Make Swarming bot keep 5%+250MB of the disk free.

Make Swarming bot keep 5%+250MB of the disk free.

Also add more comments for disk self-quarantine thresholds definition, since
they are somewhat confusing.

This introduces a new knob, instead of tweaking self-quarantine knob, because:
  1) We don't want to brick all bots that happen to have <5% && >4GB of free
     disk space.
  2) We want to have some breathing room between desired free disk space and
     the disk space that triggers the quarantine.

BUG=678404
R=dsansome@chromium.org

Review-Url: https://codereview.chromium.org/2614623004
Committed: https://github.com/luci/luci-py/commit/e7fcbce2f8fcb01c3785d42278a913a33eb16356

[Vadim Sh., 2017-01-05 01:32:05]

The CQ bit was checked by vadimsh@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2017-01-05 01:32:07]

Dry run: 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, 2017-01-05 01:36:24]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2017-01-05 01:36:25]

Dry run: This issue passed the CQ dry run.

[dsansome, 2017-01-05 01:46:07]

lgtm

[Vadim Sh., 2017-01-05 01:46:52]

The CQ bit was checked by vadimsh@chromium.org

[commit-bot: I haz the power, 2017-01-05 01:47:03]

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, 2017-01-05 01:51:18]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1483580812019910, "parent_rev":
"ae56b3a60ca775afa9e049fa32470a15ef2e1c13", "commit_rev":
"e7fcbce2f8fcb01c3785d42278a913a33eb16356"}

[commit-bot: I haz the power, 2017-01-05 01:51:21]

Description was changed from

==========
Make Swarming bot keep 5%+250MB of the disk free.

Also add more comments for disk self-quarantine thresholds definition, since
they are somewhat confusing.

This introduces a new knob, instead of tweaking self-quarantine knob, because:
  1) We don't want to brick all bots that happen to have <5% && >4GB of free
     disk space.
  2) We want to have some breathing room between desired free disk space and
     the disk space that triggers the quarantine.

BUG=678404
R=dsansome@chromium.org
==========

to

==========
Make Swarming bot keep 5%+250MB of the disk free.

Also add more comments for disk self-quarantine thresholds definition, since
they are somewhat confusing.

This introduces a new knob, instead of tweaking self-quarantine knob, because:
  1) We don't want to brick all bots that happen to have <5% && >4GB of free
     disk space.
  2) We want to have some breathing room between desired free disk space and
     the disk space that triggers the quarantine.

BUG=678404
R=dsansome@chromium.org

Review-Url: https://codereview.chromium.org/2614623004
Committed:
https://github.com/luci/luci-py/commit/e7fcbce2f8fcb01c3785d42278a913a33eb16356
==========

[commit-bot: I haz the power, 2017-01-05 01:51:22]

Committed patchset #1 (id:1) as
https://github.com/luci/luci-py/commit/e7fcbce2f8fcb01c3785d42278a913a33eb16356