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多线程模式之Master-Worker模式
Master-Worker模式的核心思想是,系统由两类进程协作工作:Master进程和Worker进程。Master进程负责接收和分配任 务,Worker进程负责处理子任务。当Worker进程将各个子任务处理完成后,将结果返回给Master进程,由Master进程做归纳和汇总。
工作示意图如下图所示:
它的优势在于将一个大的任务分解成一个个的子任务并行执行,提高程序执行效率。
代码示例:
Master进程类:
public class Master {
protected Queue<Object> workQueue = new ConcurrentLinkedQueue<Object>();//存放子任务
protected Map<String,Thread> threadMap = new HashMap<String,Thread>();//存放Worker线程
protected Map<String,Object> resultMap = new ConcurrentHashMap<String, Object>();//存放返回结果集
public boolean isCompleted(){
for(Map.Entry<String,Thread> entry:threadMap.entrySet()){
if(entry.getValue().getState() != Thread.State.TERMINATED){
return false;
}
}
return true;
}
public Master(Worker worker,int countWorker){
worker.setWorkQueue(workQueue);
worker.setResultMap(resultMap);
for(int i=0;i<countWorker;i++){//创建多个Worker线程
threadMap.put(Integer.toString(i),new Thread(worker,Integer.toString(i)));
}
}
public void submit(Object job){
workQueue.add(job);//将任务加到子任务队列中
}
public Map<String,Object> getResultMap(){
return resultMap;
}
public void execute(){
//循环启动Worker线程
for(Map.Entry<String,Thread> entry:threadMap.entrySet()){
entry.getValue().start();
}
}
}
Worker进程类:
public class Worker implements Runnable{
protected Queue<Object> workQueue;
protected Map<String,Object> resultMap;
public void setWorkQueue(Queue<Object> workQueue){
this.workQueue = workQueue;
}
public void setResultMap( Map<String,Object> resultMap){
this.resultMap = resultMap;
}
public Object handle(Object input){
return input;
}
public void run(){
while(true){
Object input = workQueue.poll();//从子任务中取任务执行
if(input == null) break;
Object re = handle(input);//这是一个模板方法模式
resultMap.put(Integer.toString(input.hashCode()),re);
}
}
}
PlusWorker进程类:
public class PlusWorker extends Worker {
public Object handle(Object input){
Integer i = (Integer)input;
return i*i*i;
}
}
测试类:
public class Main {
public static void main(String[] args){
Master m = new Master(new PlusWorker(),5);
for(int i=0;i<100;i++)
m.submit(i);
m.execute();
int re = 0;
Map<String,Object> resultMap = m.getResultMap();
while(resultMap.size() >0 || !m.isCompleted()){
Set<String> keys = resultMap.keySet();
String key = null;
for(String k:keys){
key = k;
break;
}
Integer i = null;
if(key != null)
i = (Integer)resultMap.get(key);
if(i != null)
re += i;
if(key != null)
resultMap.remove(key);
}
System.out.println("re:"+re);
}
}
Main不用等所有的Worker线程都计算完以后再执行,只要有计算完成的,它就一直计算。
- 本文来自:Linux教程网
多线程模式之Master-Worker模式