investigate async http client integration about feign HOT 13 OPEN

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cc @benjchristensen

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That makes sense, with IncrementalCallback we can support both blocking and non-blocking IO.

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Is there a reason to keep the synchronous method?

// existing
  Response execute(Request request, Options options) throws IOException;

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yes because most api interactions with http are still synchronous and we
don't want to or need to eliminate "easy mode" just to facilitate advanced.

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for example, implementing Client with url connection (a synchronous client) could reuse a base implementation of forking off the request. I've in the past made the mistake of forcing synchronous http calls through blocking futures (jclouds), and don't want to repeat that as a default, particularly as it would require sync calls to unnecessarily fire threads.

Having an interface that supports both means allows folks to decide at configuration time how they prefer to interact, whether that's making everything block on futures, use real async tasks or use async only when asked.

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Any update on this? Are you still planning to integrate this in a future release?
Thanks.

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Please implement support for async, it's a pretty big drawback right now when your client and MVC controller can't share the same contract because of the use of (for example) DeferredResult.

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DeferredResult is a spring MVC type, right? If that's the goal, maybe
raise an issue in spring-cloud-netflix where the MVC contract lives?

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@adriancole Yes, it is a spring MVC type, however, if the underlying implementation doesn't support async I don't see how spring-cloud-netflix would be able to solve the problem. I will take your suggestion and raise an issue there, though, in the hopes that maybe there is a workaround. Thanks for the quick response!

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+1. It's quite strange that popular general purpose HTTP client doesn't support async.

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I see. Actually planning to use Hystrix w/ Rx. However what concerns me is the lack of non-blocking client support. Maybe I'm missing something, but it seems that Feign uses either Apache HttpClient or OkHttp - both in blocking mode? Was hoping that Async HttpClient would allow me to do non-blocking requests.

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