con 2107- think async: embrace and get addicted to the asynchronicity of ee

Copyright © 2014, Oracle and/or its affiliates. All rights reserved. |

Think Async

Masoud Kalali, SoEware Engineer, ORACLE, @MasoudKalal

Embrace and Get Addicted to the Asynchronicity of EE


Safe Harbor Statement The following is intended to outline our general product direcNon. It is intended for informaNon purposes only, and may not be incorporated into any contract. It is not a commitment to deliver any material, code, or funcNonality, and should not be relied upon in making purchasing decisions. The development, release, and Nming of any features or funcNonality described for Oracle’s products remains at the sole discreNon of Oracle.


Program Agenda

IntroducNon

Why to think Async

A simple case of using Async

JMS (2.0)

Async Servlet

Async JAX-‐RS

Async EJBs

1

2

3

4

5

6

7


Speakers

Masoud Kalali •  SoEware engineer, author, blogger •  Long advocate of GlassFish and Java EE •  Tweets at @MasoudKalali


Why to think Async? •  To be]er model what we develop for •  To further decouple – Ease of administraNon – Ease of tuning – Ease of maintenance

•  Improve consumers experience – An API consumer – A direct GUI for human use – etc.


Java EE And ASynchronicity •  Long present JMS – To be used almost everywhere

•  Servlet 3.0/ 3.1 – Asynchronous Servlets – None blocking IO

•  JAX-‐RS 2.0 – Server side – Client side

•  Asynchronous Session Beans – Server side – Client side


A simple asynchronous nourished use case

Client

Cache

Query

Processor

JMS

Queue

JMS

Queue

Async Servlet

MDB

ID, AsyncContext

Query Requests in JMS

Chunks of Query results Consume result chunks and send it back via AsyncContext 1

1 2.1 3

2

4….

5…. 6…. 7….

8….

No HA/Fault tolerance considered, This Is a very basic block diagram to help with the presentaNon



• One JMS queue for sending the query requests • One JMS queue which will get chunks of query results • An MDB which will consume the query result messages – Uses the cache and the id in the message to pick up the right AsyncContext – As long as the message does not say it is done it will not conclude the response

• Complete the response when JMS message implies

More details of the Messaging components



• Asynchronous Servlet receiving the requests • Caching the AsynContext and a query Id •  Sending the Query message to the JMS queue – Including the query Id

•  Leave it to the MDB to update the response • Have a AsyncListener to send proper response if Nmeouts

More details of the Servlet components



• A browser • Can be – A SSE client – A COMET, Long Polling request

Some basics on the client side


JMS (2.0) A brief overview


JMS: A brief overview I • Broker • Message • Queue – Producers – Consumers

•  Topic – Publishers – Subscribers

• Accessible from inside or outside a Java EE


JMS 2.0: A brief overview: • MulNple Consumers Allowed on the Same Topic SubscripNon •  Delivery Delay •  Sending Messages Asynchronously – Send the message and get callback when it is acknowledged by broker

•  JMSXDeliveryCount message property No longer opNonal •  Standard MDB ConfiguraNon ProperNes as part of @MessageDriven – desNnaNonType –  subscripNonDurability – acknowledgeMode –  subscripNonName –  ...


Servlet 3.0 Asynchronous servlet


Servlet 3.0 Asynchronicity • Why we want it – More throughput – Be]er architecture mapping

• How it works – @WebServlet.asyncSupported, async-‐supported in XML config! – AsyncContext – AsyncListener


Servlet 3.0 Asynchronicity : AsyncContext • Adding listeners • Doing request dispatching • Accessing ServletRequest • Accessing ServletResponse • Concluding the request/response •  Semng, gemng Nmeouts


Servlet 3.0 Asynchronicity : AsyncListener • Get callback on important events on an async request processing • onComplete(AsyncEvent asyncEvent) • onError(AsyncEvent asyncEvent) • onStartAsync(AsyncEvent asyncEvent) • onTimeout(AsyncEvent asyncEvent)


Servlet 3.0 Asynchronicity : A li]le bit of code @WebServlet(asyncSupported = true, value = ”/query-‐servlet") public class QueryServlet extends H]pServlet { protected void doGet(H]pServletRequest request, H]pServletResponse response) throws ServletExcepNon, IOExcepNon { String id=...; cache.put(id,request.startAsync()); sendQueryMessage(id, request); } }


Servlet 3.1 Non-‐blocking IO


Servlet 3.1: Non-‐Blocking IO • Why do we want it? • How does it work? – ReadListener: To read inbound data when available – WriteListener: To write data when possible – Changes in ServletOutputStream •  isReady() •  setWriteListener(…)

– Changes in ServletInputStream •  isFinished() •  isReady() •  setReadListener(…)


Servlet 3.1: Non-‐Blocking IO: ReadListener •  To get callbacks on ServletInputStream events – onDataAvailable – OnAllDataRead – onError


Servlet 3.1: Non-‐Blocking IO: WriteListener •  To get noNfied on ServletOutputStream events – onError – onWritePossible


Asyncronicity in JAX-‐RS 2.0 • Why would we need it? • How does it work? – @Asynchronous – ExecuNonContext for programmaNc decision to do or not to do async – AsyncResponse – @Suspended – CompleNonCallback – ConnecNonCallbck


