kajenn-orchestra

Status: Beta · version 0.2.0.

Orchestration for kajenn: one mountable application, SpaApplication, and a supervised pool of worker processes behind it. Every page a user opens is served by the same process and his state lives in that process's memory, so the second request finds what the first one built.

A commander in the server process owns the indexes — whose a connection is, which connection a page belongs to, where each user lives — and one group per worker grammar owns the processes. A group launches one worker at boot and grows only when a real user finds none that can admit him; nothing in the recipe says how many workers there are.

A user reaches another process through one path: he is held, his state is written to the freezer on disk, his placement is cleared, and his next request wakes him wherever the placement lands. Idleness, CPU pressure and the departure of a worker all take that same path. Nothing replicates between processes; the only shared state is one dictionary the commander owns and every worker reaches by call.

The setpoints of a group — memory shares, admission thresholds, the idle horizon — are composed defaults ⊕ recipe ⊕ profile ⊕ environment and can be replaced on a running pool, validated whole or refused whole.

kajenn_orchestra imports kajenn; kajenn never imports kajenn_orchestra. The core loads the front by class reference from the configuration recipe. The modules of kajenn this package may import are listed in kajenn_imports.txt and checked by tools/import_graph.py in the pre-commit hook.

Based on genropy history and genro-modules.

Installation

pip install kajenn-orchestra

kajenn is installed with it. Beside a kajenn checkout, [tool.uv.sources] in pyproject.toml points at ../kajenn:

uv venv .venv
uv pip install -p .venv/bin/python -e ".[dev,docs,internals]"

A minimal pool

# worker.py
from kajenn_orchestra.orchestration.spa_worker import SpaWorker


class SiteWorker(SpaWorker):
    def __init__(self, name, **kwargs):
        super().__init__(name, **kwargs)
        self.wsgi_app = my_wsgi_site


# config.py
from kajenn.config import AsgiConfigBuilder
from kajenn_orchestra.spa_app import SpaApplication


class ServerConfiguration(AsgiConfigBuilder):
    default_config = False

    def main(self, root):
        cfg = root.configuration()
        cfg.server(host="127.0.0.1", port=8000)
        front = cfg.applications().application(
            code="site", mount="", app_class=SpaApplication
        )
        commander = front.orchestration().commander(
            frozen_users_path="/var/spa/frozen", instance_dir="/run/kajenn"
        )
        commander.groups(default="standard").group(
            name="standard",
            entry_module="kajenn_orchestra.orchestration.worker_entry",
            worker_class="worker:SiteWorker",
        )

kajenn serve ./config.py

The front answers on /, mints nothing, and writes the spa_connection_id cookie with the connection id the hosted site named while serving.

Project

• Documentation: https://kajenn-orchestra.readthedocs.io/en/latest/
• kajenn documentation: https://kajenn.readthedocs.io/en/latest/
• Internals dossier: internals/, read with mkdocs serve
• Organization: https://github.com/kajenn-org

License

Apache License 2.0, copyright Softwell S.r.l.