Java Async REST web service using Jersey?
Alan,the right thing to do is to use HTTP's 202 Accepted return code and include in the response body a link that points to a page the client can poll to check the status of the request.
In a machine2machine context you will need to design your media type (or microformat etc.) for those responses so a machine client can 'understand' them.
See http://www.w3.org/Protocols/rfc2616/rfc2616-sec10.html#sec10.2.3
Maybe also look at the almost standardized new HTTP Link header for that purpose.
https://datatracker.ietf.org/doc/html/draft-nottingham-http-link-header-03
Jan