```java package algorithm.loadbalance;
import com.alibaba.fastjson.JSON;
import java.util.*;
/**
@author Cao Xuan
@date 2021/3/21 20:04
@update 2021/5/5 */ public class LoadBalanceDemo {
private final List serverList = new ArrayList<>();
/**
client -> server */ private final Map<Client, Server> clientServerMap = new HashMap<>(); /**
<—head—tail—> <—light—weight—> <—former—latter–> */ @Deprecated private void sort() { for (int i = serverList.size() - 1; i > 0; i–) { for (int j = i - 1; j > -1; j–) { Server latter = new Server(serverList.get(i)); Server former = new Server(serverList.get(j)); if (latter.getCurrentLoad().size() > former.getCurrentLoad().size()) { serverList.set(i, former); serverList.set(j, latter); } } } System.out.println(“sorting…”); } /**
<—head—tail—> <—light—weight—> <—former—latter–> */ private void leafShift() { int size = serverList.size(); for (int i = size - 2; i >= 0; i–) { Server latter = new Server(serverList.get(size - 1)); Server former = new Server(serverList.get(i)); if (latter.getCurrentLoad().size() > former.getCurrentLoad().size()) { serverList.set(size - 1, former); serverList.set(i, latter); System.out.println(“leaf shift”); } } } private void rightShift(int index) { int size = serverList.size(); for (int i = index + 1; i < size; i++) { Server former = new Server(serverList.get(index)); Server latter = new Server(serverList.get(i)); if (former.getCurrentLoad().size() < latter.getCurrentLoad().size()) { serverList.set(i, former); serverList.set(index, latter); System.out.println(“right shift”); } } }
public Server addClient(Client client) { if (serverList.size() > 0) { Server server = new Server(serverList.get(serverList.size() - 1)); String serverName = server.getName(); serverList.get(serverList.size() - 1).updateCurrentLoad(client); System.out.println(“Hi,[” + client.getUsername() + “]. Assign [” + serverName + “] to you”); leafShift(); show(); return server; } else { System.err.println(“no server”); return null; } }
public void removeClient(String clientName) { Server server = clientServerMap.get(new Client(clientName)); int index = serverList.indexOf(server); if (-1 != index) { server.currentLoad.remove(new Client(clientName)); rightShift(index); System.out.println(“remove a client [” + clientName + “]”); } else { System.err.println(“index = -1”); }
show(); }
public void addServer(String name) { Server server = new Server(name, new HashSet<>()); if (serverList.contains(server)) { System.err.println(“The server [” + name + “] already exists”); show(); return; } serverList.add(server); System.out.println(“add a server [” + name + “]”); show(); }
public void removeServer(String serverName) { serverList.remove(new Server(serverName)); System.out.println(“add a server [” + serverName + “]”); show(); }
private static class Client {
private String username; public Client(String username) { this.username = username; } public String getUsername() { return username; } public void setUsername(String username) { this.username = username; } @Override public boolean equals(Object obj) { if (!(obj instanceof Client)) { return false; } Client client = (Client) obj; return this.getUsername().equals(client.getUsername()); } @Override public int hashCode() { return Objects.hash(username); } @Override public String toString() { return JSON.toJSONString(this); } }
private static class Server {
private String name; private Set<Client> currentLoad; public Server(String name) { this.name = name; } public Server(Server server) { this.name = server.name; this.currentLoad = server.currentLoad; } public Server(String name, Set<Client> currentLoad) { this.name = name; this.currentLoad = currentLoad; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Set<Client> getCurrentLoad() { return currentLoad; } public void setCurrentLoad(Set<Client> currentLoad) { this.currentLoad = currentLoad; } public void updateCurrentLoad(Client client) { this.currentLoad.add(client); } @Override public boolean equals(Object obj) { if (!(obj instanceof Server)) { return false; } Server server = (Server) obj; return this.getName().equals(server.getName()); } @Override public String toString() { return JSON.toJSONString(this); } }
public static void main(String[] args) {
LoadBalanceDemo loadBalanceDemo = new LoadBalanceDemo(); System.out.println("---------------USAGE--------------"); System.out.println("Add a server: [s+${serverName}]"); System.out.println("Add a client: [c+${clientName}]"); System.out.println("Remove a server: [s-${serverName}]"); System.out.println("Remove a client: [c-${clientName}]"); System.out.println("Show Current Load: [show]"); System.out.println("---------------USAGE--------------"); while (true) { System.out.println("ready"); System.out.println(); Scanner scanner = new Scanner(System.in); String s = scanner.next(); if ("show".equals(s)) { loadBalanceDemo.show(); } else if (s.startsWith("c+")) { String clientName = s.substring(2); Client client = new Client(clientName); Server server = loadBalanceDemo.addClient(client); loadBalanceDemo.clientServerMap.put(client, server); } else if (s.startsWith("s+")) { String serverName = s.substring(2); loadBalanceDemo.addServer(serverName); } else if (s.startsWith("c-")) { String clientName = s.substring(2); loadBalanceDemo.removeClient(clientName); } else if (s.startsWith("s-")) { String serverName = s.substring(2); loadBalanceDemo.removeServer(serverName); } else { System.out.println("?"); } System.out.println("----------------------------------"); } }
private void show() { System.out.println(“current load " + serverList); } }
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