Java实现心跳机制的方法

网友投稿 804 2022-12-01


Java实现心跳机制的方法

一、心跳机制简介

在分布式系统中,分布在不同主机上的节点需要检测其他节点的状态,如服务器节点需要检测从节点是否失效。为了检测对方节点的有效性,每隔固定时间就发送一个固定信息给对方,对方回复一个固定信息,如果长时间没有收到对方的回复,则断开与对方的连接。

发包方既可以是服务端,也可以是客户端,这要看具体实现。因为是每隔固定时间发送一次,类似心跳,所以发送的固定信息称为心跳包。心跳包一般为比较小的包,可根据具体实现。心跳包主要应用于长连接的保持与短线链接。

一般而言,应该客户端主动向服务器发送心跳包,因为服务器向客户端发送心跳包会影响服务器的性能。

二、心跳机制实现方式

心跳机制有两种实现方式,一种基于TCP自带的心跳包,TCP的SO_KEEPALIVE选项可以,系统默认的默认跳帧频率为2小时,超过2小时后,本地的TCP 实现会发送一个数据包给远程的 Socket. 如果远程Socket 没有发回响应, TCP实现就会持续尝试 11 分钟, 直到接收到响应为止。 否则就会自动断开Socket连接。但TCP自带的心跳包无法检测比较敏感地知道对方的状态,默认2小时的空闲时间,对于大多数的应用而言太长了。可以手工开启KeepAlive功能并设置合理的KeepAlive参数。

另一种在应用层自己进行实现,基本步骤如下:

Client使用定时器,不断发送心跳;

Server收到心跳后,回复一个包;

Server为每个Client启动超时定时器,如果在指定时间内没有收到Client的心跳包,则Client失效。

三、java实现心跳机制

这里基于Java实现的简单RPC框架实现心跳机制。Java实现代码如下所示:

心跳客户端类:

public class HeartbeatClient implements Runnable {

private String serverIP = "127.0.0.1";

private int serverPort = 8089;

private String nodeID = UUID.randomUUID().toString();

private boolean isRunning = true;

// 最近的心跳时间

private long lastHeartbeat;

// 心跳间隔时间

private long heartBeatInterval = 10 * 1000;

public void run() {

try {

while (isRunning) {

HeartbeatHandler handler = RPClient.getRemoteProxyObj(HeartbeatHandler.class, new InetSocketAddress(serverIP, serverPort));

long startTime = System.currentTimeMillis();

// 是否达到发送心跳的周期时间

if (startTime - lastHeartbeat > heartBeatInterval) {

System.out.println("send a heart beat");

lastHeartbeat = startTime;

HeartbeatEntity entity = new HeartbeatEntity();

entity.setTime(startTime);

entity.setNodeID(nodeID);

// 向服务器发送心跳,并返回需要执行的命令

Cmder cmds = handler.sendHeartBeat(entity);

if (!processCommand(cmds))

continue;

}

}

} catch (Exception e) {

e.printStackTrace();

}

}

private boolean processCommand(Cmder cmds) {

// ...

return true;

}

}

心跳包实体类:

public class HeartbeatEntity implements Serializable {

private long hJERKpuqLwtime;

private String nodeID;

private String error;

private Map info = new HashMap();

public String getNodeID() {

return nodeID;

}

public void setNodeID(String nodeID) {

this.nodeID = nodeID;

}

public String getError() {

return error;

}

public void setError(String error) {

this.error = error;

}

public Map getInfo() {

return info;

}

public void setInfo(Map info) {

this.info = info;

}

public long getTime() {

return time;

}

public void setTime(long time) {

this.time = time;

}

}

服务器接受心跳包返回的命令对象类:

public class Cmder implements Serializable {

private String nodeID;

private String error;

private Map info = new HashMap();

public String getNodeID() {

return nodeID;

}

public void setNodeID(String nodeID) {

this.nodeID = nodeID;

}

public String getError() {

return error;

}

public void setError(String error) {

this.error = error;

}

public Map getInfo() {

return info;

}

public void setInfo(Map info) {

this.info = info;

}

}

RPC服务注册中心:

public class ServiceCenter {

private ExecutorService executor = Executors.newFixedThreadPool(20);

private final ConcurrentHashMap serviceRegistry = new ConcurrentHashMap();

private AtomicBoolean isRunning = new AtomicBoolean(true);

// 服务器监听端口

private int port = 8089;

// 心跳监听器

HeartbeatLinstener linstener;

// 单例模式

private static class SingleHolder {

private static final ServiceCenter INSTANCE = new ServiceCenter();

}

private ServiceCenter() {

}

public static ServiceCenter getInstance() {

return SingleHolder.INSTANCE;

}

public void register(Class serviceInterface, Class impl) {

System.out.println("regeist service " + serviceInterface.getName());

serviceRegistry.put(serviceInterface.getName(), impl);

}

public void start() throws IOException {

ServerSocket server = new ServerSocket();

server.bind(new InetSocketAddress(port));

System.out.println("start server");

linstener = HeartbeatLinstener.getInstance();

System.out.println("start listen heart beat");

try {

while (true) {

// 1.监听客户端的TCP连接,接到TCP连接后将其封装成task,由线程池执行

executor.execute(new ServiceTask(server.accept()));

}

} finally {

server.close();

}

}

public void stop() {

isRunning.set(false);

executor.shutdown();

}

public boolean isRunning() {

return isRunning.get();

}

public int getPort() {

return port;

}

public void settPort(int port) {

this.port = port;

