云智慧（北京）科技有限公司 陈鑫
重启线程池
TaskManager
public class TaskManager implements Runnable {
…..
public TaskManager (Set<FileTask>runners) {
super();
this.runners = runners;
executeTasks(runners);
}
private voidexecuteTasks(Set<FileTask> runners) {
for (FileTask task : runners){
pool.execute(task);
System.out.println(task.getClass().getSimpleName() + " has beenstarted");
}
}
@Override
public void run() {
while(!Thread.currentThread().isInterrupted()) {
try {
long current = System.currentTimeMillis();
for (FileTask wrapper : runners) {
if (wrapper.getLastExecTime() != 0 && current -wrapper.getLastExecTime() > wrapper.getInterval() * 5 * 1000) { // 开始忘了乘以1000
wrapper.interrupt();
if (wrapper.getFiles() != null){
for (File file : wrapper.getFiles()){
file.delete();
}
}
System.out.println("Going to shutdown thethread pool");
List<Runnable> shutdownNow = pool.shutdownNow(); // 不等当前pool里的任务执行完，直接关闭线程池
for (Runnable run : shutdownNow) {
System.out.println(run + " goingto be shutdown");
}
while (pool.awaitTermination(1, TimeUnit.SECONDS)) {
System.out.println("The threadpool has been shutdown " + new Date());
executeTasks(runners);//重新执行
Thread.sleep(200);
}
}
}
} catch(Exception e1) {
e1.printStackTrace();
}
try {
Thread.sleep(500);
} catch(InterruptedException e) {
}
}
}
public static void main(String[] args) {
Set<FileTask> tasks =new HashSet<FileTask>();
FileTask task = newFileTask();
task.setInterval(1);
task.setName("task-1");
tasks.add(task);
FileTask task1 = newFileTask();
task1.setInterval(2);
task.setName("task-2");
tasks.add(task1);
TaskManager codeManager = new TaskManager (tasks);
newThread(codeManager).start();
}
}
成功！把整个的ThreadPoolExector里所有的worker全部停止，之后再向其队列里重新加入要执行的两个task（注意这里并没有清空，只是停止而已）。这样做虽然能够及时处理task，但是一个很致命的缺点在于，如果不能明确的知道ThreadPoolExecutor要执行的task，就没有办法重新执行这些任务。
定制线程池
好吧!停止钻研别人的东西！我们完全可以自己写一个自己的ThreadPoolExecutor，只要把worker暴露出来就可以了。这里是不是回想起前面的start问题来了，没错，我们即便能够直接针对Thread进行interrupt, 但是不能再次start它了。那么clone一个同样的Thread行不行呢？
Thread
@Override
protectedObject clone() throws CloneNotSupportedException{
throw newCloneNotSupportedException();
}
答案显而易见，线程是不支持clone 的。我们需要重新new 一个Thread来重新运行。其实我们只需要将原来的Worker里的Runnable换成我们自己的task，然后将访问权限适当放开就可以了。还有，就是让我们的CustomThreadPoolExecutor继承Thread，因为它需要定时监控自己的所有的worker里Thread的运行状态。
CustomThreadPoolExecutor
public class CustomThreadPoolExecutor extendsThreadPoolExecutor implements Runnable {
public voidexecute(Testask command) {
….//将执行接口改为接收我们的业务类
}
…
…
private final class Worker
extends AbstractQueuedSynchronizer
implements Runnable
{
…
Testask firstTask; //将Runnable改为我们的业务类，方便查看状态
…
Worker(Testask firstTask) {
…//同样将初始化参数改为我们的业务类
}
}
public staticvoid main(String[] args) {
CustomThreadPoolExecutor pool = new CustomThreadPoolExecutor(0, Integer.MAX_VALUE,
60L, TimeUnit.SECONDS,
newSynchronousQueue<Runnable>());
Testasktask = new Testask();
task.setInterval(1);
pool.execute(task);
Testasktask1 = new Testask();
task1.setInterval(2);
pool.execute(task1);
newThread(pool).start();
}
@Override
public voidrun() {
while(!Thread.currentThread().isInterrupted()) {
try {
long current = System.currentTimeMillis();
Set<Testask> toReExecute = new HashSet<Testask>();
System.out.println(" number is " + number);
for(Worker wrapper : workers) {
Testask tt = wrapper.firstTask;
if (tt != null) {
if (current - tt.getLastExecTime() > tt.getInterval() * 5 * 1000) {
wrapper.interruptIfStarted();
remove(tt);
if (tt.getFiles() != null) {
for (File file: tt.getFiles()) {
file.delete();
}
}
System.out.println("THread is timeout : " + tt + " "+ new Date());
toReExecute.add(tt);
}
}
}
if(toReExecute.size() > 0) {
mainLock.lock();
try {
for (Testask tt :toReExecute) {
execute(tt); // execute this task again
}
} finally {
mainLock.unlock();
}
}
} catch(Exception e1) {
System.out.println("Error happens when we trying to interrupt andrestart a code task ");
}
try {
Thread.sleep(500);
} catch(InterruptedException e) {
}
}
}
}
Testask
class Testask implements Runnable {
…..
@Override
public voidrun() {
while(!Thread.currentThread().isInterrupted()) {
lastExecTime = System.currentTimeMillis();
System.out.println(Thread.currentThread().getName() + " is running-> " + new Date());
try {
CustomThreadPoolExecutor.number++;
Thread.sleep(getInterval() * 6 * 1000);
System.out.println(Thread.currentThread().getName() + " aftersleep");
} catch(InterruptedException e) {
Thread.currentThread().interrupt();
System.out.println("InterruptedException happens");
}
}
System.out.println("Going to die");
}
}
最终方案
综上，最稳妥的就是使用JDK自带的ThreadPoolExecutor,如果需要对池里的task进行任意时间的控制，可以考虑全面更新，全方面，360度无死角的定制自己的线程池当然是最好的方案，但是一定要注意对于共享对象的处理，适当的处理好并发访问共享对象的方法。
鉴于我们的场景，由于时间紧，而且需要了解的task并不多，暂时选用全部重新更新的策略。上线后，抽时间把自己定制的ThreadPoolExecutor搞定，然后更新上去！