stageflow-core 0.2.0

A DAG-based pipeline orchestration framework for building observable, composable stage pipelines

Stageflow

A DAG-based pipeline orchestration framework for building observable, composable stage pipelines in Python.

Features

• DAG Execution: Stages execute as soon as dependencies resolve, maximizing parallelism
• Fluent Pipeline Builder: Type-safe, composable pipeline definitions
• Interceptor Framework: Middleware pattern for cross-cutting concerns (timeouts, circuit breakers, tracing, metrics)
• Observable by Design: Structured events, correlation IDs, and logging built-in
• Protocol-Based Extension: Clean abstractions for persistence, configuration, and events
• Async-First: Built on asyncio for high-performance concurrent execution
• Zero Dependencies: Core library has no external dependencies

Installation

Latest release: v0.2.0

pip install stageflow

For development:

pip install stageflow[dev]

Quick Start

import asyncio
from stageflow import (
    Pipeline,
    Stage,
    StageContext,
    StageOutput,
    StageKind,
    PipelineTimer,
)
from stageflow.context import ContextSnapshot, RunIdentity
from stageflow.stages import StageInputs

# Define a stage
class GreetStage:
    name = "greet"
    kind = StageKind.TRANSFORM

    async def execute(self, ctx: StageContext) -> StageOutput:
        name = ctx.snapshot.input_text or "World"
        return StageOutput.ok(greeting=f"Hello, {name}!")

# Define another stage that depends on the first
class ShoutStage:
    name = "shout"
    kind = StageKind.TRANSFORM

    async def execute(self, ctx: StageContext) -> StageOutput:
        # Access output from dependency via StageInputs
        greeting = ctx.inputs.get_from("greet", "greeting", default="Hello!")
        return StageOutput.ok(shouted=greeting.upper())

# Build the pipeline
pipeline = (
    Pipeline()
    .with_stage("greet", GreetStage, StageKind.TRANSFORM)
    .with_stage("shout", ShoutStage, StageKind.TRANSFORM, dependencies=("greet",))
)

# Execute
async def main():
    graph = pipeline.build()
    snapshot = ContextSnapshot(run_id=RunIdentity(), input_text="World")
    base_inputs = StageInputs(snapshot=snapshot)
    ctx = StageContext(
        snapshot=snapshot,
        inputs=base_inputs,
        stage_name="pipeline_entry",
        timer=PipelineTimer(),
    )
    results = await graph.run(ctx)
    print(results["shout"].data["shouted"])  # "HELLO, WORLD!"

asyncio.run(main())

Core Concepts

Stages

A Stage is a unit of work with a defined input/output contract:

class Stage(Protocol):
    name: str
    kind: StageKind

    async def execute(self, ctx: StageContext) -> StageOutput: ...

Stage kinds categorize behavior:

• TRANSFORM - Change input form (STT, TTS, LLM)
• ENRICH - Add context (profile, memory, skills)
• ROUTE - Select execution path
• GUARD - Validate (guardrails, policy)
• WORK - Side effects (persist, assess)
• AGENT - Main interaction logic

Pipelines

Pipelines compose stages into a DAG using a fluent builder:

pipeline = (
    Pipeline()
    .with_stage("stt", SttStage, StageKind.TRANSFORM)
    .with_stage("enrich", EnrichStage, StageKind.ENRICH, dependencies=("stt",))
    .with_stage("llm", LlmStage, StageKind.TRANSFORM, dependencies=("enrich",))
    .with_stage("tts", TtsStage, StageKind.TRANSFORM, dependencies=("llm",))
)

Pipelines can be composed:

core_pipeline = Pipeline().with_stage(...)
voice_pipeline = core_pipeline.compose(
    Pipeline().with_stage("tts", TtsStage, StageKind.TRANSFORM, dependencies=("llm",))
)

Interceptors

Interceptors wrap stage execution for cross-cutting concerns:

from stageflow.interceptors import BaseInterceptor, InterceptorResult

class AuthInterceptor(BaseInterceptor):
    name = "auth"
    priority = 5  # Lower = runs first

    async def before(self, stage_name: str, ctx: PipelineContext) -> InterceptorResult | None:
        if not ctx.data.get("authenticated"):
            return InterceptorResult(stage_ran=False, error="Not authenticated")
        return None

    async def after(self, stage_name: str, result: StageResult, ctx: PipelineContext) -> None:
        pass

Built-in interceptors:

• TimeoutInterceptor - Per-stage timeouts
• CircuitBreakerInterceptor - Failure isolation
• TracingInterceptor - OpenTelemetry spans
• MetricsInterceptor - Stage duration/success metrics
• LoggingInterceptor - Structured JSON logging

Event Sinks

EventSink is a protocol for event persistence:

from stageflow import EventSink

class MyEventSink(EventSink):
    async def emit(self, *, type: str, data: dict | None) -> None:
        # Persist to your storage
        await db.insert("events", {"type": type, "data": data})

    def try_emit(self, *, type: str, data: dict | None) -> None:
        # Fire-and-forget variant
        asyncio.create_task(self.emit(type=type, data=data))

Architecture

Stageflow follows SOLID principles with a clear separation:

┌─────────────────────────────────────────────────────────────┐
│                        Your Application                       │
├─────────────────────────────────────────────────────────────┤
│  Adapters (implement protocols)                              │
│  - DatabaseEventSink                                         │
│  - PostgresRunStore                                          │
│  - EnvConfigProvider                                         │
├─────────────────────────────────────────────────────────────┤
│                     stageflow (core)                         │
│  ┌─────────┐  ┌─────────┐  ┌─────────────┐  ┌─────────┐   │
│  │ Pipeline │  │  Graph  │  │ Interceptors│  │ Events  │   │
│  └─────────┘  └─────────┘  └─────────────┘  └─────────┘   │
│  ┌─────────────────────────────────────────────────────┐   │
│  │                    Ports (protocols)                  │   │
│  │  EventSink | RunStore | ConfigProvider               │   │
│  └─────────────────────────────────────────────────────┘   │
└─────────────────────────────────────────────────────────────┘

Event Taxonomy

Stageflow emits structured events for observability:

Event Type	When
pipeline.created	Pipeline run initialized
pipeline.started	Execution begins
pipeline.completed	All stages finished
pipeline.failed	Unrecoverable error
pipeline.cancelled	Graceful termination
stage.{name}.started	Stage execution begins
stage.{name}.completed	Stage finished successfully
stage.{name}.failed	Stage threw error
stage.{name}.skipped	Conditional stage skipped

License

MIT

Contributing

Contributions welcome! Please read the contributing guide first.