Paul Payne
e438f45b54
Model:
- Drop `requires` from ProgramSpec; requires is now deployment-only.
Collapse Requirement to {ref, bind} with kind defaulting to "deployment"
(drop the unused `version`). System-package preconditions stay on the
program as `system_dependencies`, synthesized into {kind: system} for the
functional check. relations.py/deploy.py read only the deployment's requires.
- create.py seeds a stack's substrate dependency onto the deployment, not the
program. Docs + tests updated.
UI:
- Add a `requires` editor (useRequires) on service, job, and static detail
pages — edit service→service deps (ref + optional bind env var).
- Restore the gateway route table "Open" column: a kind-aware in-app link to
each route's deployment.
- Reformat the reach control: name baked into each option
(localhost:PORT (local) / <name>.<domain> (internal) / <name>.<pubdomain> (public)).
- Services page: sort statics in with systemd services by name, add a
search + kind-filter bar mirroring the programs page.
102 lines
5.0 KiB
Markdown
102 lines
5.0 KiB
Markdown
# Relationships: requires, repos, and derived predicates
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How castle models the relationships between **programs**, **deployments**, and
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**repos** — and answers questions like *"is this functional?"*, *"is it fresh?"*,
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*"is it deployed?"* — with the smallest possible amount of stored state.
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## The governing principle
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> **Predicates are always derived. Encode only what is not derivable.**
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A *predicate* is a question we ask about a program or deployment: `functional?`,
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`fresh?`, `deployed?`. None of these are ever stored — each is a **function** over
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data castle already has (git, config, the registry). When a predicate can't be
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answered from derived data, find the one missing datum and ask: is it about the
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**thing** (a node property) or about a **relationship** (an edge property)? Encode
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*only* that datum. Everything else stays computed.
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This is the same instinct as `kind` (derived from `manager`) — we don't store what
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we can compute, and a relationship that proves real and stable in the derived graph
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is a candidate to *promote* into a first-class concept. Diagnostic → evidence →
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abstraction, in that order.
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## Entities
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- **program** — the software catalog entry.
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- **deployment** — a program realized on this node (`kind` derived from `manager`).
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- **repo** — a git working copy. **Derived** from `git rev-parse --show-toplevel`
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on each program's source; several programs sharing one toplevel is a *monorepo*.
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Never stored.
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## Encoded preconditions: `requires` + `system_dependencies`
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Everything we were calling "substrate", "wiring", or "dependency" reduces to
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preconditions ("A must have B to be functional"), encoded on the layer each belongs
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to. The relationship model unifies them into one requirement set with a typed target;
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the **kind fixes the meaning and the check**:
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| kind | source (where encoded) | means | checked by |
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|------|------------------------|-------|-----------|
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| `deployment` | the **deployment**'s `requires` | another deployment must **exist** | registry / config |
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| `system` | the **program**'s `system_dependencies` | the host package/binary must be **installed** | `which` / `dpkg` |
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A **deployment** declares the deployments it depends on. `kind` defaults to
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`deployment`, so an entry is just a `ref` (+ optional `bind`):
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```yaml
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# deployments/<kind>/astro.yaml
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requires:
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- ref: astro-guru
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- ref: supabase
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- { ref: litellm, bind: LITELLM_URL } # bind: project the target's URL into env
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```
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A **program**'s host-package preconditions stay on the program as
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`system_dependencies` (a plain list of package names); the model synthesizes the
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`{kind: system}` requirements from it for the `functional?` check. This split keeps
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each precondition on its natural layer — a deployment-ref is node-level wiring
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(belongs on the deployment), a host package is intrinsic to the software (belongs on
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the program). There is no `requires` on the program, and no `kind: system` written
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into a deployment's `requires`.
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Only encode a `requires` edge that is **not derivable** and that **castle itself
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must traverse** for an operation (status, bring-up order, group ops). Do **not**
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duplicate what another layer already owns — systemd `Requires=`/`After=` for unit
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ordering, uv/pnpm for build graphs. This is *castle's* slice, uncoupled from any
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one package ecosystem.
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### Env is derived *from* `requires`, never scraped *into* it
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Reading dependencies out of env strings is unstable (formats vary; a static
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frontend's API URL is baked into its bundle and invisible). The stable direction is
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the reverse: from an encoded `{ref, bind}` deployment requirement castle **generates**
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the wiring env — it knows the target's address (`<ref>.<domain>` / its port) and
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projects it into the consumer's env, optionally under the var named by `bind`. Same
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move as `${public_url}`, one step further. Dependency → env, never env → dependency.
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## Derived predicates
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Computed on demand from encoded `requires` + git + registry; nothing stored:
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- **`functional?`** — every `requires` is satisfied (system installed, deployment
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exists). The unmet ones *are* the node's status (`doctor`/`status`).
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- **`fresh?`** — the program's repo is at latest and clean (git status).
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- **`deployed?`** — the deployment is active in the registry.
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New predicates are just new functions over the same preconditions — there is
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nothing to "unify" in storage.
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## What's encoded vs derived (the whole surface)
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| datum | source | stored? |
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|-------|--------|---------|
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| repo / monorepo | git toplevel | derived |
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| `fresh?` / `deployed?` / `functional?` | git / registry / requires | derived |
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| env wiring for a dependency | the `requires` edge + target address | derived |
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| fan-in ("widely depended-on") | count of requires | derived |
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| a **non-derivable** requirement (frontend→backend, host package) | — | **encoded** (`requires`) |
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| the env var to bind a dep's URL to, when non-conventional | — | **encoded** (`requires[].bind`) |
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Every irreducible found so far is an **edge** (a relationship); no new **node**
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property has been needed yet — a sign the encoded surface stays tiny.
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