Pattern for designing a scalable web service

I am writing a web service in Java which needs to handle a large number of requests / second. The general flow will be:

• Web service receives a request from client
• Returns a 'keep polling me' response to client
• Calls another web service (or services), and waits for them to respond (with a timeout)
• Client po开发者_如何学Golls our web service, until it receives a response (with a timeout)

Researching on the Internet, I have found two general approaches to writing web services:

• Spawn a thread for each request
• Use the Reactor pattern (central dispatcher thread responds to IO events)

Do you have a recommendation for which approach is generally better, and what are the pros/cons of each approach? I would also appreciate pointers to examples.

Don't think multi-threading. Think asynchronously. I happened to have just coded an async handler that ran 2,000 RPS with <10 threads in IIS. Not sure how java works since I'm a .net guy but I gotta believe they have similar BeginXXX/EndXXX methods. If you ever spawn a thread then you're not considering all the places your code can block: data base IO, File I/O, web services, etc. These are the places your performance will cause your site to be slow.

Async, Async, Async.

Chant and repeat.

In addition to "No Refunds No Returns" response, I'd say yeah "Think Asynchronously" as you should be allowing your container to manage the multi-threading/scalability and high-availability issues of the web services it has deployed, this allows you to set-up things like clustering and so forth using your application container.

EDIT: So in conclusion, there isn't a pattern as such, maybe you should explore the scalability/availability features of your application container...

Asynchronism is indeed the right approach but don't manage this yourself, use something that supports asynchronous web service invocation like JAX-WS 2.0 (which uses the Future interface and/or the Executor framework from java.util.concurrent). See Asynchronous Web Service Invocation with JAX-WS 2.0.