# `pgbackrest` role — Postgres backup + WAL archive to MinIO/S3

Wires pgBackRest into the pg_auto_failover formation: full backup weekly, differential daily, WAL continuously to a MinIO bucket. Backups encrypted at rest with `aes-256-cbc`. The dr-drill script (`scripts/dr-drill.sh`) restores into an ephemeral Incus container and asserts the data round-trips — runs weekly via systemd timer, exposes a textfile metric for Prometheus.

## Cadence

| job  | when                  | schedule (defaults)              | metric source             |
| ---- | --------------------- | -------------------------------- | ------------------------- |
| full | weekly Sun 02:00 UTC  | `pgbackrest_schedule_full`       | systemd journald          |
| diff | daily Mon-Sat 02:00   | `pgbackrest_schedule_diff`       | systemd journald          |
| WAL  | continuous (per file) | postgres `archive_command`       | postgres logs + pgBackRest |
| drill| weekly Sun 04:00 UTC  | `pgbackrest_drill_schedule`      | textfile collector .prom  |

## RPO / RTO

- **RPO** ≈ 1 minute. `archive_timeout=60` forces a WAL switch + push every minute even when traffic is low. Worst-case data loss on a primary's death: the last 60s of WAL that hadn't shipped yet.
- **RTO** ≤ 30 min. The dr-drill restore runs end-to-end in ~10-20 min on the lab; production should match given the same backup size.

## Vault setup

Three secrets — never committed:

```bash
# group_vars/postgres_ha.vault.yml (encrypted)
vault_pgbackrest_s3_key: "<MinIO access key>"
vault_pgbackrest_s3_key_secret: "<MinIO secret key>"
vault_pgbackrest_cipher_pass: "<random 64-char passphrase>"
```

```bash
ansible-vault encrypt infra/ansible/group_vars/postgres_ha.vault.yml
```

The role's first task asserts the placeholders are gone — applying with the placeholder defaults aborts loud rather than rolling out a misconfigured archive.

## Repo wiring

```ini
repo1-type        = s3
repo1-s3-endpoint = minio.lxd:9000
repo1-s3-bucket   = veza-pgbackrest
repo1-s3-uri-style = path             # MinIO speaks path-style by default
repo1-cipher-type = aes-256-cbc
```

Bucket created by the `minio_distributed` role (W3 day 12). Until then operators bootstrap with:

```bash
mc alias set veza-minio https://minio.lxd:9000 <ACCESS> <SECRET>
mc mb veza-minio/veza-pgbackrest
```

## Operations

```bash
# Backup status — most recent full + diff + WAL window:
sudo -u postgres pgbackrest --stanza=veza info

# Manual full backup (use sparingly — it's bandwidth-heavy):
sudo systemctl start pgbackrest-full.service

# Tail the most recent backup log:
sudo journalctl -u pgbackrest-full.service -n 200 --no-pager

# Verify the archive pipeline is healthy (last WAL ship time):
sudo -u postgres pgbackrest --stanza=veza check
```

## Restore — the dr-drill

```bash
bash scripts/dr-drill.sh
```

Sequence:

1. Read latest backup label via `pgbackrest info`
2. Launch ephemeral Incus container `pg-restore-drill`
3. Install postgres + pgbackrest inside, render the same `pgbackrest.conf` (read-only mode against the same bucket)
4. `pgbackrest --stanza=veza restore` to recover
5. Start postgres
6. Connect, run `SELECT count(*) FROM users` — must be > 0 (proves the seed data round-tripped)
7. Write `veza_backup_drill_*` metrics to `pgbackrest_drill_metrics_file`
8. Tear down the container (or keep it for inspection if `--keep` is passed)

The metrics file is scraped by node_exporter's `--collector.textfile.directory`. Prometheus alert `BackupRestoreDrillFailed` (added in `config/prometheus/alert_rules.yml`) fires when the last successful drill is older than 8 days, OR when the most recent run reported a non-zero exit code.

## What this role does NOT cover

- **Off-site replica** — the bucket is single-region MinIO. v1.1+ adds Bunny.net or B2 as a secondary repo (`repo2-*`).
- **Point-in-time UI** — restore is CLI-only via `--type=time`. Operator-driven, no admin dashboard.
- **Logical export** — for legal/RGPD requests, `pg_dump` of the relevant rows is a separate path; the binary backups in this role aren't designed to be partially extracted.