aumentando a eficiência do web container usando chamadas assíncronas

Globalcode – Open4education

Trilha – Java

Rafael Torres Coelho Soares (Tuelho)[email protected]

@rafaeltuelho

Aumentando a eficiência do Web Container usando chamadas Assíncronas


Agenda

Web 2.0

Web Assíncrona

Servlet 3.0 (JSR 315)

Demo


Tuelho

Trabalho com Java desde 2004Desenvolvimento (back-end)

Infraestrutura Java

JBoss.orgrhq-project (contributor)

Red Hat (2010-2012)Serviços e consultoria

Oracle Fusion MiddlewareWeblogic Application Server (consultoria)


Web interativa


Web 2.0 (mais interativa e dinâmica)


Novas tecnologias


Novos modelos de comunicação

Server events

Client asynchronous requests

pooling

push


Server busy!


Comunicação HTTP

thread per connectionBaseado no http 1.1 (persistent connection)

thread per request modelnon-blocking I/O (NIO) – Java 1.4


WebServer

Http Thread Pool

T#1

T#2

T#6

T#3

T#5T#

4

thread-per-connection

idle

Http Connection

T#5

response

request active

Keep alive timeout… ouConnection timeout

c1c1 c1

Connection Queue(backlog)

C#C1#


c1c1 c1

thread-per-request

WebServer

Http Thread Pool

T#1

T#2

T#6

T#3

T#5T#

4 idle

T#5Response #1

Request #1 active

request #2

T#1Response #2

Response time…

Connection Queue(backlog)

C#C1#


Web Assíncrona: problemas e motivações

Long Running Requests

Real time updates


Servlet 3.0: melhorias

JSR 315 (2009)Asynchronous support

Ease of configuration

Annotations

Pluggability/Modularization: web fragments

Enhancements to existing APIs


Async Context

Javax.servlet.AsyncContext.start()

“Causes the container to dispatch a thread, possibly from a managed thread pool, to run the specified Runnable.”

e daí? O que faço com isso?


Ciclo de uma requsição assíncrona

① Cliente envia uma requisição

② Servidor invoca um Servlet (nova thread alocada)

③ O Servlet invoca request.startAsync(), salva AsyncContext, e

retorna

④ A thread alocada é liberada, mas o response permanece aberto

⑤ Outra thread (pool separado) utiliza o AsyncContext para concluir a

resposta (asyncContext.complete() ou

asyncContext.dispatch())

⑥ Cliente recebe a resposta do servidor.


Processamento assíncrono

WebServer

Http Thread Pool

T#5T#2

T#6

T#3

T#4 idle

T#5

Response

Request active Servlet Context

Managed Thread Pool

request.startAsync()

asyncContext.complete()

1

3

2

5

6

4


Sample code

@WebServlet(name = "MyAsyncServlet", urlPatterns = {"/MyAsyncServlet"}, asyncSupported = true)public class MyAsyncServlet extends HttpServlet {

public void doGet(...) { final AsyncContext asyncContext = request.startAsync();

asyncContext.start(new Runnable() { @ Override public void run() { // do some work here which involves waiting ... asyncContext.complete(); } });}


JavaSE 5 Executor Framework


JavaSE 5 Executor Framework: conceitos

Task

Runnable

Callable

Thread

Synchronous processing

Asynchronous processing

Thread pool

ExecutorService

ThreadPoolExecutor

SchedulePoolExecutor


ThreadPoolExecutor

Thread pool

Work queue

Bounded

Unbounded

Handler (saturation policy)

Defaults: RejectedExecutionException runtime exception

Thread Factory


Executor: main steps

① Criar uma instância de Executor

② Criar uma taskRunnable ou Callable

③ Submeter a task para execução

④ Executar a task

⑤ Finalizar o Executor


ServletContextListener@WebListenerpublic class ServletContextListener implements javax.servlet.ServletContextListener { @Override public void contextInitialized(ServletContextEvent sce) { Executor executor = new ThreadPoolExecutor(10, 100, 60000L, TimeUnit.MILLISECONDS, new LinkedBlockingQueue<Runnable>(100)); sce.getServletContext(). setAttribute("threadPoolExecutor", executor); }

@Override public void contextDestroyed(ServletContextEvent sce) { ThreadPoolExecutor executor = (ThreadPoolExecutor)sce.getServletContext() .getAttribute("threadPoolExecutor"); executor.shutdownNow(); }}


MyAsyncServlet

protected void processRequest(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

try { AsyncContext asyncCtx = request.startAsync(); ThreadPoolExecutor executor = (ThreadPoolExecutor) request.getServletContext(). getAttribute("threadPoolExecutor"); asyncCtx.setTimeout(-1L); asyncCtx.addListener(new ServletAsyncListener());

//delegate long running process to an "async" thread executor.execute(new AsyncTask(asyncCtx)); } finally { }}


AsyncTask (Runnable instance)public class AsyncTask implements Runnable { private AsyncContext asyncContext;

public AsyncTask(AsyncContext asyncContext) { this.asyncContext = asyncContext; }

@Override public void run() { // acesso remoto, query, processamento pesado // escreve na resposta… asyncContext.complete(); // ou asyncContext.dispatch(); }}


Demo: sync vs. async

Requisição Servlet Rest Service

Rest


… mas eu não uso servlet

JEE 6EJB @Asynchronous

CDI Events

JSF Component FrameworkPrimefaces/RichFaces

ServerPush com Atmosphere

Ajax Pooling

JEE 7Java Websocket Spec (JSR 356)


Web Assíncrona: implementações

CometTraditional pooling

Long pooling

Http Streaming

WebSocket protocol

Algumas implementações alternativasAtmosphere Framework (github.com/Atmosphere/)

Tomcat: CometProcessor class

Jetty 6: Continuations

Grizzly (glassfish): CometEngine class.


DÚVIDAS?


Contatos

[email protected]

@rafaeltuelho

http://rafaeltuelho.net.br

aumentando a eficiência do web container usando chamadas assíncronas

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