The CNPG metrics exporter could not CONNECT to the `nextcloud` application
database, so every user-defined collector query against that target failed on
all three instances:
FATAL: permission denied for database "nextcloud" (SQLSTATE 42501)
DETAIL: User does not have CONNECT privilege.
The whole cnpg_pg_stat_* / pg_settings / pg_postmaster family was therefore
MISSING for nextcloud-db while the scrape target still reported up=1 — the blind
spot platform/cnpg/alerts.yaml's CNPGMetricsCollectorErroring was written to
catch. It had been firing on all three pods; measured before this change,
cnpg_pg_settings_setting had 765 series for keycloak, 765 for semaphore-db and
ZERO for nextcloud-db. Nextcloud's database had never been monitored.
Root cause is the live ACL, not the spec — all three Cluster specs bootstrap
identically:
nextcloud : datacl = {nextcloud=CTc/nextcloud} <- explicit, no PUBLIC entry
keycloak : datacl = NULL
semaphore : datacl = NULL
A NULL datacl means PostgreSQL's defaults, which include CONNECT for PUBLIC, so
keycloak and semaphore admit the exporter only by inheriting PUBLIC's implicit
CONNECT. On `nextcloud` something ran the equivalent of REVOKE ALL ON DATABASE
nextcloud FROM PUBLIC, which materialises datacl and drops that implicit entry.
That REVOKE is in neither this repo nor DECISIONS-LOG.md — it was applied out of
band, which is why the remedy has to be declarative rather than another hand-run
psql.
CNPG 1.30.0 cannot express a database-level GRANT (verified against the live
CRDs): `Database` has no ACL field (`allowConnections` is the datallowconn flag,
not a per-role grant), and managed.roles/DatabaseRole cover role attributes plus
`inRoles` membership only — and membership would hand the exporter the owner's
CREATE/TEMP and all table access to buy one CONNECT. postInitApplicationSQL runs
once at bootstrap, so it cannot repair the already-bootstrapped instances that
are actually broken. So this follows the pattern the repo already uses for state
Flux cannot reach: the level-triggered CronJob reconciler alongside
platform/keycloak/client-secret-reconciler.yaml. A one-shot Job is deliberately
avoided — a completed Job never re-runs, so a rebuild or PITR restore would
silently reopen the blind spot.
Exactly one privilege, and nothing else:
GRANT CONNECT ON DATABASE nextcloud TO cnpg_metrics_exporter;
giving `cnpg_metrics_exporter=c/nextcloud` — CONNECT only, no CREATE, no
TEMPORARY, no ownership, no superuser, no table or schema grants. Nothing more is
needed because CNPG already creates the role as a member of the built-in
pg_monitor role (verified on all three clusters), which carries the read access
the collector's pg_catalog queries want. It runs as the database OWNER, not a
superuser: enableSuperuserAccess stays off, and a database owner holds the grant
option on its own database.
Verified live on prod:
* the grant issued under SET ROLE nextcloud, proving no superuser is needed;
* permission-denied and "Error collecting user query" both went to 0 on
nextcloud-db-1/-2/-3, i.e. every collector query now succeeds;
* cnpg_pg_settings_setting now 765 series for nextcloud-db, matching the other
two, and cnpg_pg_postmaster_start_time present on all three instances;
* cnpg_last_error = 0 on all NINE instances, so keycloak-db and semaphore-db
are unaffected and their datacl is still NULL;
* convergence proven by revoking the grant again and letting the committed
CronJob restore it, then re-running it against a converged database to show
idempotence;
* CNPGMetricsCollectorErroring, firing on all three pods beforehand, has
cleared (`for: 6h` delays firing, not resolution).
Co-Authored-By: Claude Opus 5 <[email protected]>
jakman85andClaude Opus 5
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