fenrir-framework 2.3.5

A hybrid Python web framework combining Flask, FastAPI, Bottle, Falcon, and Sanic

Fenrir Web Framework

Fenrir is a state-of-the-art, high-performance, hybrid Python web framework built on top of modern ASGI specifications. It elegantly merges the best programming paradigms from Python's most popular web frameworks (Flask, FastAPI, Sanic, Falcon, and Bottle) into a single unified workspace, powered locally by the premium Asteri application server.

Whether you prefer the automatic Pydantic validation of FastAPI, the seamless context-locals of Flask, the raw class-based speed of Falcon, or the robust background task model of Sanic, Fenrir allows you to leverage them all simultaneously in the same codebase.

---

📦 Installation

Install directly from PyPI:

pip install fenrir-framework

Or install with Redis support for distributed sessions and rate limiting:

pip install fenrir-framework[redis]

Or install in development mode by cloning the repository:

git clone https://github.com/IshikawaUta/fenrir.git
cd fenrir
pip install -e .

---

🌟 Key Features

• ⚡ High-Speed ASGI Core: Extremely low-overhead routing and handler pipeline, achieving massive request throughput.
• 🔺 Trie-Based Routing: O(k) route matching where k = path depth, instead of O(n) linear scan. Handles 1000+ routes efficiently.
• 🧩 Framework Hybridization:
  • FastAPI Paradigm: Native Pydantic v2 data validation, Annotated type decorators, automated parameter resolution (Query, Path, Header, Cookie, Body), dynamic dependency injection (Depends), and automated response_model serialization.
  • Flask Paradigm: Thread/Task-safe context locals (request, g, session), Jinja2 template rendering (render_template), and request teardown hooks.
  • Falcon Paradigm: Class-based resource controllers (on_get, on_post), before/after hooks, and in-place response mutation.
  • Sanic Paradigm: Global sys.modules patching (install_sanic_compat()), standard response helpers (json, text, html, raw, redirect), lifecycle listeners (before_server_start, etc.), and a background event scheduler (app.add_task).
  • Bottle Paradigm: Built-in WSGI-to-ASGI wrapper and legacy mount adapter (app.mount_wsgi()) to run old WSGI applications at ASGI speeds.
• 📖 Auto-Generated OpenAPI Docs: Interactive Swagger UI (/docs) and ReDoc (/redoc) instantly generated from your Pydantic schemas and route metadata.
• 🔌 Modern Communications: Out-of-the-box support for WebSockets (with authentication) and Server-Sent Events (SSE).
• 🔐 WebSocket Authentication: WebSocketTokenAuth dependency for token-based WebSocket authentication via headers or query parameters.
• 🗄️ Connection Pooling: Built-in generic ConnectionPool and DatabasePool with health checks, retry logic, and automatic connection recycling.
• 🌐 HTTP/2 Push: HTTP2Push utility for server push with Link headers and auto-push decorators.
• ⏱️ Advanced Rate Limiting: Per-IP or per-user rate limiting with optional Redis backend for distributed deployments.
• 📦 Streaming Request Body: stream_body() method for memory-efficient processing of large uploads without buffering.
• 🗜️ Optimized GZip Compression: Default compression level 6 (optimal CPU/ratio trade-off) instead of level 9.
• 🛠️ Premium CLI Tooling: Visual route tables, interactive app shell, in-memory benchmarking suite, project scaffolding, and environment system inspection.
• 🐍 Python 3.8–3.13 Compatible: Full backward compatibility ensured via typing_extensions polyfills for Annotated, get_origin, get_args; and a contextvars-aware asyncio.to_thread shim.

---

🚀 Quick Start (The Hybrid Power)

Here is a simple example (demo_app.py) showcasing how Flask, FastAPI, Falcon, and Sanic styles coexist harmoniously in a single application:

import logging
from pydantic import BaseModel
from fenrir import (
    Fenrir, Blueprint, request, g, Depends, Query, Header,
    render_template, Response, Form, File, UploadFile,
    WebSocket, WebSocketDisconnect
)

logging.basicConfig(level=logging.INFO)
logger = logging.getLogger("demo")

# Initialize the Hybrid App
app = Fenrir(title="Fenrir Hybrid Demo", version="2.3.5")

# --- 1. FastAPI-Style Validation & DI ---
class UserRegister(BaseModel):
    username: str
    email: str
    age: int

async def verify_api_key(x_api_key: str = Header(default=None)):
    if x_api_key != "super-secret-key":
        logger.warning("Invalid API key attempt")
    return x_api_key

# --- 2. Flask-Style Routing & Context-Locals ---
@app.get("/")
async def home():
    name = request.args.get("name", "Fenrir Developer")
    return render_template("index.html", name=name)

# --- 3. Falcon-Style Class-Based Resources ---
class ItemResource:
    async def on_get(self, req, resp, item_id: int):
        resp.status = 200
        resp.media = {"item_id": item_id, "style": "Falcon Resource"}

app.add_route("/items/<item_id:int>", ItemResource())

# --- 4. Sanic-Style Listeners & Background Tasks ---
@app.listener("before_server_start")
async def setup_db(app_instance):
    logger.info("Initializing mock database...")

