Jetty Continuation - 이상민

목차 1. Current WAS 2. Jetty Continuation 3. Jetty Continuation sample & demo 4. Servlet 3.0

1. Current WAS (Based on Servlet spec. 2.5)

1.1 Thread Pool • Whenever we request, WAS always doesn’t make new thread.  It uses Thread Pool. • It’s not easy to set suitable Thread Pool size. • Thread per connection • The traditional IO model of java associates a thread with every TCP/IP connection. 4 / Jetty Continuation

1.2 Synchronous • Almost all web requests are handled synchronously. • Asynchronous request handling on WAS is not easy. 5 / Jetty Continuation

1.3 AJAX polling problem • AJAX servers cannot deliver asynchronous events to the client, the AJAX client must poll for events on the server. • To avoid a busy polling loop, AJAX servers will often hold onto a poll request until either there is an event or a timeout occurs. • The server again needs to have one or more threads for every client. http://docs.codehaus.org/display/JETTY/Continuations 6 / Jetty Continuation

2. Jetty Continuation 7 / Jetty Continuation

2.1.1 What is Jetty • Jetty - http://eclipse.org/jetty/ • Jetty provides an HTTP server, HTTP client, and javax.servlet container. • Full-featured and standards-based • Open source and commercially usable • Flexible and extensible • Small footprint • Embeddable • Asynchronous • Enterprise scalable • Dual licensed under Apache and Eclipse 8 / Jetty Continuation

2.1.2 Asynchronous Servlet • Asynchronous Servlets • Not Asynchronous IO • Asynchronous Servlets are different with Asynchronous IO or the use of NIO • Asynchronous Waiting • waiting for a resource to be available before processing the request • waiting for an application event in an AJAX Comet application • waiting for a response from a remote service 9 / Jetty Continuation

2.1.3 Continuation • Continuation in Naver dictionary 10 / Jetty Continuation

2.1.3 Continuation • Continuation in Jetty • A continuation is a mechanism by which a HTTP Request can be suspended and restarted after a timeout or an asynchronous event has occurred. 11 / Jetty Continuation

2.1.2 Continuation • Continuation • Process of continuation Registered with an async. service Working in other thread Return thread Take thread 12 / Jetty Continuation

2.2.1 Thread Pool with Continuation • You also should use Thread Pool when you use Continuation • But you can manage WAS with a fewer Thread. 13 / Jetty Continuation

2.2.2 Use Asynchronous call with Continuation • You must use “Asynchronous call” to use Continuation • One thread can run much request at a time. 14 / Jetty Continuation

2.2.3 Continuation examples • Chat Servlet • http://download.eclipse.org/jetty/stable- 7/xref/com/acme/ChatServlet.html • Jetty’s filter & servlet • QoSFilter (Quality of Service Filter) • DosFilter (Denial of Service Filter) • GzipFilter (Compress response objects) • ProxyServlet 15 / Jetty Continuation

2.3 Continuation sample • Continuation sample public class ContinuationServlet extends HttpServlet{ public void service(HttpServletRequest req, HttpServletResponse res) throws IOException { String flag=(String)req.getAttribute("CONT_FLAG"); if(flag==null) { Continuation continuation = ContinuationSupport.getContinuation(req); continuation.addContinuationListener(new AListener()); continuation.setTimeout(5000); continuation.suspend(); req.setAttribute("CONT_FLAG", "RUNNING"); //asynchronous call } else { } Call resume() or complete(), return; after work is done. } 16 / Jetty Continuation

2.4 Continuation interface • Continuation interface • Package : org.eclipse.jetty.continuation • Methods : • setTimeout(long) • addContinuationListener(ContinuationListener) • suspend(), suspend(ServletResponse) • resume() • complete() … 17 / Jetty Continuation

2.4 Continuation interface • Continuation interface • Get instance of Continuation Continuation continuation= ContinuationSupport.getContinuation(request); 18 / Jetty Continuation

2.5.1 Continuation.setTimeout (long) • setTimeout(long timeoutMS) method • Set the continuation timeout. • You can set timeout in millisecond(1/1000 second) unit. • If timeoutMS is <=0, the continuation will never expire. (Don’t do that - -) Sample code //set timeout 5 seconds continuation.setTimeout(5000); 19 / Jetty Continuation

2.5.2.1 Continuation. addContinuationListener(ContinuationListener ) • addContinuationListener(ContinuationListener) method • Add a ContinuationListener • You can handle continuation result by ContinuationListener Sample code //Make listener class SampleListener listener=new SampleListener(); //Add listener to continuation object continuation.addContinuationListener(listener); 20 / Jetty Continuation

2.5.2.2 How can I make ContinuationListener? • Just implements ContinuationListener interface with two methods Sample code import org.eclipse.jetty.continuation.Continuation; import org.eclipse.jetty.continuation.ContinuationListener; public class SampleListener implements ContinuationListener{ public SampleListener() { } When Continuation is completed public void onComplete(Continuation continuation) { } public void onTimeout(Continuation continuation) { } } When Continuation is timeout 21 / Jetty Continuation

