Aleksei Sviridkin 6ab3e0be78 feat(postgres): allow preloading an allowlist of shipped modules (#3506)
## What this PR does

- Adds `postgresql.sharedPreloadLibraries`, a closed enum of four module
names that already ship in the CloudNativePG PostgreSQL image, rendered
onto the CNPG `Cluster` field of the same meaning.
- Leaves the `shared_preload_libraries` entry in the
`postgresql.parameters` blocklist exactly as it is.
- Adds `tests/shared_preload_libraries_test.yaml`: absent by default,
single and multiple libraries, no interference with `parameters`, schema
rejection of a non-allowlisted name and of an absolute path, and the
parameter blocklist still firing when the allowlist is in use.
- Adds `hack/check-postgres-preload-allowlist.bats`, which renders the
chart with `--skip-schema-validation` to exercise the template-side
allowlist that helm-unittest never reaches, and checks that it matches
the schema enum.

`shared_preload_libraries` is blocked in `postgresql.parameters`, and
rightly so: the parameter is free text and accepts a path, so it can
point at a writable location such as the PGDATA volume. The block does
not make every preloadable module unreachable, though. CloudNativePG
carries a managed extensions list (`ManagedExtensions` in
`pkg/postgres/configuration.go`, checked on v1.30.0, the operator
version in this repo): as soon as a parameter under the
`pg_stat_statements.`, `auto_explain.` or `pgaudit.` prefix is set, the
operator adds that library to `shared_preload_libraries` itself, and for
`pg_stat_statements` and `pgaudit` it also runs `CREATE EXTENSION`. The
chart already passes such keys through, so
`postgresql.parameters."pg_stat_statements.track": all` works on main
today.

What this PR adds is narrower than a missing capability. `pg_prewarm`
has no route at all, and its autoprewarm worker only runs when the
module is preloaded. For the other three, the field is an explicit
switch that does not require setting one of their tuning parameters,
even to its default value, just to get the library loaded. The two
routes combine rather than override: the operator merges this list with
the libraries it preloads on its own, so removing a module from
`sharedPreloadLibraries` does not unload it while a parameter under its
prefix is still set. The field description says so.

The distinction this PR draws is between a library *name* and a library
*path*. Nothing needs to be injected to preload these four:
`pg_stat_statements.so`, `auto_explain.so`, `pgaudit.so` and
`pg_prewarm.so` are already in `$libdir` in the image, and that
directory is on the read-only root filesystem, so it cannot be written
to. `dynamic_library_path` stays blocked, so `$libdir` remains the only
search path. A bare name from a fixed enum therefore has no way to reach
code that is not already in the image, which is the property the blanket
block was protecting.

The enum in `values.schema.json` is the primary guard and rejects a bad
value before rendering starts. The template carries the same list as a
backstop for renders that bypass schema validation, using the existing
fail-fast `SECURITY:` idiom from the parameter blocklist a few lines
below it. helm-unittest validates the schema on every render, so it
never reaches that backstop; the bats suite renders with
`--skip-schema-validation` instead. I checked that it fails when the
template condition is replaced with `false`, and when the template list
gains a name the enum does not have.

I verified the mechanism end to end on a live CloudNativePG 1.27.3
cluster rather than assuming it: with
`spec.postgresql.shared_preload_libraries` set, the operator writes
`shared_preload_libraries = 'pg_stat_statements'` into
`postgresql.conf`, `SHOW shared_preload_libraries` reports it, and
`SELECT ... FROM pg_stat_statements` returns rows. Adding a second
module to the list took effect too, and the CNPG instance manager
restarts PostgreSQL in place for it, with no pod restart. That restart
covers every instance, the primary included, so writes pause briefly.
The CRD documents the field as additive to the operator's own defaults,
so this does not clobber anything CNPG needs to preload itself.

Scope note: the four names are the modules in the image that are useful
to a tenant and safe to preload. Anything requiring a background worker
or a shipped-but-privileged module was deliberately left out, and the
enum is the single place to extend if that changes.

### Screenshots

No UI change.

### Downstream repositories

`packages/apps/postgres/values.schema.json` gains a field, which per the
trigger map reaches `cozystack/terraform-provider-cozystack`: its
postgres resource carries a hand-maintained schema and its own
expand/flatten pair, with no codegen from `values.schema.json`, so
`sharedPreloadLibraries` will be invisible to Terraform users until it
is added there by hand. The enum matters twice over there, because the
provider restates enums as `stringvalidator.OneOf` lists. I searched
that repository and found no open PR or issue covering it (the only open
PR is a dependabot Go module bump). I have not filed the follow-up, so I
am leaving the box unticked rather than claiming work that does not
exist. The same gap applies to `users.<name>.createRole` in #3505; one
follow-up there can cover both fields.

I walked the rest of the map against the diff and found nothing else: no
package is added, renamed or removed, no existing version enum changes,
no default changes, `release.prefix` and the output Secret and Service
names are untouched, and no CRD outside the regenerated
`packages/system/postgres-rd/cozyrds/postgres.yaml` is affected. The
`README.md` parameter table is regenerated here and postgres is already
in the website generator's app list, so the website path stays
automated.

- [ ] No downstream repository is affected by this change
- [ ] [cozystack/website](https://github.com/cozystack/website) -
follow-up:
- [ ]
[cozystack/terraform-provider-cozystack](https://github.com/cozystack/terraform-provider-cozystack)
- follow-up: not filed yet, see the note above
- [ ]
[cozystack/ansible-cozystack](https://github.com/cozystack/ansible-cozystack)
- follow-up:
- [ ] [cozystack/ccp](https://github.com/cozystack/ccp) - follow-up:
- [ ] [cozystack/talm](https://github.com/cozystack/talm) - follow-up:
- [ ] [cozystack/cozyhr](https://github.com/cozystack/cozyhr) -
follow-up:
- [ ] [cozystack/cozy-proxy](https://github.com/cozystack/cozy-proxy) -
follow-up:
- [ ]
[cozystack/cozystack-telemetry-server](https://github.com/cozystack/cozystack-telemetry-server)
- follow-up:
- [ ]
[cozystack/external-apps-example](https://github.com/cozystack/external-apps-example)
- follow-up:
- [ ] [cozystack/examples](https://github.com/cozystack/examples) -
follow-up:

### Release note

```release-note
feat(postgres): add `postgresql.sharedPreloadLibraries`, a closed allowlist of modules shipped in the PostgreSQL image (`pg_stat_statements`, `auto_explain`, `pgaudit`, `pg_prewarm`) that are preloaded at server start. It is the first way to preload `pg_prewarm`, and lets the other three be preloaded without setting one of their parameters, which CloudNativePG already treats as a request to preload them. The `shared_preload_libraries` parameter stays blocked: only bare names from the allowlist are accepted, never a path. Changing the list restarts PostgreSQL on every instance, the primary included.
```


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

* **New Features**
* Added optional PostgreSQL shared preload library configuration for
`pg_stat_statements`, `auto_explain`, `pgaudit`, and `pg_prewarm`.
* Preserves the configured library order. CloudNativePG may
automatically preload the first three libraries when their related
parameters are set; `pg_prewarm` must be enabled through this list.
* Changing the list restarts every PostgreSQL instance, including the
primary.
* **Validation**
* Rejects unsupported modules, absolute paths, and attempts to set
preload libraries through free-form parameters.
* **Documentation**
* Added configuration guidance covering supported libraries and restart
behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
2026-09-29 21:12:04 +03:00
2025-10-08 09:43:34 +05:00
2024-02-08 12:04:32 +01:00

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