Cluster grew past the 100-conn default — steady-state idle was 90/100,
leaving zero headroom for terragrunt applies or transient surges. The
ceiling was being discovered by Terraform crashing (pq: "remaining
connection slots are reserved for roles with the SUPERUSER attribute"),
not by alerting, because we had no PG scrape config at all.
dbaas (Tier 0):
* max_connections: 100 → 200
* shared_buffers: 512MB → 1GB (Postgres recommends ~25% of pod memory)
* effective_cache_size: 1536MB → 2560MB (scaled with pod memory)
* pod memory: 2Gi → 3Gi (rough rule of thumb: enough for shared_buffers
+ ~16MB work_mem * concurrent sorts + OS cache + overhead)
* Triggers bump on null_resource.pg_cluster forces CNPG to re-apply,
which rolls the cluster (standby first, then primary failover).
monitoring:
* New scrape job 'cnpg' on dbaas namespace pods labeled
cnpg.io/podRole=instance, port name=metrics (9187). Relabels add
cnpg_cluster + cnpg_role labels for alert grouping.
* PGConnectionsHigh (warning, >85% for 10m) — heads-up before exhaustion.
* PGConnectionsCritical (critical, >95% for 3m) — last call before
refusing connections.
Verified: cnpg targets up, sum(cnpg_backends_total)=84, max_connections
metric=200, alert ratio 0.42 → both alerts inactive.
20774f794d