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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:

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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。

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多线程模式之Master-Worker模式