The following revision refers to this bug:
  https://chromium.googlesource.com/external/github.com/luci/luci-py.git/+/6bdac1c6b9a57cdcd73d6b29ceba13a9547e2a40

commit 6bdac1c6b9a57cdcd73d6b29ceba13a9547e2a40
Author: maruel <maruel@chromium.org>
Date: Mon Jun 05 18:06:02 2017

Expose named caches as dimensions.

The implementation has a lot to be desired but the assumptions are well
documented and the implementation is trivial. Refactor later if needed.

Include smoke test to confirm that it works as expected.

R=nodir@chromium.org
BUG= 728127 

Review-Url: https://codereview.chromium.org/2911193003

[modify] https://crrev.com/6bdac1c6b9a57cdcd73d6b29ceba13a9547e2a40/appengine/swarming/local_smoke_test.py
[modify] https://crrev.com/6bdac1c6b9a57cdcd73d6b29ceba13a9547e2a40/appengine/swarming/swarming_bot/api/os_utilities.py
[modify] https://crrev.com/6bdac1c6b9a57cdcd73d6b29ceba13a9547e2a40/appengine/swarming/tools/start_bot.py

Sweet!

But I don't follow. Exactly what are the changes to the swarming request needed to take advantage of this?

Don, you can do something like "caches:foo" as a dimension to request a hot cache.

And if there is no hot cache, the request just picks any builder and runs?

PS: I'm really liking this approach.

Thanks a lot for this new dimension! Findit will also benefit a lot from this.

@robertocn, we could start the change on Findit side now.

Don, this is merely a foundation block for client-side decision. Swarming doesn't provide soft-dimensions at the moment, as discussed before.