}

public ConcurrentHashMap getServiceRegistry() {

return serviceRegistry;

}

private class ServiceTask implements Runnable {

Socket clent = null;

public ServiceTask(Socket client) {

http:// this.clent = client;

}

public void run() {

ObjectInputStream input = null;

ObjectOutputStream output = null;

try {

// 2.将客户端发送的码流反序列化成对象,反射调用服务实现者,获取执行结果

input = new ObjectInputStream(clent.getInputStream());

String serviceName = input.readUTF();

String methodName = input.readUTF();

Class>[] parameterTypes = (Class>[]) input.readObject();

Object[] arguments = (Object[]) input.readObject();

Class serviceClass = serviceRegistry.get(serviceName);

if (serviceClass == null) {

throw new ClassNotFoundException(serviceName + " not found");

}

Method method = serviceClass.getMethod(methodName, parameterTypes);

Object result = method.invoke(serviceClass.newInstance(), arguments);

// 3.将执行结果反序列化,通过socket发送给客户端

output = new ObjectOutputStream(clent.getOutputStream());

output.writeObject(result);

} catch (Exception e) {

e.printStackTrace();

} finally {

if (output != null) {

try {

output.close();

} catch (IOException e) {

e.printStackTrace();

}

}

if (input != null) {

try {

input.close();

} catch (IOException e) {

e.printStackTrace();

}

}

if (clent != null) {

try {

clent.close();

} catch (IOException e) {

e.printStackTrace();

}

}

}

}

}

}

心跳监听类:

package com.cang.heartbeat;

import java.io.IOException;

import java.io.ObjectInputStream;

import java.io.ObjectOutputStream;

import java.lang.reflect.Method;

import java.net.InetSocketAddress;

import java.net.ServerSocket;

import java.net.Socket;

import java.util.Iterator;

import java.util.Map;

import java.util.concurrent.ConcurrentHashMap;

import java.util.concurrent.ExecutorService;

import java.util.concurrent.Executors;

import java.util.concurrent.atomic.AtomicBoolean;

/**

* 心跳监听保存信息

*

* @author cang

* @create_time 2016-09-28 11:40

*/

public class HeartbeatLinstener {

private ExecutorService executor = Executors.newFixedThreadPool(20);

private final ConcurrentHashMap nodes = new ConcurrentHashMap();

private final ConcurrentHashMap nodeStatus = new ConcurrentHashMap();

private long timeout = 10 * 1000;

// 服务器监听端口

private int port = 8089;

// 单例模式

private static class SingleHolder {

private static final HeartbeatLinstener INSTANCE = new HeartbeatLinstener();

}

private HeartbeatLinstener() {

}

public static HeartbeatLinstener getInstance() {

return SingleHolder.INSTANCE;

}

public ConcurrentHashMap getNodes() {

return nodes;

}

public void registerNode(String nodeId, Object nodeInfo) {

nodes.put(nodeId, nodeInfo);

nodeStatus.put(nodeId, System.currentTimeMillis());

}

public void removeNode(String nodeID) {

if (nodes.containsKey(nodeID)) {

nodes.remove(nodeID);

}

}

// 检测节点是否有效

public boolean checkNodeValid(String key) {

if (!nodes.containsKey(key) || !nodeStatus.containsKey(key)) return false;

if ((System.currentTimeMillis() - nodeStatus.get(key)) > timeout) return false;

return true;

}

// 删除所有失效节点

public void removeInValidNode() {

Iterator> it = nodeStatus.entrySet().iterator();

while (it.hasNext()) {

Map.Entry e = it.next();

if ((System.currentTimeMillis() - nodeStatus.get(e.getKey())) > timeout) {

nodes.remove(e.getKey());

http:// }

}

}

}

hJERKpuqLw

心跳处理类接口:

public interface HeartbeatHandler {

public Cmder sendHeartBeat(HeartbeatEntity info);

}

心跳处理实现类:

public class HeartbeatHandlerImpl implements HeartbeatHandler {

public Cmder sendHeartBeat(HeartbeatEntity info) {

HeartbeatLinstener linstener = HeartbeatLinstener.getInstance();

// 添加节点

if (!linstener.checkNodeValid(info.getNodeID())) {

linstener.registerNode(info.getNodeID(), info);

}

// 其他操作

Cmder cmder = new Cmder();

cmder.setNodeID(info.getNodeID());

// ...

System.out.println("current all the nodes: ");

Map nodes = linstener.getNodes();

for (Map.Entry e : nodes.entrySet()) {

System.out.println(e.getKey() + " : " + e.getValue());

}

System.out.println("hadle a heartbeat");

return cmder;

}

}

测试类:

public class HeartbeatTest {

public static void main(String[] args) {

new Thread(new Runnable() {

public void run() {

try {

ServiceCenter serviceServer = ServiceCenter.getInstance();

serviceServer.register(HeartbeatHandler.class, HeartbeatHandlerImpl.class);

serviceServer.start();

} catch (IOException e) {

e.printStackTrace();

}

}

}).start();

Thread client1 = new Thread(new HeartbeatClient());

client1.start();

Thread client2 = new Thread(new HeartbeatClient());

client2.start();

}

}

四、总结

上面的代码还有很多不足的地方,希望有空能进行改善:

配置为硬编码;

 命令类Cmder没有实际实现,返回的Cmder对象没有实际进行处理;

其他小问题就暂时不管了,希望以后能重写上面的代码。

以上就是Java实现心跳机制的方法的详细内容,更多关于Java实现心跳机制的资料请关注我们其它相关文章!


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