我想知道Tomcat 7如何实现异步处理。我知道请求线程立即返回,允许它立即监听新请求并对其做出响应。
'异步'请求是如何处理的?是否有一个独立的线程池来处理异步请求?我认为阻塞IO使用类似于java.nio.Selector的东西进行处理以获得更好的性能。那么对于在CPU计算上阻塞的线程呢?
我想知道Tomcat 7如何实现异步处理。我知道请求线程立即返回,允许它立即监听新请求并对其做出响应。
'异步'请求是如何处理的?是否有一个独立的线程池来处理异步请求?我认为阻塞IO使用类似于java.nio.Selector的东西进行处理以获得更好的性能。那么对于在CPU计算上阻塞的线程呢?
ExecutorService
并使用它进一步处理请求,或者您可以创建一个新的Runnable
并通过调用AsyncContext.start()
将其提交给获得的AsyncContext
。在Tomcat的情况下,后一种方法使用Tomcat在server.xml
中定义的线程池。 DATE THREAD_ID LEVEL MESSAGE
2011-09-03 11:51:22.198 +0200 26 I: >doGet: chrome
2011-09-03 11:51:22.204 +0200 26 I: <doGet: chrome
2011-09-03 11:51:22.204 +0200 28 I: >run: chrome
2011-09-03 11:51:27.908 +0200 29 I: >doGet: firefox
2011-09-03 11:51:27.908 +0200 29 I: <doGet: firefox
2011-09-03 11:51:32.227 +0200 28 I: <run: chrome
2011-09-03 11:51:32.228 +0200 28 I: >run: firefox
2011-09-03 11:51:42.244 +0200 28 I: <run: firefox
doGet
方法立即完成,而worker仍在运行。这2个测试请求:http://localhost:8080/pc/TestServlet?name=chrome
和http://localhost:8080/pc/TestServlet?name=firefox
。@WebServlet(asyncSupported = true, value = "/TestServlet", loadOnStartup = 1)
public class TestServlet extends HttpServlet {
private static final Logger LOG = Logger.getLogger(TestServlet.class.getName());
private static final long serialVersionUID = 1L;
private static final int NUM_WORKER_THREADS = 1;
private ExecutorService executor = null;
@Override
public void init() throws ServletException {
this.executor = Executors.newFixedThreadPool(NUM_WORKER_THREADS);
}
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
final String name = request.getParameter("name");
LOG.info(">doGet: " + name);
AsyncContext ac = request.startAsync(); // obtain async context
ac.setTimeout(0); // test only, no timeout
/* Create a worker */
Runnable worker = new TestWorker(name, ac);
/* use your own executor service to execute a worker thread (TestWorker) */
this.executorService.execute(worker);
/* OR delegate to the container */
// ac.start(worker);
LOG.info("<doGet: " + name);
}
}
...and the TestWorker
public class TestWorker implements Runnable {
private static final Logger LOG = Logger.getLogger(TestWorker.class.getName());
private final String name;
private final AsyncContext context;
private final Date queued;
public TestWorker(String name, AsyncContext context) {
this.name = name;
this.context = context;
this.queued = new Date(System.currentTimeMillis());
}
@Override
public void run() {
LOG.info(">run: " + name);
/* do some work for 10 sec */
for (int i = 0; i < 100; i++) {
try {
Thread.sleep(100);
} catch (InterruptedException e) {
throw new RuntimeException(e);
}
}
ServletResponse response = this.context.getResponse();
response.setContentType("text/plain");
try {
PrintWriter out = response.getWriter();
out.println("Name:\t\t" + this.name);
out.println("Queued:\t\t" + this.queued);
out.println("End:\t\t" + new Date(System.currentTimeMillis()));
out.println("Thread:\t\t" + Thread.currentThread().getId());
out.flush();
} catch (IOException e) {
throw new RuntimeException(e);
}
this.context.complete();
LOG.info("<run: " + name);
}
}