Asyncronicity in JAX-‐RS 2.0: Server-‐side I

• On the serverside: – @Asynchronous: Annotate a sub-‐resource as Asynchronous – AsyncResponse: Provides results an acNons on the running request •  semng Nmeout •  registering callbacks •  resume, cancel suspended request processing •  updaNng the response

– @Suspended: To inject a suspended AsyncResponse into a sub-‐resource parameter

How to mark a resource as Asynchronous


Asyncronicity in JAX-‐RS 2.0: Server-‐side simple code @Path("/api/query")

public class MyResource {

@Context private ExecuUonContext ctx;

@GET @Produce(“applicaUon/json”)

@Asynchronous

@Path(“api/matching-‐query”)

public void prepMatchingQueryResult(@Suspended AsyncResponse ar, @QueryParam String p1… ) {

executor.submit( new Runnable() {

public void run() {

JsonObject response = getQueryResult(p1…);

ctx.resume(response); //container thread picks up and conUnue

} });

ctx.suspend(); // Suspend connecUon and return

} … }

Server Code:


Asyncronicity in JAX-‐RS 2.0: client-‐side simple code

Future<JsonObject> future = client.

target(“/api/query/matching-‐query”).queryParam(...).request().async().get(JsonObject.class);

try {

JsonObject queryResult = future.get(30, TimeUnit.SECONDS);

} catch (TimeoutExcepNon ex) {

//

}

Client-‐Side with future


Asyncronicity in JAX-‐RS 2.0: client-‐side simple code Client-‐Side with callback Future<JsonObject> future = client. target(“/api/query/matching-‐query”).

queryParam(...).request().async().get(new InvocaNonCallback<JsonObject>() {

@Override public void completed(JsonObject response) {

//InvocaNon happens and some response is back (404, 200, etc.)

}

@Override public void failed(Throwable throwable) {

//InvocaNon fails (client side)

}

});


Asyncronicity in JAX-‐RS 2.0: Server-‐side II

•  Single method interface •  void onComplete(Throwable t) •  signal compleNon of serving a request

CompleUonCallback


Asyncronicity in JAX-‐RS 2.0: Server-‐side III

•  Single method interface •  void onDisconnect(AsyncResponse disconnected) •  signals interrupNon in client connecNon before compleNon

ConnecUonCallback


Asynchronous And long running jobs in REST

• MulN-‐step long running jobs not suitable with JAX-‐RS Async •  Send 202 where response is not ready with LocaNon header – Intelligent enough client can query the resource LocaUon with the given Retry-‐Ader header

Don’t keep unnecessary resources for where not needed!


EJB 3.1 Asynchronicity in Session Beans


Asynchronicity in EJB 3.1 • Works on session beans – fire and forget – Using Future<V> to decide on compleNon

• AsyncResult as container specific vehicle – Passes the result to Future<V>

• As simple as using @Asynchronous on method/bean • Method should return Future<V> • Client can poll the future for CompleNon


Asynchronicity in EJB 3.1: Simple code sample

@Stateless public class QueryProcessor { @Asynchronous public Future<QueryResult> processQuery(QueryCrit crit){ try{

QueryResult result= prepQueryResult(crit); return new AsyncResult(result);

}catch(ExcepNon e){ //handle

return new AsyncResult(FAILURE_RESULT); } }}

Server-‐side code


Asynchronicity in EJB 3.1: Simple code sample

@Inject QueryProcessor queryProcessor; private JsonObject prepareQueryResult(String... params){ QueryCrit crit = new QueryCrit(params) Future<QueryResult> result=queryProcessor.prepQueryResult(crit); //poll the Future.. There is no callback here... } }

cliet-‐side code


Java EE 7 and SSE Asynchronicity in SSE


Server-‐Sent Events §  HTML 5 component

§  Client subscribe to event source

§  UnidirecNonal channel between server and client

§  Events can be streamed from server to client when happens

§  ConnecNon stays open

§  event handling on client side §  onMessage

§  onError

§  etc.

§  SubscripNon resuming


Server-‐Sent Events § Can be developed using a plain Servlet

§  use the right media type

§  use the correct message format

§  Jersey provides support not JAX-‐RS yet §  Server side to turn a JAX-‐RS endpoint to SSE broadcaster

§  Client side to subscribe and consume SS events


Comments, QuesNons?


•  RESTful Services Patterns and best practices By Bhakti Mehta •  Bhakti’s blog: https://www.java.net/blog/bhaktimehta •  Book’s sample codes: •  CCL photos used in slides:

•  https://www.flickr.com/photos/treehouse1977/2892417805/ •  https://www.flickr.com/photos/treehouse1977/2892417805/ •  https://www.flickr.com/photos/essjay/165928100/ •  https://www.flickr.com/photos/jforth/4413370462/ •  https://www.flickr.com/photos/sakalak/8737872379/ •  https://www.flickr.com/photos/jbparrott/8980026600 •  https://www.flickr.com/photos/pentadact/36593493/ •  https://www.flickr.com/photos/jasohill/4442279347/ •  https://www.flickr.com/photos/mdsharpe/5075953655 •  https://www.flickr.com/photos/chuqvr/8329512894/

Resources

con 2107- think async: embrace and get addicted to the asynchronicity of ee

Technology

asynccontext asynclistener

speaker soewareengineer

dowe howdoesitwork