arthur/server/settings.py

"""Settings for arthur's backend.

It serves three things and they are three different kinds of thing, which is most
of what there is to know about this file:

  THE PAGE. One template, which replaced `frontend/public/index.html` at step 9.
  It pulls the shadow-cljs bundle out of staticfiles, so `manage.py runserver` and
  `shadow-cljs watch app` are the whole dev loop with nothing copying files
  between them.

  THE DOCUMENT (tier 1). Small, authored, in the database.

  THE BLOBS (tiers 2 and 3). Large, immutable, content-addressed, on disk under
  `var/blobs`. Never in the database, and never in a migration.
"""
from pathlib import Path
import os

BASE_DIR = Path(__file__).resolve().parent.parent

# Dev default. The deployment that needs a real one will set it, and until there
# is a deployment, a checked-in placeholder that says so beats a checked-in secret
# that does not.
SECRET_KEY = os.environ.get("DJANGO_SECRET_KEY", "dev-only-not-a-secret-arthur")
DEBUG = os.environ.get("DJANGO_DEBUG", "1").lower() in {"1", "true", "yes"}
ALLOWED_HOSTS = os.environ.get(
    "DJANGO_ALLOWED_HOSTS", "localhost,127.0.0.1,[::1]"
).split(",")
CSRF_TRUSTED_ORIGINS = [
    origin for origin in os.environ.get("DJANGO_CSRF_TRUSTED", "").split(",")
    if origin
]

INSTALLED_APPS = [
    # First, so `runserver` is daphne's and serves the websocket too.
    "daphne",
    "channels",
    "django.contrib.admin",
    "django.contrib.auth",
    "django.contrib.contenttypes",
    "django.contrib.sessions",
    "django.contrib.messages",
    "django.contrib.staticfiles",
    "clips",
]

MIDDLEWARE = [
    "django.middleware.security.SecurityMiddleware",
    "whitenoise.middleware.WhiteNoiseMiddleware",
    "django.contrib.sessions.middleware.SessionMiddleware",
    "django.middleware.common.CommonMiddleware",
    "django.middleware.csrf.CsrfViewMiddleware",
    "django.contrib.auth.middleware.AuthenticationMiddleware",
    "django.contrib.messages.middleware.MessageMiddleware",
]

# Process-local, like the consumer's ROOMS: one worker. docs/architecture.md
# names the move — Redis — for the day there is a second.
CHANNEL_LAYERS = {"default": {"BACKEND": "channels.layers.InMemoryChannelLayer"}}

ROOT_URLCONF = "server.urls"
WSGI_APPLICATION = "server.wsgi.application"
ASGI_APPLICATION = "server.asgi.application"

TEMPLATES = [
    {
        "BACKEND": "django.template.backends.django.DjangoTemplates",
        "DIRS": [],
        "APP_DIRS": True,
        "OPTIONS": {
            "context_processors": [
                "django.template.context_processors.request",
                "django.contrib.auth.context_processors.auth",
                "django.contrib.messages.context_processors.messages",
            ],
        },
    },
]

# WAL and a real busy timeout, because a save is a BURST of writes: one analysis,
# then a block per dense channel, then the leaves. Under the default rollback
# journal and a 5-second timeout, the block uploads of one save fail with
# "database is locked" — which surfaces in the page as a 500 with nothing wrong,
# and in the browser suite as a document that will not save. WAL lets readers and
# one writer proceed at once, and the timeout makes the writers queue instead of
# giving up. The client serialises its uploads as well (see events/project), so
# this is the belt to that braces.
#
# The ceiling this has is the one docs/architecture.md already names for tl's
# process-local ROOMS: one writer. It is a single-worker arrangement, and moving
# off it is a Postgres URL rather than a change to anything above this line.
DATABASES = {
    "default": {
        "ENGINE": "django.db.backends.sqlite3",
        "NAME": os.environ.get("DJANGO_DB_PATH", str(BASE_DIR / "db.sqlite3")),
        "OPTIONS": {
            "timeout": 20,
            "init_command": "PRAGMA journal_mode=WAL; PRAGMA synchronous=NORMAL;",
        },
    }
}

AUTH_PASSWORD_VALIDATORS = []
LANGUAGE_CODE = "en-gb"
TIME_ZONE = "UTC"
USE_I18N = True
USE_TZ = True

DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"

# --- static -----------------------------------------------------------------
#
# Two roots, and the second is the interesting one. `static/` is where
# shadow-cljs writes the bundle (`:output-dir "../static/arthur/js"`), so the
# build lands straight in the staticfiles tree. The vendored MediaPipe is served
# under the prefix `mediapipe/` from where it already lives in `frontend/public/`
# — 26MB of wasm and model that has no business being copied into a second place
# in the tree, and that `collectstatic` picks up from there.
STATIC_URL = "/static/"
STATICFILES_DIRS = [
    BASE_DIR / "static",
    ("mediapipe", BASE_DIR / "frontend" / "public" / "mediapipe"),
]
STATIC_ROOT = BASE_DIR / "var" / "static"
STORAGES = {
    "default": {"BACKEND": "django.core.files.storage.FileSystemStorage"},
    "staticfiles": {"BACKEND": "whitenoise.storage.CompressedStaticFilesStorage"},
}

# --- blobs ------------------------------------------------------------------
#
# Tiers 2 and 3 live here, named by the sha256 of their own bytes, fanned out two
# levels so no directory holds a hundred thousand entries. Deliberately NOT under
# `static/`: a blob is served by a view that can set immutable cache headers and
# refuse a path that is not a hash, and `collectstatic` has no business walking
# gigabytes of frames.
BLOB_ROOT = Path(os.environ.get("DJANGO_BLOB_ROOT", str(BASE_DIR / "var" / "blobs")))

# The port the browser suite expects by default, and not 8777, which is still the
# old JS tool's under `serve.py`. Both are meant to run side by side.
DEV_PORT = 8778