Tomcat 7异步处理
Tomcat 7异步处理
提问于 2011-09-03 01:39:06
我想知道Tomcat7是如何实现异步处理的。我知道请求线程会立即返回，允许请求线程立即侦听新请求并对其进行响应。
“异步”请求是如何处理的？是否有单独的线程池来处理异步请求？为了提高性能，我假设阻塞IO是使用类似于java.nio.Selector的东西来处理的。在CPU计算中阻塞的线程怎么办？
回答 1
Stack Overflow用户
回答已采纳
发布于 2011-09-03 20:29:36
你混淆了不同的概念。您必须区分以下各项：
按照Servlet3.0API处理
- Asynchronous请求；使您能够将传入的Servlet请求从web容器线程池中解耦出来的。它不会在运行时创建任何线程。接口的用户需要实现一个适当的多线程解决方案。它与非阻塞IO.
- Thread池无关；提供了一种在web容器中获取和管理线程的机制。当涉及到异步请求处理时，您有两个选择。您可以定义自己的
ExecutorService并使用它来进一步处理请求，也可以创建一个新的Runnable并通过调用AsyncContext.start()将其提交给获得的AsyncContext。对于Tomcat线程池，后一种方法使用在NIO(server.xml. - Non-blocking )中定义的Tomcat线程池；尽管它也是异步的，但却是另一回事。它与磁盘或网络IO等非阻塞IO操作相关。如果希望为HTTP请求处理启用NIO，可以查看Tomcat的documentation.
下面的示例概述了它的工作原理。它只使用一个线程来处理工作任务。如果你从两个不同的浏览器并行运行它，输出如下所示(我使用一个自定义记录器)：
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您会看到doGet方法立即结束，而worker仍在运行。2个测试请求：http://localhost:8080/pc/TestServlet?name=chrome和http://localhost:8080/pc/TestServlet?name=firefox。
简单示例Servlet
@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);
}
}页面原文内容由Stack Overflow提供。腾讯云小微IT领域专用引擎提供翻译支持
原文链接：
https://stackoverflow.com/questions/7287244
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