thermograph/infra/terraform/README.md

# Thermograph — Terraform (host provisioning)

Terraform that **provisions and configures VPS hosts** and hands the app off to
`docker compose`, which pulls the published app image (built + pushed by the app
repo's CI) and runs it — no app source is ever built or checked out on a host.
By default it does *not* create servers: `modules/thermograph-host` is
SSH-provisioner-driven against a host that already exists. An optional
`modules/gcp-host` can additionally *create* the VM on GCP first (see "GCP
scaffold" below) — scaffold-only today, no live resources until you opt in.

## What it manages

One reusable module (`modules/thermograph-host`) is instantiated per
**(host, environment)** pair via `for_each` (`main.tf`'s `local.all_hosts`,
merging `var.hosts` — SSH-managed, already-existing boxes — with any
`var.gcp_hosts` Terraform created itself). `var.hosts` is keyed by HOST, not by
environment, because **vps2 alone runs two environments** (prod and beta) as
separate Docker Swarm stacks on the same box — see the `hosts` variable's file
header in `variables.tf` for why that stopped being "one entry = one
environment" and what still needs to change in `main.tf` to consume the new
shape (flagged there as a `TODO(cutover)`). This config manages **two VPS
hosts**, three environments, today:

| host   | environment | VPS                                       | branch | domain                 | notes                                       |
|--------|-------------|--------------------------------------------|--------|------------------------|----------------------------------------------|
| `vps1` | `dev`       | `75.119.132.91`                             | `dev` (of the APP repos — see `backend_image_tag` / `frontend_image_tag`) | none (mesh-only)       | Also hosts Forgejo, Grafana/Loki/Alloy, emigriffith.dev — not Terraform-managed |
| `vps2` | `prod`      | 48 GB / 12-core box (`169.58.46.181`)        | `main` | `thermograph.org`      | Caddy TLS (this module owns `/etc/caddy/Caddyfile`); sized up (8/8/4/16g) |
| `vps2` | `beta`      | the SAME box as prod (`169.58.46.181`)      | `main` | none (see below)       | Separate Swarm stack + checkout, shares prod's TimescaleDB instance on a separate database/role |

Only ONE environment per host may set a `domain`: the module installs a full
`/etc/caddy/Caddyfile`, and a second `terraform apply` with its own `domain` set
would silently overwrite the first's site instead of adding to it (there is no
merge). Prod claims that slot on vps2 today, so beta's public reverse-proxy (if
and when `beta.thermograph.org` is exposed) has to be a site block in vps2's
shared, hand-maintained Caddy config instead — the same pattern
`deploy/forgejo/docker-stack.yml` already uses to put `git.thermograph.org` in
front of Forgejo's loopback port on vps1, alongside that box's own Caddy-fronted
`emigriffith.dev`.

Each environment's own checkout on disk (`app_dir`, `git_branch`) is **this
infra repo**, not the app repo — the "branch" column above is which app-repo
tag an environment is meant to track conceptually; the actual pinned versions
are `var.hosts[*].environments[*].backend_image_tag` / `frontend_image_tag`
(e.g. `"sha-<12 hex>"` each — the app is two separately-published images,
`admin_emi/thermograph-backend/app` and `admin_emi/thermograph-frontend/app`), since the
host has no app checkout to derive a tag from. `app_dir` is required with no
default specifically so vps2's two environments can never collide on the same
checkout path (prod: `/opt/thermograph`, beta: `/opt/thermograph-beta`). The
LAN-laptop dev rehearsal (`make dev-up`) is **out of scope here** — it's a
local-only compose overlay, not this Terraform-managed `dev` environment.

Per (host, environment), over SSH provisioners, Terraform:

- installs Docker + the compose plugin if missing;
- configures a `ufw` firewall (22/80/443 always; on a host with **no** domain it also
  opens the app port `8137`);
- ensures the git checkout at `app_dir` exists (clones **this repo** on a fresh box)
  and resets it to the host's `git_branch`;
- renders `/etc/thermograph-topology.env` from Terraform variables (non-secret sizing
  only — `WORKERS`/`APP_CPUS`/`DB_CPUS`/`DB_MEMORY`/etc.), then runs
  `deploy/render-secrets.sh` (from that same freshly-synced checkout) to render
  `/etc/thermograph.env` from the SOPS+age vault — **Terraform itself never sees or
  carries an app secret** (see "Secrets" below);
- for a host **with** a domain, installs a rendered Caddyfile and reloads Caddy;
- brings the stack up on the explicit per-service tags (exports `BACKEND_IMAGE_TAG` /
  `FRONTEND_IMAGE_TAG` for the compose file): `docker login` to the registry,
  `docker compose <-f each compose file> pull backend frontend`, then
  `... up -d --remove-orphans`, running docker as root with both env files sourced;
- health-checks `http://127.0.0.1:8137/`.

A change to the rendered topology env, the compose files, the branch, the app image
tag, or the sizing flips the `null_resource` trigger and re-runs the provisioners on
next apply.

## GCP scaffold (no live resources)

`modules/gcp-host` can create a GCE VM (+ a dedicated VPC, subnet, and a firewall
opening 22/80/443) instead of assuming the host already exists — see `main.tf`'s
`module.gcp_vm`. It contributes *nothing* to provisioning: its only output
(`external_ip`) feeds into the exact same `thermograph-host` module every
SSH-managed host uses, so there's one provisioning path regardless of how a
host came to exist. `var.gcp_hosts` defaults to `{}`, so by default no
`google_*` resource is ever planned and the `google` provider is never
invoked — `terraform plan`/`validate` succeed with no GCP credentials
configured at all. To actually use it: populate an entry in
`terraform.tfvars` (see the commented example in
`terraform.tfvars.example`) and authenticate via `gcloud auth
application-default login` or `GOOGLE_APPLICATION_CREDENTIALS`. This is the
same create-then-provision composition a future Proxmox module (the
architecture doc's longer-term target — see §6/§9 there) would use.

