Leoflow v0.1.0 — run your Airflow DAGs on a Go control plane (no Airflow in the hot path)

TL;DR — Leoflow v0.1.0 is the first stable release. You write standard
Apache Airflow 3.2 DAGs in Python; Leoflow's parser turns them into an immutable
dag.json using a structural shim that imports zero Airflow, the scheduler
(Go, no GIL) runs one pod per task, and the real Airflow provider operator
executes in the pod — so the control plane never imports Airflow, but your tasks
get full provider fidelity. Ships with 86 connection types, generic provider
operators + sensors (including reschedule-mode), and a Docker-free local Lite
edition that self-heals. GitHub: neochaotic/leoflow.

The bet

Airflow's execution model is right: a DAG of tasks, each task in its own pod
(KubernetesExecutor proved it). What's slow is the Python control plane — a
scheduler that imports your DAGs (and all their dependencies) into a GIL-bound
process, re-parses them constantly, and turns "add a provider" into a dependency-hell
negotiation across every DAG.

Leoflow keeps the model and rewrites the control plane in Go. No GIL. No Airflow
in the scheduling path. Each DAG is its own container image, so dependencies are
the DAG's problem, not the platform's. And the public API speaks Airflow 3.2, so
the real Airflow UI runs on top, unmodified.

The catch: if the control plane is Go and never imports Airflow, how does it read a
DAG written against the Airflow SDK? That's the shim — and it's the most interesting
piece of v0.1.0.

Here's the shape of it — your DAG becomes an immutable artifact, and a Go control
plane schedules it onto a pod per task:

You write real Airflow DAGs

No new DSL. This is a Leoflow DAG:

from airflow.sdk import DAG, task
from airflow.providers.standard.operators.bash import BashOperator

with DAG("sales", schedule="@daily"):
    pull = BashOperator(task_id="pull", bash_command="echo '[1, 2, 3]' > /tmp/raw.json")

    @task
    def transform() -> int:
        import json
        return len(json.load(open("/tmp/raw.json")))

    pull >> transform()

@task, >>, schedule, trigger rules, fan-in/fan-out, PythonOperator,
BashOperator — the constructs you already know. You compile it:

leoflow compile ./sales   # → dag.json + a container image

How the shim works (dag.py → dag.json, no Airflow imported)

Here's the trick (ADR 0024). The parser exec's your dag.py — but with a
structural stand-in for airflow on the import path. Pure standard library,
zero third-party deps. It reproduces exactly the attribute surface the compiler
reads, and nothing else:

Two consequences fall straight out of this design:

• An unsupported construct can't be faked. A from airflow.providers.foo... that the shim doesn't model raises ModuleNotFoundError — which the loader turns into a clear "not supported by Leoflow" error at compile time, never a silent half-run. Loud beats subtle.
• Task bodies never execute during parsing. @task calls only build the graph. Parsing a DAG can't trigger its side effects — the thing that makes Airflow's DAG-parsing both slow and dangerous.

So the control plane gets the graph without importing Airflow or installing a
single provider.

…but the real operator runs in the pod

Airflow's ecosystem is 1,500+ operators; modeling each in the shim would be a
treadmill. So Leoflow splits them (ADR 0040):

• A native fast path for the hottest few — bash, python, http, empty — which Leoflow runs with its own Go/runtime code. No Airflow in the pod at all; this is the "no Python in the hot path" part. A deliberate, growing whitelist.
• A generic path for the long tail. The shim's meta-path finder synthesizes any airflow.providers.<x>.{operators,sensors,transfers}.<Class> on demand and captures it — recording the operator's real dotted class path and its constructor kwargs, without the provider installed in the parser.

Then, at runtime, inside the task's own pod (where the provider is installed, via
the image), the agent does essentially:

import_string(dotted_class)(**captured_kwargs).execute(context)

The genuine Airflow operator runs, with the genuine provider, in an isolated pod —
while the control plane that scheduled it never imported either. Compile-time:
structure, dependency-free. Run-time: the real thing, in a pod. That seam is the
whole design.