2.5.3 Continuation.suspend() • suspend() & suspend(ServletResponse) method • Suspend the processing of the request and associated ServletResponse. • After this method has been called, the lifecycle of the request will be extended beyond the return to the container from • Servlet.service(ServletRequest, ServletResponse) • Filter.doFilter(ServletRequest, ServletResponse, FilterChain) calls. 22 / Jetty Continuation

2.5.3 Continuation.suspend() • suspend() & suspend(ServletResponse) method • The thread is freed for other tasks and the request is held until • a call to resume(). • a call to complete(). • the timeout expires. Sample code continuation.suspend(); or continuation.suspend(response); 23 / Jetty Continuation

2.5.4 Continuation.resume() • resume() method • Resume a suspended request. • The request is redispatched to the normal filter chain and servlet processing with isInitial() false. • Typically resume() is used after a call to suspend() with no arguments. 24 / Jetty Continuation

2.5.5 Continuation.complete() • complete() method • Complete a suspended request. • The associated response object committed and flushed. The request is not redispatched. • Typically complete() is used after a call to suspend(ServletResponse) with a possibly wrapped response. 25 / Jetty Continuation

2.5.5 resume() vs complete() • compare resume() vs complete() methods resume() complete() redispatch O X suspend type suspend() suspend(ServletResponse) wrap response X O 26 / Jetty Continuation

2.6 Asynchronous on Java • Use java.lang.Thread • Easy to use • But making new thread every time is not good in performance • Use java.util.concurrent.ExecutorService • Not easy to use at first time. • But it reuse threads and manages thread pool. 27 / Jetty Continuation

2.6 Asynchronous on Java • Thread sample package com.cont.sample.async; public class ThreadSample extends Thread { public static void main(String args[]) { ThreadSample sample=new ThreadSample(); System.out.println("Before start sample."); Before start sample. sample.start(); After start sample. System.out.println("After start sample."); Run method called } public void run() { System.out.println("Run method called"); } } 28 / Jetty Continuation

2.6 Asynchronous on Java • Executor sample package com.cont.sample.async.executor; public class SampleReceiver { public void receiveResult(Object obj) { System.out.println("Received result is "+obj); } } package com.cont.sample.async.executor; import java.util.concurrent.Callable; public class SampleCallable implements Callable<Object>{ private SampleReceiver receiver; public SampleCallable(SampleReceiver receiver) { this.receiver=receiver; } public Object call() throws Exception { System.out.println("SampleCallable is called"); receiver.receiveResult("OK"); return null; } } 29 / Jetty Continuation

2.6 Asynchronous on Java • Executor sample – execute package com.cont.sample.async.executor; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; public class ExecutorMain { public static void main(String[] args) { ExecutorService service= Executors.newCachedThreadPool(); Before submit After submit SampleReceiver receiver= SampleCallable is called new SampleReceiver(); Received result is OK SampleCallable callable= new SampleCallable(receiver); System.out.println("Before submit"); service.submit(callable); System.out.println("After submit"); } } 30 / Jetty Continuation

3. Jetty Continuation sample & demo 31 / Jetty Continuation

3.1 Common Servlet • Common Servlet Sample • Continuation timeout sample • Continuation resume() sample • Continuation complete() sample 32 / Jetty Continuation

4. Servlet 3.0 33 / Jetty Continuation

4.1 Servlet 3.0 • Final release of Servlet 3.0 was announced at 10 Dec, 2009. • JSR(Java Specification Request) – 315 http://jcp.org/en/jsr/detail?id=315 • Glassfish 3 is based on Servlet 3.0 34 / Jetty Continuation

4.2 Servlet 3.0 new features • Asynchronous Servlets and comet support. • Web framework pluggability. • Use Annotations to define web.xml setting easier • @WebServlet, @WebFilter, @WebInitParam, @WebListner, @MultipartConfig • Modularization of web.xml • Use web-fragment.xml file http://www.jsptube.com/servlet-tutorials/servlet3/new-features.html 35 / Jetty Continuation

4.3 AsyncContext • AsyncContext interface • Package : javax.servlet • Class representing the execution context for an asynchronous operation that was initiated on a ServletRequest. • Methods : • setTimeout(long) • addListener(AsyncListener) • complete() … 36 / Jetty Continuation

4.4 ServletRequest • ServletRequest interface • Package : javax.servlet • Added Methods : • startAsync() • startAsync(ServletRequest , ServletResponse ) … 37 / Jetty Continuation

5. Conclusion 38 / Jetty Continuation

Jetty Continuation One Multi 39 / Jetty Continuation

Thank you.

Jetty Continuation - 이상민

by JavaCommunity.Org on Jul 13, 2010

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Jetty Continuation - 이상민 Presentation Transcript