## Summary
- Fix invalid PromQL expression in `CNPGClusterOffline` alert rule that
causes vmalert pods to crash
- Fix PromQL logic so the alert fires correctly when cluster is offline
## Problem
The `CNPGClusterOffline` alert in
`packages/system/postgres-operator/alerts/cnpg-default-alerts.yaml` had
two issues:
1. **Syntax error** - Extra closing parenthesis causing vmalert pods to
crash:
```promql
sum by (namespace, pod) (cnpg_collector_up)) OR on() vector(0) == 0
^^-- extra )
```
2. **Logic error** - After removing the extra parenthesis, the
expression still had incorrect logic:
```promql
sum by (namespace, pod) (cnpg_collector_up) OR on() vector(0) == 0
```
This evaluates as `cnpg_collector_up OR (vector(0) == 0)` which fires
when the cluster is **online** (wrong behavior).
## Solution
Fix both issues by properly wrapping the OR expression in parentheses:
```promql
(sum by (namespace, pod) (cnpg_collector_up) OR on() vector(0)) == 0
```
This correctly fires when `cnpg_collector_up` is 0 or absent (cluster
actually offline).
## Test plan
- [ ] Verify vmalert pods start successfully after applying the fix
- [ ] Verify the alert rule is properly loaded
- [ ] Verify alert only fires when CNPG cluster is actually offline
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Andrei Kvapil
712c01419e