Update floating builder logic, add to "chromiumos"

Update floating builder logic, add to "chromiumos"

The floating builder logic had several flaws, notably:
- It was broken: adding more than one (see crbug.com/600479).
- It was too complex. It was written generically with the idea that other
  waterfalls may want to use it (hah!)

This updates the logic to clearly have a primary and floating slave set
rather than a generic "strata" concept, and to specifically prefer them in a
predefined order. This also implements floating builders for PFQs (in builder
config), ups the number of floating builders from 1 to 2 for paladins, and
enrolls the floating builder logic for the "chromiumos" waterfall paladins.

BUG=chromium:637166
TEST=local

Committed: https://chromium.googlesource.com/chromium/tools/build/+/525b79ec0f5e47f3d203094c2bd7f1a797736ea2

[dnj, 2016-08-15 19:17:25]

dnj@chromium.org changed reviewers:
+ bpastene@chromium.org

[dnj, 2016-08-15 19:17:26]

PTAL

[bpastene, 2016-08-15 20:06:29]

lgtm! thanks for the walkthrough, that's one heck of a scheduler :)

[dnj, 2016-08-15 23:32:26]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-08-15 23:32:37]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dnj, 2016-08-15 23:37:16]

The CQ bit was checked by dnj@chromium.org

[dnj, 2016-08-15 23:37:16]

The patchset sent to the CQ was uploaded after l-g-t-m from
bpastene@chromium.org
Link to the patchset: https://codereview.chromium.org/2250443002/#ps20001
(title: "Fix variable nam.")

[commit-bot: I haz the power, 2016-08-15 23:37:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dnj, 2016-08-15 23:44:23]

The CQ bit was checked by dnj@chromium.org

[dnj, 2016-08-15 23:44:24]

The patchset sent to the CQ was uploaded after l-g-t-m from
bpastene@chromium.org
Link to the patchset: https://codereview.chromium.org/2250443002/#ps40001
(title: "Pylint fixes.")

[commit-bot: I haz the power, 2016-08-15 23:44:27]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-15 23:48:26]

Description was changed from

==========
Update floating builder logic, add to "chromiumos"

The floating builder logic had several flaws, notably:
- It was broken: adding more than one (see crbug.com/600479).
- It was too complex. It was written generically with the idea that other
  waterfalls may want to use it (hah!)

This updates the logic to clearly have a primary and floating slave set
rather than a generic "strata" concept, and to specifically prefer them in a
predefined order. This also implements floating builders for PFQs (in builder
config), ups the number of floating builders from 1 to 2 for paladins, and
enrolls the floating builder logic for the "chromiumos" waterfall paladins.

BUG=chromium:637166
TEST=local
==========

to

==========
Update floating builder logic, add to "chromiumos"

The floating builder logic had several flaws, notably:
- It was broken: adding more than one (see crbug.com/600479).
- It was too complex. It was written generically with the idea that other
  waterfalls may want to use it (hah!)

This updates the logic to clearly have a primary and floating slave set
rather than a generic "strata" concept, and to specifically prefer them in a
predefined order. This also implements floating builders for PFQs (in builder
config), ups the number of floating builders from 1 to 2 for paladins, and
enrolls the floating builder logic for the "chromiumos" waterfall paladins.

BUG=chromium:637166
TEST=local

Committed:
https://chromium.googlesource.com/chromium/tools/build/+/525b79ec0f5e47f3d203...
==========

[commit-bot: I haz the power, 2016-08-15 23:48:27]

Committed patchset #3 (id:40001) as
https://chromium.googlesource.com/chromium/tools/build/+/525b79ec0f5e47f3d203...