Metadata-Version: 2.5
Name: arkitekt-service
Version: 1.9.0
Summary: What a service of an Arkitekt hub is made with: the contract its image answers the installer, its declaration to rekuest, and its hook agent
Author-email: jhnnsrs <jhnnsrs@gmail.com>
License: MIT
Requires-Python: <4,>=3.12
Requires-Dist: django>=5
Requires-Dist: httpx>=0.27
Requires-Dist: joserfc>=1.7
Requires-Dist: pydantic-settings>=2.3
Requires-Dist: pydantic>=2.7
Requires-Dist: pyyaml>=6
Provides-Extra: koherent
Requires-Dist: koherent>=4.1; extra == 'koherent'
Description-Content-Type: text/markdown

# arkitekt-service

What a service of an [Arkitekt](https://arkitekt.live) hub is made with. Three parts, for three
different things a service process does:

| | |
|---|---|
| `arkitekt_service.contract` | What the service's **image** answers the hub's installer: what it needs, its own config written from the hub's facts, its migrations and upgrades. |
| `arkitekt_service.service` | What the service **is** to the hub's rekuest: the structures it hosts and the signals it emits. |
| `arkitekt_service.hook` | What can be **done** in its process: a HookAgent, whose actions rekuest reaches over HTTP. |

They share `arkitekt_service.trust` — no secrets between services: every instance signs with
its own key and the hub vouches for the public halves — and nothing else. A process uses any of
them without the others.

```
pip install arkitekt-service
```

## The contract

Everything that is done with a service's image goes through one command in it:

```
arkitekt-service                      # what it is, needs and offers, and what to run in it (JSON)
arkitekt-service serve                # become the service: serve, and nothing else
arkitekt-service debug                # the same, with the development server
arkitekt-service run migrate          # bring its database to this release, then its setup
arkitekt-service run <job>            # any other job it offers: plan, superuser, upgrade, its own
arkitekt-service standalone           # run migrate, then serve: one image, run on its own
arkitekt-service render               # this release's config, from the hub's facts
arkitekt-service check                # does this release read a config as written?
```

An installer (Konstruktor) then needs to know the hub, and nothing about a service that the
service's image does not say. How a release spells its config, which keys it renamed, how it
is started, what it has to do to its data — all of that ships in the image, with the code it
belongs to. Exit code `78` is a release's own refusal (facts it cannot be configured from, a
setting it does not read, a job it does not offer), with the reason on stderr.

### The image says what it is

The image's own command is the first of these:

```dockerfile
CMD ["arkitekt-service", "describe"]
```

So an installer asks by running the image with no command, and assumes nothing of what is
inside: every other command it runs is one the answer named. A service written in another
language takes part by printing the same description as its own command. Whoever starts the
image by hand gets the description too, and beside it, on stderr, a note saying that nothing
is being served and what to run instead.

What the description says:

- `identifier`: what the service is registered as, and what a client asks for.
- `needs`, `offers`, `requires`: what a hub has to provide, and what other services are
  wired to.
- `serve` and `debug`: what a container of the image runs to serve, in production and in
  development. An installer writes the one that applies as the service's command.
- `jobs`: what can be run in the image beside its start, by name, each with the command that
  runs it. `migrate` is every service's, and lists the jobs it runs as its setup
  (`includes`). An operator runs any of them again by name, e.g. `konstruktor job run mikro
  ensureadmin`, which is `arkitekt-service run ensureadmin` in a container of the image.
- `prepare`: which job brings the database to the release (`migrate`).
- `render`: what writes the release's config from the hub's facts.
- `sidecars`: what runs beside the service as an image of its own: one it does not run
  without (rekuest's takt, named from the service's image), or an `optional` one it drives
  on a hub that has the use for it (Lok's mesh control server).

### A container serves; a job prepares

A service's container does one thing: serve. `arkitekt-service serve` becomes the server and
does nothing before that. Everything its database needs first is `run migrate`: wait for the
database, apply the release's migrations, then run the jobs the service named as its `setup`
(an admin account, seeded rows), all in one process. Whoever starts the service runs it as a
job of its own, once per build, before the first start and before an update's:

```
docker compose run --rm --no-deps mikro arkitekt-service run migrate
```

or, in a compose file that has no installer, as a service the server waits for:

```yaml
mikro-migrate:
  image: jhnnsrs/mikro:7
  command: arkitekt-service run migrate
mikro:
  image: jhnnsrs/mikro:7
  command: arkitekt-service serve
  depends_on:
    mikro-migrate:
      condition: service_completed_successfully
```

A container that merely restarts then does none of it.

`arkitekt-service standalone` is the two together, for the one case where that is what is
wanted: a single image run on its own — a developer's compose file, a quick look at a
release. It prepares, then serves, and serves nothing if preparing failed. Nothing that
manages a stack uses it.

### Declaring a service

A service declares itself in one module, named by `ARKITEKT_SERVICE` in its Dockerfile:

```python
from arkitekt_service.contract import JSON, Contract, Description, Facts, Job, Needs, Offers, Start, blocks


def render(facts: Facts) -> dict[str, JSON]:
    document = blocks.server(facts)  # django, postgres, redis, authentikate
    document["datalayer"] = blocks.datalayer(facts, "media", "zarr")
    return document


contract = Contract(
    description=Description(name="mikro", identifier="live.arkitekt.mikro", needs=Needs(storage=["media", "zarr"])),
    settings=Settings,
    render=render,
    # How it is started. There is no script beside this: `arkitekt-service serve` becomes it.
    serve=Start(("daphne", "-b", "0.0.0.0", "-p", "80", "mikro_server.asgi:application")),
    debug=Start(("python", "manage.py", "runserver", "0.0.0.0:80")),
    # What else can be run in the image, by name, and which of it `migrate` runs as setup.
    jobs={"ensureadmin": Job(("ensureadmin",), "Create the operator account the config names")},
    setup=("ensureadmin",),
)
```

The hub's facts (`arkitekt_service.contract.facts`) and a service's description
(`arkitekt_service.contract.description`) are versioned documents; an image refuses facts it
does not understand rather than dropping them.

## A service, and a hook agent

```python
from arkitekt_service.service import Descriptor, Service, organization_of
from arkitekt_service.hook import HookAgent

service = Service("mikro", description="Microscopy data")
dataset = service.structure(ArrayDataset, "@mikro/arraydataset", descriptors=[Descriptor("@mikro/n_channels", "INT")], describe=array_descriptors)
service.model_signal(dataset, organization=organization_of())

agent = HookAgent("mikro", description="mikro's housekeeping")


@agent.action
def reembed_stale(organization: str) -> dict:
    """Re-embed stale rows."""
    ...


urlpatterns = [..., *service.urls, *agent.urls]
```

A service says what exists; an agent says what can be done. Neither knows the other.

## Development

```
uv sync
uv run pytest                                          # the contract and the service
uv run pytest tests/hook --ds=hook_project.settings    # the hook agent: a process that is no service
uv run basedpyright
```

Releases are cut from conventional commits on `main` (tag-only, like the other Arkitekt
packages) and uploaded to PyPI.
