取消Google App Engine端点请求

Question

Im currently using GAE from Android. I have a search operation which performs what might be a long running query on the datastore (called from AsyncTask). The user has an option to logout from the app while this process is still running. Without an option to cancel this request the actual logout has to wait until the process finishes and the control is back to the client (which, as i said, can take a few seconds).

Is there a way to cancel a call to a GAE endpoint while the server is running and return the control to the client ? Thanks.

ps
Obviously, cancelling the AsyncTask only is not enough.

Answer 1

Personally, I put the server comm in a service so that requests can (usually) finish regardless of what the user does. In your case, could you let the user log out, but also let the request complete?

Otherwise, I don't know how to cleanly interrupt an endpoint request. Unfortunately, the actual blocking operation is buried in the endpoints (Google API Client library) code and no cancel operation is exposed that I'm aware of.

When you write that cancelling the task - AsyncTask.cancel(boolean mayInterruptIfRunning) - is not enough, is that because you've tried it and it doesn't interrupt a blocked operation.

Answer 2

No, Google Endpoints use servlets and servlets have no (standard) way of telling a running request to cancel it's work. You will need to build something proprietary.

For example: in your long-running process on server you in it's main loop check if user is still logged in (via a flag in the datastore or memcache). If this flag tells you that user is logged out, then you cancel the processing and return. Also a login/logout procedure must appropriately set this flag.