布和订阅的框架
4.服务发布线程
服务发布的实质就是创建ServerSocket,监听服务发布的端口,当接收到请求时,根据请求中的方法名和参数动态调用方法,并把结果返回给客户端。
5.客户端代理
用动态代理模式,使得客户端调用方法的时候,实际上是建立socket连接,把方法和参数传给服务端,并接收服务端返回的结果。
运行结果
第2步:nio改写代码
上一步我们已经实现了RPC模型,不过仍有很多不足,比如我们用的是阻塞IO的方式进行的通信,因为远程方法的调用不需要建立长连接,所以用非阻塞IO的方式可以大大提高效率。
1.客户端和服务端的Customer.java和Provider.java不变,因为我们只是改变通讯方式。
2.RpcFramework.java中的publish方法需要稍加改动
在bio的方式中,我们为每个service建立一个ServerSocket,而这里,我们创建一个selector,然后为每个service创建一个channel注册到selector中,每个channel处于OP_ACCETP状态。
3.WorkThread.java修改如下
public class WorkThread implements Runnable { private Selector selector; private Map<Integer, Object> map; private final static int BLOCK = 4096; private ByteBuffer sendBuffer = ByteBuffer.allocate(BLOCK); private ByteBuffer receiveBuffer = ByteBuffer.allocate(BLOCK); public WorkThread(Selector selector, Map<Integer, Object> map) { this.selector = selector; this.map = map; } @Override public void run() { while(true) { try { selector.select(); Iterator<SelectionKey> iter = selector.selectedKeys().iterator(); while(iter.hasNext()) { SelectionKey sk = iter.next(); iter.remove(); ServerSocketChannel server = null; SocketChannel client = null; int count = 0; if(sk.isAcceptable()) { server = (ServerSocketChannel)sk.channel(); client = server.accept(); client.configureBlocking(false); client.register(selector, SelectionKey.OP_READ); } else if(sk.isReadable()) { client = (SocketChannel)sk.channel(); receiveBuffer.clear(); count = client.read(receiveBuffer); if(count > 0) { String s = new String(receiveBuffer.array(),0,count); ObjectMapper mapper = new ObjectMapper(); JsonNode node = mapper.readTree(s); String methodName = node.get("method").asText(); JsonNode ptNode = node.get("parameterType"); JsonNode pvNode = node.get("args"); Object result = null; if(ptNode.isArray() && pvNode.isArray()) { int length = ptNode.size(); Class[] paramTypes = new Class[length]; for(int i = 0; i < length; i++) { paramTypes[i] = Class.forName(ptNode.get(i).asText()); } Object[] args = new Object[length]; for(int i = 0; i < length; i++) { args[i] = pvNode.get(i).isInt()? Integer.valueOf(pvNode.get(i).asInt()): pvNode.get(i).asText(); } int port = ((InetSocketAddress)client.getLocalAddress()).getPort(); Object service = map.get(port); Method method = service.getClass().getMethod(methodName, paramTypes); result = method.invoke(service, args); } sendBuffer.clear(); sendBuffer.put(result.toString().getBytes()); sendBuffer.flip(); client.write(sendBuffer); client.register(selector, SelectionKey.OP_READ); } client.close(); sk.cancel(); } } } catch (Exception e) { e.printStackTrace(); } } }}
这里为了方便调试,使用了json字符串传递数据。
4.InvocationProxy.java修改如下
package com.rick.archi.soa.nio_tcp_rpc;import org.codehaus.jackson.map.ObjectMapper; import org.codehaus.jackson.node.ArrayNode; import org.codehaus.jackson.node.ObjectNode;import java.io.ObjectInputStream; import java.io.ObjectOutputStream; import java.lang.reflect.InvocationHandler; import java.lang.reflect.Method; import java.net.InetSocketAddress; import java.net.Socket; import java.nio.ByteBuffer; import java.nio.channels.SelectionKey; import java.nio.channels.Selector; import java.nio.channels.SocketChannel; import java.util.Iterator; import java.util.Set;public class InvocationProxy implements InvocationHandler { private String host; private int port; private final static int BLOCK = 4096; private ByteBuffer sendBuffer = ByteBuffer.allocate(BLOCK); private ByteBuffer receiveBuffer = ByteBuffer.allocate(BLOCK); public InvocationProxy(String host, int port) { this.host = host; this.port = port; } @Override public Object invoke(Object proxy, Method method, Object[] args) throws Throwable { SocketChannel sc = SocketChannel.open(); sc.configureBlocking(false); Selector selector = Selector.open(); sc.register(selector, SelectionKey.OP_CONNECT); sc.connect(new InetSocketAddress(host, port)); Iterator<SelectionKey> iterator; SelectionKey selectionKey; SocketChannel client; String result = ""; int count=0; boolean finish = false; while(!finish) { selector.select(); iterator = selector.selectedKeys().iterator(); while (iterator.hasNext()) { selectionKey = iterator.next(); if (selectionKey.isConnectable()) { client = (SocketChannel) selectionKey.channel(); if (client.isConnectionPending()) { client.finishConnect(); sendBuffer.clear(); ObjectMapper objectMapper = new ObjectMapper(); ObjectNode node = objectMapper.createObjectNode(); Class<?>[] clazz = method.getParameterTypes(); ArrayNode array1 = objectMapper.valueToTree(clazz); ArrayNode array2 = objectMapper.valueToTree(args); node.put("method", method.getName()); node.put("parameterType", array1); node.put("args", array2); String s = node.toString(); sendBuffer.put(s.getBytes()); sendBuffer.flip(); client.write(sendBuffer); } client.register(selector, SelectionKey.OP_READ); } else if (selectionKey.isReadable()) { client = (SocketChannel) selectionKey.channel(); receiveBuffer.clear(); count = client.read(receiveBuffer); if(count>0){ result = new String( receiveBuffer.array(),0,count); } finish = true; client.close(); selectionKey.cancel(); } selector.selectedKeys().clear(); }