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Posted to commits@cloudstack.apache.org by "nagaboinaramgopal (via GitHub)" <gi...@apache.org> on 2026/10/08 18:47:52 UTC
[PR] cluster DRS: power off under-utilized hosts and wake them on demand [cloudstack]
nagaboinaramgopal opened a new pull request, #14371:
URL: https://github.com/apache/cloudstack/pull/14371
### Description
Extends the existing cluster DRS service with optional host power management. When a cluster
drops below a configurable low utilization threshold, DRS disables an empty, out-of-band
manageable host, records a durable host detail marking that DRS powered it off, and issues the
out-of-band power-off. When the cluster rises above a high threshold, DRS powers a host it turned
off earlier back on. At most one host is powered off or on per poll, and the remaining hosts must
be able to carry the load before a host is released.
A host is only powered off once it is genuinely empty. If no host is empty, an optional active
evacuation mode drains the least-loaded releasable host (migrating its VMs to the others within
the DRS migration budget) so a later poll can power it off once empty. Draining is disabled first
so the allocator stops targeting it, and a drain that stops making progress (its migrations keep
being rejected for affinity, host tags or storage) is abandoned and the host returned to service
rather than being re-submitted forever. An optional predictive mode folds a short least-squares
forecast of recent utilization into the decision, so a rising trend wakes a host sooner and a
transient dip does not trigger a power-off.
The power-off path is ordered so the durable marker is written before the irreversible power
operation: a management-server crash in between leaves a host DRS still recognises and powers back
on, never one stranded off. A host that comes back by any path is reconciled (re-enabled, unmarked)
on the next poll, and a power-off whose command reports failure is left disabled and marked for
reconciliation rather than assumed still running.
Everything is off by default behind per-cluster settings: drs.power.management.enable,
drs.power.management.low.threshold, drs.power.management.high.threshold,
drs.power.management.evacuate.enable, drs.predictive.enable and drs.predictive.window. It requires
automatic DRS and out-of-band management to be configured on the cluster. No schema change: it uses
a host detail and config keys.
### Types of changes
- [ ] Breaking change (fix or feature that would cause existing functionality to change)
- [x] New feature (non-breaking change which adds functionality)
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] Enhancement (improves an existing feature and functionality)
- [ ] Cleanup (Code refactoring and cleanup, that may add test cases)
- [ ] Build/CI
- [ ] Test (unit or integration test code)
### Feature/Enhancement Scale or Bug Severity
#### Feature/Enhancement Scale
- [x] Major
- [ ] Minor
### How Has This Been Tested?
Unit tests cover the decision and lifecycle logic: the release and wake thresholds, the predictive
forecast, the first-fit placement pre-check, the power-off ordering (marker before the power
operation, disable gated on the state transition, no rollback on an unconfirmed failure), the
power-on marker handling, the in-flight-plan guard, and the drain lifecycle (wait while a batch is
migrating, abandon on no progress or when VMs no longer fit, disable the candidate, power the
emptied host off only while it is still manageable and releasable). 38 tests pass across
ClusterDrsPowerManagementTest and ClusterDrsPowerOrchestrationTest.
#### How did you try to break this feature and the system with this change?
The logic was audited for the failure paths that matter for powering real hardware off: a
management-server crash in the window between disabling, marking and powering off a host; a
power-off command that reports failure after the host already went down; an accepted but
unconfirmed power-on; a host returning by a path other than a DRS wake; the allocator placing new
VMs on a host mid-drain; a drain whose VMs cannot actually be migrated; and a host going down or
being disabled by an operator mid-drain. Power management is skipped entirely for a cluster that
has a DRS migration plan in flight so a migration source or destination is never powered off under
it. The sub-minute allocation race between powering a host off and its agent disconnecting is
handled by disabling the host first and detaching its agent without investigation.
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Re: [PR] cluster DRS: power off under-utilized hosts and wake them on demand [cloudstack]
Posted by "codecov[bot] (via GitHub)" <gi...@apache.org>.
codecov[bot] commented on PR #14371:
URL: https://github.com/apache/cloudstack/pull/14371#issuecomment-6338799983
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:white_check_mark: All modified and coverable lines are covered by tests.
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<details><summary>Additional details and impacted files</summary>
```diff
@@ Coverage Diff @@
## main #14371 +/- ##
=============================================
- Coverage 20.21% 3.69% -16.53%
=============================================
Files 6426 491 -5935
Lines 580181 42220 -537961
Branches 71033 7974 -63059
=============================================
- Hits 117282 1558 -115724
+ Misses 450184 40436 -409748
+ Partials 12715 226 -12489
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