this is the big picture:

a. frontend application with Undertow

b. backend application with Undertow and Resteasy for REST API

A serves JS,HTML,CSS and exposes B's REST API with a proxy servlet (https://github.com/mitre/HTTP-Proxy-Servlet).

Since one method of my backend API does some image processing, I'm wondering how to implement this method in an asynchronous way.

On B side I'm reading Resteasy documentation http://docs.jboss.org/resteasy/docs/3.0.9.Final/userguide/html_single/#Asynchronous_HTTP_Request_Processing

On A side is there something could help me from undertow to proxy in async way the requests to this method of B?