@app.middleware("request")
async def log_request(req):
    logger.info(f"Incoming: {req.method} {req.path}")
    g.user_role = "guest"  # Share state using Flask-style 'g'

# Run with Asteri ASGI server
if __name__ == "__main__":
    app.run(host="127.0.0.1", port=8000, workers=2)

---

🔺 Trie-Based Routing

Fenrir v2.3.5 uses a trie-based routing index for O(k) route matching, where k is the path depth. This is significantly faster than linear O(n) matching when you have many routes.

from fenrir import Fenrir

app = Fenrir()

# These routes are indexed in a trie for fast lookup
@app.get("/api/v1/users")
async def list_users(): ...

@app.get("/api/v1/users/<int:user_id>")
async def get_user(user_id: int): ...

@app.get("/api/v1/posts/<int:post_id>/comments")
async def get_comments(post_id: int): ...

# Route matching is O(k) where k = number of path segments
# /api/v1/users/42 → checks: api → v1 → users → 42 (parametric)

---

🔐 WebSocket Authentication

Authenticate WebSocket connections using tokens from headers or query parameters:

from fenrir import Fenrir, WebSocket, Depends
from fenrir.security import WebSocketTokenAuth

app = Fenrir()
auth = WebSocketTokenAuth()

@app.websocket("/ws")
async def websocket_handler(websocket: WebSocket, token: str = Depends(auth)):
    await websocket.accept()
    await websocket.send_text(f"Authenticated with token: {token}")
    while True:
        data = await websocket.receive_text()
        await websocket.send_text(f"Echo: {data}")

---

🗄️ Connection Pooling

Built-in connection pooling for databases and external services:

from fenrir import Fenrir
from fenrir.pool import ConnectionPool

app = Fenrir()

# Create a connection pool
pool = ConnectionPool(
    create_func=lambda: create_engine("sqlite:///db.sqlite3"),
    close_func=lambda engine: engine.dispose(),
    min_size=2,
    max_size=10,
)

@app.get("/users")
async def list_users():
    async with pool.acquire() as conn:
        result = conn.execute("SELECT * FROM users")
        return {"users": [dict(row) for row in result]}

---

🌐 HTTP/2 Push

Proactively push resources to clients before they request them:

from fenrir import Fenrir
from fenrir.http2 import HTTP2Push

app = Fenrir()
push = HTTP2Push()

@app.get("/")
async def index():
    return push.push(
        "<html><link rel='stylesheet' href='/static/style.css'></html>",
        push_paths=["/static/style.css", "/static/app.js"],
    )

---

⏱️ Advanced Rate Limiting

Per-IP or per-user rate limiting with optional Redis backend:

from fenrir import Fenrir
from fenrir.middleware import RateLimitMiddleware

app = Fenrir()

# Per-IP rate limiting
app.add_middleware(RateLimitMiddleware, max_requests=100, window_seconds=60)

# Per-user rate limiting
def user_key(scope):
    for k, v in scope.get("headers", []):
        if k == b"x-user-id":
            return v.decode("latin-1")
    client = scope.get("client")
    return client[0] if client else "unknown"

app.add_middleware(RateLimitMiddleware, key_func=user_key)

# Distributed rate limiting with Redis
import redis.asyncio as aioredis
redis_client = aioredis.Redis()
app.add_middleware(RateLimitMiddleware, redis_client=redis_client)

---

📦 Streaming Request Body

Process large uploads efficiently without buffering the entire body:

from fenrir import Fenrir, Request

app = Fenrir()

@app.post("/upload")
async def upload(request: Request):
    total_bytes = 0
    async for chunk in request.stream_body(chunk_size=65536):
        total_bytes += len(chunk)
        # Process each chunk without loading entire body into memory
    return {"bytes_received": total_bytes}

---

💻 CLI Command Reference

Fenrir comes packed with a high-fidelity, visually rich command-line tool. Start the CLI by executing fenrir or python -m fenrir.cli.

1. fenrir run

Serve your application locally. Powered by Asteri, supporting dynamic multiprocessing, worker management, and live hot-reloading.

fenrir run demo_app:app --port 8000 --dev

• Flags:
  • -H, --host: Host bind address (default: 127.0.0.1).
  • -p, --port: Port number (default: 8000).
  • -w, --workers: Number of concurrent workers (default: 1).
  • -d, --dev / --reload: Active development mode with auto-reload.