### Container sizing is env-driven

`docker-compose.yml` reads `WORKERS`, `APP_CPUS`, `DB_CPUS`, and `DB_MEMORY` from the
environment (defaults `4 / 4 / 2 / 8g`, identical to before). Terraform sets them per
host through `/etc/thermograph-topology.env`, so the big prod box can run larger caps
without a compose edit. The Postgres *internal* memory budget (`shared_buffers`,
`effective_cache_size`, `work_mem`, `maintenance_work_mem`) is derived from the same
`DB_MEMORY` by `deploy/db/init/20-tuning.sh` — so raising `db_memory` scales the
container cap and the tuning together (prod 16g → shared_buffers 4 GB). The tuning
applies on a fresh DB volume; on an existing volume re-run it by hand (see the script
header).

## Prerequisites

- Terraform >= 1.6 (v1.15 is installed).
- SSH key access to **both** hosts as a **sudo-capable** user (the live boxes use the
  dedicated `agent` account, `~/.ssh/thermograph_agent_ed25519` — see
  `deploy/provision-agent-access.sh`). Point `ssh_private_key_path` at that key (`~`
  is expanded).
- The hosts are Debian/Ubuntu with `apt` and outbound internet (Docker/Caddy installs
  pull from the network). Docker may already be present — installs are conditional.
- For the `prod` host: DNS for `thermograph.org` must point at the new box before apply,
  or Caddy's first-request cert issuance will fail.

## Use

```sh
cd terraform
cp terraform.tfvars.example terraform.tfvars   # then edit: real IPs + secrets
terraform init
terraform plan
terraform apply
```

Target one host with `-target='module.host["prod"]'` if you want to apply to just one
(the module's `for_each` key changes once `main.tf` is updated to flatten `var.hosts`'s
new per-host `environments` map — see the `TODO(cutover)` on the `hosts` variable in
`variables.tf` — at which point the key for beta becomes something like
`module.host["vps2-beta"]`, not `module.host["beta"]`).

## Secrets

App secrets (`POSTGRES_PASSWORD`, `THERMOGRAPH_AUTH_SECRET`, VAPID keys,
`REGISTRY_TOKEN`, Discord/SMTP credentials, …) are **not** Terraform variables
— they live in the git-native SOPS+age vault at `../deploy/secrets/*.yaml`
(committed, encrypted) and are rendered into `/etc/thermograph.env` at deploy
time by `../deploy/render-secrets.sh`, which the provisioner's deploy step
runs from the freshly-synced checkout. Terraform only renders the non-secret
`/etc/thermograph-topology.env` (sizing/routing). See
`../deploy/secrets/README.md` to rotate a secret or add a new one — it's a
`sops edit` + commit + deploy, no Terraform apply involved.

`om_rclone_conf` (object-storage bucket credentials for the self-hosted ERA5
archive) is the one exception still supplied via Terraform, in
`terraform.tfvars` — folding it into the vault too is a reasonable future
step, not done here.

## Local state

The backend is **local**: `terraform.tfstate` is written next to the config.
It's gitignored (`terraform/.gitignore` and the root `.gitignore`) — keep it
off shared disks and back it up somewhere private. `terraform.tfvars` is
likewise gitignored (it may carry a `repo_url` credential and always carries
`om_rclone_conf`); only `terraform.tfvars.example` (dummy values) is
committed. `.terraform.lock.hcl` **is** committed so provider versions are
pinned across machines.

## WARNING — applying against live prod

`terraform apply` runs `remote-exec` **on the server**: it resets the checkout to the
branch, renders topology config + secrets, and runs `docker compose pull && up -d`
(pulling the pinned `backend_image_tag` / `frontend_image_tag` and recreating
containers — a brief app restart).
Against the live production host this is a real deploy. Review the plan, apply in a
maintenance window, and prefer `-target` to touch one host at a time.

This is **separate from the Postgres data cutover** in `deploy/POSTGRES-MIGRATION.md`.
Terraform provisions the host and starts the stack; it does **not** migrate the
SQLite→Postgres accounts data. Sequence them deliberately: for a first cutover on a
host, follow the migration doc's freeze/backup/copy steps around the point where
Terraform brings the stack up — don't let Terraform recreate containers mid-migration.

## Assumptions / notes

- **beta has no public domain here, and can't without a different Caddy strategy.**
  With `compose_files = ["docker-compose.yml"]` the app binds `127.0.0.1:8137`
  (loopback), so opening the port in `ufw` alone does not expose it — and setting
  `domain` on beta the way prod does would make this module overwrite the SAME
  `/etc/caddy/Caddyfile` prod's apply just installed (see the table above). Reach
  beta via an SSH tunnel, or front it with a site block in vps2's own
  hand-maintained Caddy config (outside Terraform), the same way Forgejo's
  `git.thermograph.org` reaches Forgejo's loopback port on vps1.
  `COOKIE_SECURE` is auto-set to `0` when there's no domain (a Secure
  cookie is never sent over plain HTTP) and `1` behind Caddy TLS.
- The rendered Caddyfile only reverse-proxies the app. The repo's `deploy/Caddyfile`
  additionally serves the `emigriffith.dev` portfolio and legacy redirects; those are
  host-specific and not templated here.
- Provisioner-based by design: the hosts already exist, so this is not a
  create-from-scratch cloud config. Re-applying is idempotent (installs are guarded,
  `git reset --hard`, compose `up` reconciles).