## Context
Wave 7 of the state-drift consolidation plan. The drift-detection pipeline
(`.woodpecker/drift-detection.yml`) already ran terragrunt plan on every
stack daily and Slack-posted a summary, but its output was ephemeral —
nothing persisted in Prometheus, so there was no historical view of which
stacks drift, when, or for how long. Following the convergence work in
waves 1–6 (168 KYVERNO_LIFECYCLE_V1 markers, 4 stacks adopted, Phase 4
mysql cleanup), the baseline is clean enough that *new* drift should
stand out. That only works if we have observability.
## This change
### `.woodpecker/drift-detection.yml`
Enhances the existing cron pipeline to push a batched set of metrics to
the in-cluster Pushgateway (`prometheus-prometheus-pushgateway.monitoring:9091`)
after each run:
| Metric | Kind | Purpose |
|---|---|---|
| `drift_stack_state{stack}` | gauge, 0/1/2 | 0=clean, 1=drift, 2=error |
| `drift_stack_first_seen{stack}` | gauge (unix seconds) | Preserved across runs for drift-age tracking |
| `drift_stack_age_hours{stack}` | gauge (hours) | Computed from `first_seen` |
| `drift_stack_count` | gauge (count) | Total drifted stacks this run |
| `drift_error_count` | gauge (count) | Total plan-errored stacks |
| `drift_clean_count` | gauge (count) | Total clean stacks |
| `drift_detection_last_run_timestamp` | gauge (unix seconds) | Pipeline heartbeat |
First-seen preservation: on each drift hit, the pipeline queries
Pushgateway for the existing `drift_stack_first_seen{stack=<stack>}`
value. If present and non-zero, reuse it; otherwise stamp with `NOW`.
That means age-hours grows monotonically until the stack goes clean
(at which point state=0 resets first_seen by omission).
Atomic batched push: all metrics for a run are POST'd in a single
HTTP request. Pushgateway doesn't support atomic multi-metric updates
natively, but batching at the pipeline layer prevents half-updated
state if the curl is interrupted mid-run (the second call would just
fail the entire run and alert on `DriftDetectionStale`).
### `stacks/monitoring/.../prometheus_chart_values.tpl`
New `Infrastructure Drift` alert group with three rules:
- **DriftDetectionStale** (warning, 30m): fires if
`drift_detection_last_run_timestamp` is older than 26h. Gives a 2h
grace window on top of the 24h cron so transient Pushgateway or
cluster unavailability doesn't false-alarm. Guards against the
pipeline silently failing or the cron not firing.
- **DriftUnaddressed** (warning, 1h): fires if any stack has
`drift_stack_age_hours > 72` — three days of unacknowledged drift.
Three days is long enough to absorb weekends + typical review cycles
but short enough to force follow-up before drift compounds.
- **DriftStacksMany** (warning, 30m): fires if `drift_stack_count > 10`
in a single run. Sudden wide drift usually signals systemic causes
(new admission webhook, provider version bump, cluster-wide CRD
upgrade) rather than individual configuration errors, and the alert
body nudges toward that diagnosis.
Applied to `stacks/monitoring` this session — 1 helm_release changed,
no other drift surfaced.
## What is NOT in this change
- The Wave 7 **GitHub issue auto-filer** — the full plan included
filing a `drift-detected` issue per drifted stack. Deferred because
it requires wiring the `file-issue` skill's convention + a gh token
exposed to Woodpecker, both of which need separate setup. The Slack
alert covers the same need at lower fidelity in the meantime.
- The Wave 7 **PG drift_history table** — would provide the richest
historical view but adds a new DB schema dependency for a CI
pipeline. Pushgateway + Prometheus handle the 72h window we care
about; PG history is nice-to-have for quarterly reviews.
- Auto-apply marker (`# DRIFT_AUTO_APPLY_OK`) — premature until the
baseline has been stable for a few cycles.
Follow-ups tracked: file dedicated beads items for GH-issue filer + PG
drift_history.
## Verification
```
$ cd stacks/monitoring && ../../scripts/tg apply --non-interactive
Apply complete! Resources: 0 added, 1 changed, 0 destroyed.
# After next cron run (cron expr: "drift-detection" in Woodpecker UI):
$ curl -s http://prometheus-prometheus-pushgateway.monitoring:9091/metrics \
| grep -c '^drift_'
# expect a positive number
```
## Reproduce locally
1. `git pull`
2. Check Prometheus rules: `curl -sk https://prometheus.viktorbarzin.lan/api/v1/rules | jq '.data.groups[] | select(.name == "Infrastructure Drift")'`
3. Manually trigger the Woodpecker cron and watch Pushgateway populate.
Refs: Wave 7 umbrella (code-hl1)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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