Operators, sensors & 86 connectors

A provider operator is just an import. Anything outside the native fast path is
captured at compile time and runs for real in the pod — e.g. a SQL rollup against
your warehouse, its conn_id resolving to a managed connection:

from airflow.providers.common.sql.operators.sql import SQLExecuteQueryOperator
from airflow.sdk import DAG

with DAG("rollup", schedule="@daily", tags=["example"]):
    SQLExecuteQueryOperator(
        task_id="daily_rollup",
        conn_id="warehouse",   # a managed Connection (created in the UI)
        sql="insert into rollup select day, count(*) from events group by day",
    )

(BashOperator/PythonOperator/HttpOperator are the native path — Leoflow runs
those itself, no Airflow in the pod. Everything else takes the generic path above.)

Run it locally: in leoflow lite, add a warehouse Postgres connection
(Admin → Connections) plus events/rollup tables, then trigger the DAG — the
real SQLExecuteQueryOperator resolves the connection and writes the rollup. This
exact path is validated end-to-end.

Providers as a one-liner. A DAG declares what it needs; connectors: is sugar
(ADR 0038) that expands to the apache-airflow-providers-* packages and bakes them
into that DAG's image — no shared worker, no platform-wide dependency vote:

# leoflow.yaml
dag_id: sales
connectors: [postgres, http]      # → providers baked into THIS dag's image

86 connection types, generated from real Airflow (ADR 0039) so the connection
forms match field-for-field, are available in the UI. A managed connection is
delivered to the task pod as AIRFLOW_CONN_<ID> — the credential never lives in the
image:

@task
def load(rows: list[tuple]) -> None:
    import os, psycopg2
    dsn = os.environ["AIRFLOW_CONN_PG_TARGET"]   # a managed Connection, injected in-pod
    with psycopg2.connect(dsn) as conn:
        conn.cursor().executemany("INSERT INTO cats VALUES (%s, %s)", rows)

Sensors, including reschedule mode. A mode='reschedule' sensor releases its
pod between checks:

from airflow.providers.standard.sensors.date_time import DateTimeSensor

DateTimeSensor(task_id="wait_until_six", target_time="{{ ds }}T06:00:00+00:00",
               mode="reschedule")

A sensor waiting six hours isn't holding a pod for six hours: each not-ready poke
surfaces up_for_reschedule, frees the pod, and is re-dispatched when it's time to
check again.

Lite: zero to a local grid, Docker-free

leoflow lite is the local edition — no Kubernetes, no cloud:

leoflow lite --postgres managed     # embedded Postgres, no Docker required

It scaffolds a starter DAG, brings up an embedded Postgres, starts the control
plane, and serves the Airflow 3.2 UI at localhost:8088 — hot-reloading on every
save. v0.1.0 hardened it to be resilient:

• Docker wedged? It keeps working. If the Docker daemon is present but unresponsive, Lite falls back to the managed (Docker-free) Postgres instead of failing on docker compose up.
• It self-heals its state. Reusing a metadata DB used to leave "ghost" DAGs and stale import errors you couldn't remove from the UI. Now, on boot, Lite reconciles the registered DAGs against your workspace — deregistering what's gone and clearing orphan import errors — fail-safe (it never wipes on an unreachable control plane). It's gated by an end-to-end CI test so it can't silently regress.

Leoflow vs an Airflow control plane

Why use it

• You already write Airflow DAGs — keep them. The shim reads standard airflow.sdk; your operators run for real in the pod.
• You're tired of dependency hell — each DAG owns its image; adding a provider to one DAG never touches another.
• You want the control plane off the critical path — Go, no GIL, no DAG imports, no parse-time side effects.
• You want the Airflow UI without the Airflow scheduler — v0.1.0 serves the real 3.2 UI on a Go core.
• You want a real local loop — leoflow lite, no Kubernetes, that doesn't fall over when your Docker does.

Status

v0.1.0 is the first stable release (the v0.1.0-rc.N series soaked and promoted —
SemVer carries the maturity; no alpha/beta). It ships the shim, 86 connectors,
generic provider operators + sensors (reschedule included), the resilient Lite
edition, and the embedded Airflow 3.2 UI. dbt-native rendering is next (v0.1.1).

Try it in 30 seconds:

curl -fsSL https://raw.githubusercontent.com/neochaotic/leoflow/main/install.sh | sh
leoflow lite

→ github.com/neochaotic/leoflow — point
leoflow lite at a DAG and watch it light up the grid. Tell us where it bites.

Apache 2.0. Thanks for reading.