[concurrency-interest] We need to add blocking methods to CompletionStage!

[Alex Otenko]

> On 25 Sep 2016, at 22:49, Martin Buchholz <martinrb at google.com> wrote:
> ...Say you are implementing some existing function with a traditional synchronous API.  Your implementation is multi-threaded, but that's an implementation detail.  Before you return to the caller, you must wait for the various parts of your computation to complete (the "join" part of fork/join).  It seems reasonable to wait forever.  If some part of your computation is interacting with an unreliable external resource, then it makes sense for that particular "wait" (which need not occupy a thread) to have a timeout.  Test methods, main methods and unix process reapers are all examples where it's reasonable to block forever.

More than that, cancelling the wait does not cancel the computation it was waiting for.

You need to time out / cancel the wait at the junctions where you have the power to arbitrate fair use of resource locked up in the caller, by the caller.

Alex