2. fenrir routes

Print a beautiful, colorized structural table of all registered HTTP endpoints, methods, matching handlers, and associated blueprints.

fenrir routes demo_app:app

3. fenrir shell

Instantly spawn an interactive python shell pre-configured with all key framework classes and context loaded (app, request, g, Response, Blueprint, etc.).

fenrir shell demo_app:app

4. fenrir bench

Perform in-memory framework benchmarking directly over ASGI using HTTPX. Eliminates network noise and tests raw pipeline speed under loaded constraints.

fenrir bench demo_app:app -i 1000 -t 5 -p / -m GET

5. fenrir new

Scaffold a complete, cleanly structured new Fenrir project directory in seconds with a premium responsive UI out of the box.

fenrir new my_new_project
cd my_new_project
fenrir run app.py --dev

6. fenrir info

Inspect the environment including Python details, OS details, Pydantic/Asteri versions, active compatibility layers, and route statistics.

fenrir info demo_app:app

---

🧪 Comprehensive Test Suite

Fenrir is thoroughly covered by an automated test suite comprising 568 tests validating every single component, including the new trie-based routing, streaming body, connection pooling, HTTP/2 push, WebSocket authentication, and rate limiting features. The suite runs automatically via GitHub Actions on every push across Python 3.8 – 3.13.

Run the test suite locally:

PYTHONPATH=. pytest -v

Output:

=============================== 568 passed, 1 skipped in 6.72s ===============================

---

🔄 Changelog

v2.3.5 — Bug Fix & Changelog Update

• Updated changelog to accurately reflect version history
• All version references synchronized across codebase

v2.3.4 — Bug Fix Release

• Fix server crash: fenrir run was passing wrong app_path (fenrir.app:_active_app) to Asteri worker, causing 'NoneType' object is not callable
• Fix Python 3.8 support: replaced asyncio.to_thread with fenrir.compat.to_thread shim
• Updated all version strings across codebase

v2.3.3 — 🚫 Retracted

• Published with incomplete version updates, superseded by v2.3.4

v2.3.2 — Architecture & Performance Upgrade

Major architecture improvements, new features, and performance optimizations:

Architecture Improvements

• Trie-Based Routing: Replaced O(n) linear route matching with O(k) trie-based routing. Route lookup now scales with path depth, not total route count.
• Context Vars Migration: Removed sys._fenrir_active_app hack, replaced with proper contextvars.ContextVar for thread/async-task-safe app context.

New Components

• Connection Pooling (fenrir.pool): Generic ConnectionPool and DatabasePool with health checks, retry logic, automatic connection recycling, and configurable pool sizes.
• HTTP/2 Push (fenrir.http2): HTTP2Push utility for server push with Link headers, auto-push decorators, and resource type guessing.
• WebSocket Authentication (fenrir.security): WebSocketTokenAuth dependency for token-based WebSocket authentication via headers or query parameters.

New Features

• Streaming Request Body: request.stream_body() method for memory-efficient processing of large uploads without buffering.
• Per-User Rate Limiting: key_func parameter in RateLimitMiddleware for custom rate limiting keys (user ID, API key, etc.).
• Distributed Rate Limiting: Redis backend support for RateLimitMiddleware using sliding window algorithm.

Performance Optimizations

• GZip Compression Level: Default compresslevel changed from 9 to 6 for optimal CPU/ratio trade-off.
• Redis Rate Limiter: Uses time.monotonic() instead of time.time() for clock-safe operation, with unique IDs to prevent collisions.
• Deprecated API Fix: Replaced deprecated asyncio.get_event_loop() with asyncio.get_running_loop() in WSGI adapter.

Bug Fixes

• Fixed missing import sys in app.py that silently broke root_path detection.
• Fixed stale sys._fenrir_active_app references in views.py and templating.py.
• Fixed inconsistent version strings across pyproject.toml, __init__.py, and app.py.
• Fixed unused import asyncio in falcon.py.
• Removed private Semaphore._value access from Pool.stats.

New Exports

• RouteTrie, WebSocketTokenAuth, ConnectionPool, DatabasePool, HTTP2Push

v2.2.2 — Major Feature Update

New middleware, session backends, pagination, and more:

New Middleware (fenrir.middleware)

• CORSMiddleware: Full CORS support for HTTP and WebSocket with configurable origins, methods, headers, credentials, and max-age.
• GZipMiddleware: Automatic gzip compression for responses above a configurable size threshold.
• RequestIDMiddleware: Auto-generates unique request IDs or forwards client-provided IDs via configurable header.
• RateLimitMiddleware: Sliding-window rate limiter per client IP with configurable limits and block status code.

