claviron-python

CPython embedded in a Rust host. This package owns PyO3 and the interpreter boundary: one CPython 3.15 per process, its venv and the application's environment. With asgi it runs ASGI applications: lifespan, streaming HTTP and message sessions. It does not start a runner, HTTP listener or process supervisor.

The gufi runner uses this engine over Orbit. Hosts that own routing and lifecycle can depend on the engine directly. It succeeds claviron-asgi, which gets no further releases, and is not published yet.

[dependencies]
claviron-python = { version = "0.2", features = ["asgi"] }

Ownership

asgi::PythonApplication declares the module:attribute target, module paths and optional virtual environment. boot() starts the application-loop thread and returns its RunningPythonApplication owner only after lifespan startup completes. Its cloneable handle accepts streaming HTTP and message sessions.

The host retains the running owner while requests are admitted. It stops its ingress and drains accepted work before calling shutdown(), which waits for accepted exchanges, ASGI lifespan shutdown and the loop thread. Drop uses the same shutdown path. Boot and shutdown may block; async hosts must run these ownership transitions on their blocking executor. No implicit grace deadline or forced Python-task cancellation is introduced.

routing::PythonService is a Tower-compatible HTTP adapter. Its shared handle cell follows the host-managed application generation; an empty cell returns 503. routing::request_scope preserves Claviron's accepted connection and trusted-proxy context when adapting message handshakes.

Initialization owns one process-wide CPython 3.15 interpreter and its selected environment. This package provides no independent virtual-environment or subinterpreter isolation inside a process. Application stop/restart runs ASGI lifespan without finalizing CPython or evicting imported modules.

In a host

With edge enabled, the registration call installs the Python application and the python: route factory on Edge.

claviron_python::register(state)?;

Hosts that supply their own site registry can select backend and call claviron_python::backend::register(site) alongside runtime registration.

# python.yaml
name: app                             # its name in the application manager
target: app:app
module_path: apps/python
venv: .venv
env:
  APP_SECRET_KEY: ${APP_SECRET_KEY}   # expanded from the host's environment and env files
  APP_DEBUG: "0"
# env_file: config/app.env            # further values, with deployment variants
# frameworks: [django]                # shown by management clients
# icon: django                        # a symbolic icon code, never a path

# a host in vhost.yaml
routes:
  /api:
    python: {}

python.yaml names one application, because a process has one interpreter and one environment. A second application runs in its own process and joins over Orbit, which is what the gufi runner does. An interpreter does not change its environment, so a changed python.yaml takes a restart. Each worker boots its own interpreter; a master boots none.

Where the host registers Claviron's application manager, the application is listed and controlled as python:<name>, with request mode asgi. Stopping it runs ASGI lifespan shutdown, and its routes answer 503 until it starts again; starting it boots it from the python.yaml published at that moment. Its modules stay imported in the interpreter, so a restart runs a new lifespan with the code already loaded: changed code takes a new worker.

The application's os.environ is its own: the values env and env_file declare, beside only the runtime essentials the host keeps, such as PATH and HOME. ${NAME} expands from the host's environment and its .env files, but the host's variables themselves are not passed on. The values are written into the interpreter's mapping, never into the process environment, so other runtimes in the process do not see them and a child process started without an explicit env does not inherit them. A C library that reads its settings with getenv() does not see them either; pass such settings to it from Python.

The path reaches the application as the client sent it. An HTTP/1.1 WebSocket goes to the application when the host's transport allows h1.upgrade, and is refused with 403 otherwise. WebSocket over HTTP/2 or HTTP/3 is not served from a route yet.

With the webtransport feature, a route names the paths a WebTransport session may open on, under its mount, and the host's transport allows h3.webtransport:

routes:
  /:
    python:
      webtransport: [/ws/echo]

Each reliable bidirectional stream of a session is one ASGI WebSocket connection, with scope["transport"] set to "webtransport". The stream carries one record per message, as a stream relayed over Orbit does:

u8 kind (1 text, 2 binary, 8 close) | u32 length (little endian) | payload

The application decides the first stream before the session is answered, so a refusal stays an HTTP status; a later stream it refuses is reset. Without the feature, a route that names paths is refused when it is prepared.

Native Python capabilities

The native Python namespace is claviron, including invocation and counters, plus optional broadcast, logging and Django Channels capabilities. The broadcast, log and django features select their native adapters; the host supplies the matching services. They do not install a Python compatibility package or change the ASGI protocol.

The module exists only inside the host process. Add this repository's stubs/ directory to your editor's stub search path; it holds type declarations only.

Building

Select CPython 3.15 with PYO3_PYTHON or PyO3 configuration. This package owns ABI validation and publishes the shared-library directory to a direct host's build script as DEP_CLAVIRON_PYTHON_LIB_DIR. The gufi runner forwards the same directory under its existing DEP_GUFI_PYTHON_LIB_DIR key.

Existing engine tests live under tests/. The Python driver checks can also run directly, without booting a Rust host:

python3.15 -B tests/python/test_asgi_driver.py
python3.15 -B tests/python/test_native_module.py