在线程池中寻找堆栈
下面看一个简单的例子:
public class DivTask implements Runnable {
int a, b;
public DivTask(int a, int b) {
this.a = a;
this.b = b;
}
@Override
public void run() {
double re = a / b;
System.out.println(re);
}
}
运行该任务:
public static void main(String[] args) {
ThreadPoolExecutor pools = new ThreadPoolExecutor(0, Integer.MAX_VALUE,
0L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>());
for (int i = 0; i < 5; i++) {
pools.submit(new DivTask(100, i));
}
}
可以得到:
100.0
25.0
33.0
50.0
只有4个输出,也就是说程序漏算了一组数据,并且程序没有任何日志,没有任何错误提示.
解决上述问题最简单的一种方法就输出放弃submit(),改用execute()
pools.execute(new DivTask(100, i));
或者使用
Future submit = pools.submit(new DivTask(100, i));
submit.get();
上面两种方法都可以得到部分堆栈信息,如下所示:
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
at threadDemo.DivTask.run(DivTask.java:19)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
100.0
25.0
33.0
50.0
这里只能知道异常是在哪里抛的,并不知道是在哪里提交的,所以我们扩展我们的ThreadPoolExecutor线程池
/**
* @author luozhiyun on 2018/6/25.
*/
public class TraceThreadPoolExecutor extends ThreadPoolExecutor {
public TraceThreadPoolExecutor(int corePoolSize, int maximumPoolSize,
long keepAliveTime, TimeUnit unit, BlockingQueue<Runnable> workQueue) {
super(corePoolSize, maximumPoolSize, keepAliveTime, unit, workQueue);
}
@Override
public void execute(Runnable command) {
super.execute(wrap(command,clientTrace(),Thread.currentThread().getName()));
}
@Override
public Future<?> submit(Runnable task) {
return super.submit(wrap(task, clientTrace(), Thread.currentThread().getName()));
}
private Exception clientTrace() {
return new Exception("Client stack trace");
}
private Runnable wrap(final Runnable task, final Exception clientStack, String clientThreadName) {
return new Runnable() {
@Override
public void run() {
try {
task.run();
} catch (Exception e) {
clientStack.printStackTrace();
throw e;
}
}
};
}
public static void main(String[] args) {
ThreadPoolExecutor pools = new TraceThreadPoolExecutor(0, Integer.MAX_VALUE,
0L, TimeUnit.SECONDS,
new SynchronousQueue<Runnable>());
for (int i = 0; i < 5; i++) {
pools.execute(new DivTask(100, i));
}
}
}
通过上面扩展的线程池, 就可以打印出堆栈信息了
100.0
25.0
33.0
50.0
java.lang.Exception: Client stack trace
at threadDemo.TraceThreadPoolExecutor.clientTrace(TraceThreadPoolExecutor.java:25)
at threadDemo.TraceThreadPoolExecutor.execute(TraceThreadPoolExecutor.java:16)
at threadDemo.TraceThreadPoolExecutor.main(TraceThreadPoolExecutor.java:48)
Exception in thread "pool-1-thread-1" java.lang.ArithmeticException: / by zero
at threadDemo.DivTask.run(DivTask.java:19)
at threadDemo.TraceThreadPoolExecutor$1.run(TraceThreadPoolExecutor.java:33)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at java.lang.Thread.run(Thread.java:748)
Process finished with exit code 0
现在我们不仅可以得到异常发生的Runnable实现内的信息,我们也知道了这个任务是在哪里提交的.