New Session Backends (fenrir.sessions)

• InMemorySessionInterface: In-memory session storage with TTL expiration, suitable for single-process apps and testing.
• RedisSessionInterface: Redis-backed session storage with support for both sync (fakeredis) and async (redis.asyncio) clients. Install with pip install fenrir-framework[redis].

New Pagination Utilities (fenrir.pagination)

• PaginationParams: Pydantic model for query parameters (page, page_size, sort_by, sort_order).
• paginate(): Utility to paginate SQLAlchemy-style query results with metadata.
• paginate_dict(): Utility to paginate lists of dictionaries.

New Features

• WebSocket per-route timeout: @app.websocket("/ws", timeout=5.0) raises WebSocketTimeout if no message received within the timeout.
• Multiple response models per status: response_models={200: SuccessModel, 404: ErrorModel} applies different models based on the actual response status code.

Improvements

• ASGI middleware stack is now built once and cached, with automatic invalidation when new middleware is added.
• Zero deprecation warnings across the entire test suite (528 tests).

v1.2.2 — Logo & Favicon Patch

High-quality logo assets and resolved CLI template favicon issues:

• High-Resolution Logo: Updated logo.png asset to a high-fidelity image for sharper rendering in documentation and templates.
• Favicon Resolution: Ensured favicon is correctly rendered and copied during project scaffolding (fenrir new) from the package assets.

v1.2.1 — Packaging & Asset Integration Patch

Logo and favicon assets are now properly included in the package distribution:

Logo Asset Packaging

• Issue: fenrir new command failed to copy logo and favicon files when creating new projects outside the main repository.
• Root cause: Logo files (logo.png, logo.jpg) were stored in the repository root, not within the fenrir/ package directory, so they were not included when the package was installed via PyPI.
• Fix:
  • Moved logo.png and logo.jpg from repository root to fenrir/ package directory.
  • Added [tool.setuptools.package-data] configuration in pyproject.toml to include image files: fenrir = ["logo.png", "logo.jpg"].
  • Updated fenrir/cli.py cmd_new() function to look for logos in the fenrir package directory first, with fallbacks for development mode.
• Result: All tests pass (528 unit tests). fenrir new now works correctly in all environments.

v1.1.1 — Python 3.8–3.10 Full Compatibility Patch

Five test failures on Python 3.8 CI were identified and patched:

1. RuntimeError: Working outside of request context (session, redirect in sync handlers)

• Root cause: loop.run_in_executor() does not propagate contextvars by default. Sync route handlers using session[...] or redirect() lost the request context when moved into the executor thread.
• Fix: fenrir/compat.py — polyfill now calls contextvars.copy_context().run(func) instead of passing func directly to the executor.

2. AssertionError: {'user': None} != {'user': 'Alice'} (Annotated[str, Header()])

• Root cause: typing.get_origin(typing_extensions.Annotated[...]) returns None on Python 3.8, so Annotated parameters were silently ignored during dependency resolution.
• Fix: fenrir/compat.py — export get_origin/get_args from typing_extensions (which correctly handles its own Annotated). fenrir/dependencies.py and fenrir/openapi.py now import these from fenrir.compat.

3. AssertionError: {'content_type': ''} != {'content_type': 'text/plain'} (file upload)

• Root cause: python-multipart < 0.0.21 (installed on Python 3.8–3.10 CI runners) did not pass content_type into File.__init__, so file.content_type did not exist.
• Fix: fenrir/request.py — intercepts the parser's on_header_field/on_header_value/on_headers_finished callbacks to capture the Content-Type of each multipart part before the File object is constructed, and injects it as a fallback.

4. AssertionError: 'target' == '/nested/target' (relative redirect)

• Resolved as a side-effect of fix #1 (contextvars propagation restores request.path inside the executor thread).

5. CI timeout on Python 3.9 (gevent build)

• The Python 3.9 job was cancelled mid-build because compiling gevent took too long. This is an infrastructure concern, not a code issue; no code change required.

v1.1.0 — CI/CD & Centering Fix

• Added GitHub Actions workflow for automated testing across Python 3.8–3.13.
• Fixed centering of PROJECT CREATED SUCCESSFULLY badge and logo in scaffolded template.
• Added RFC 7231 HEAD method compliance.
• Added itsdangerous and python-multipart as explicit core dependencies.

v0.1.0 — Initial Release

• Core ASGI framework with Flask, FastAPI, Sanic, Falcon, and Bottle hybridization.
• 528 automated unit tests.
• Premium CLI tooling (run, routes, shell, bench, new, info).
• Auto-generated OpenAPI/Swagger documentation.
• WebSocket and Server-Sent Events support.

---

📜 License

Fenrir is open-sourced software licensed under the MIT License.