├── .github └── workflows │ ├── publish.yml │ └── test.yml ├── .gitignore ├── LICENSE ├── README.md ├── asgi_proxy ├── __init__.py └── __main__.py ├── setup.py └── tests ├── conftest.py └── test_asgi_proxy.py /.github/workflows/publish.yml: -------------------------------------------------------------------------------- 1 | name: Publish Python Package 2 | 3 | on: 4 | release: 5 | types: [created] 6 | 7 | permissions: 8 | contents: read 9 | 10 | jobs: 11 | test: 12 | runs-on: ubuntu-latest 13 | strategy: 14 | matrix: 15 | python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"] 16 | steps: 17 | - uses: actions/checkout@v4 18 | - name: Set up Python ${{ matrix.python-version }} 19 | uses: actions/setup-python@v5 20 | with: 21 | python-version: ${{ matrix.python-version }} 22 | cache: pip 23 | cache-dependency-path: setup.py 24 | - name: Install dependencies 25 | run: | 26 | pip install '.[test]' 27 | - name: Run tests 28 | run: | 29 | pytest 30 | deploy: 31 | runs-on: ubuntu-latest 32 | needs: [test] 33 | steps: 34 | - uses: actions/checkout@v4 35 | - name: Set up Python 36 | uses: actions/setup-python@v5 37 | with: 38 | python-version: "3.13" 39 | cache: pip 40 | cache-dependency-path: setup.py 41 | - name: Install dependencies 42 | run: | 43 | pip install setuptools wheel twine build 44 | - name: Publish 45 | env: 46 | TWINE_USERNAME: __token__ 47 | TWINE_PASSWORD: ${{ secrets.PYPI_TOKEN }} 48 | run: | 49 | python -m build 50 | twine upload dist/* 51 | 52 | -------------------------------------------------------------------------------- /.github/workflows/test.yml: -------------------------------------------------------------------------------- 1 | name: Test 2 | 3 | on: [push, pull_request] 4 | 5 | permissions: 6 | contents: read 7 | 8 | jobs: 9 | test: 10 | runs-on: ubuntu-latest 11 | strategy: 12 | matrix: 13 | python-version: ["3.9", "3.10", "3.11", "3.12", "3.13"] 14 | steps: 15 | - uses: actions/checkout@v4 16 | - name: Set up Python ${{ matrix.python-version }} 17 | uses: actions/setup-python@v5 18 | with: 19 | python-version: ${{ matrix.python-version }} 20 | cache: pip 21 | cache-dependency-path: setup.py 22 | - name: Install dependencies 23 | run: | 24 | pip install '.[test]' 25 | - name: Run tests 26 | run: | 27 | pytest 28 | 29 | -------------------------------------------------------------------------------- /.gitignore: -------------------------------------------------------------------------------- 1 | .venv 2 | __pycache__/ 3 | *.py[cod] 4 | *$py.class 5 | venv 6 | .eggs 7 | .pytest_cache 8 | *.egg-info 9 | .DS_Store 10 | dist 11 | build 12 | -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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You can use it like this: 20 | 21 | ```python 22 | from asgi_proxy import asgi_proxy 23 | 24 | app = asgi_proxy("https://datasette.io") 25 | ``` 26 | Now `app` is an ASGI application that will proxy all incoming HTTP requests to the equivalent URL on `https://datasette.io`. 27 | 28 | The function takes an optional second argument, `log=` - set this to a Python logger, or any object that has `.info(msg)` and `.error(msg)` methods, and the proxy will log information about each request it proxies. 29 | 30 | It also takes a `timeout=` option, which defaults to `None` for no timeout. This can be set to a floating point value in seconds to enforce a timeout on requests that are being proxied. 31 | 32 | ## CLI tool 33 | 34 | You can try this module out like so: 35 | 36 | ```bash 37 | python -m asgi_proxy https://datasette.io 38 | ``` 39 | You may need to `pip install uvicorn` first for this to work. 40 | 41 | Alternatively, use [uv](https://github.com/astral-sh/uv) like this: 42 | ```bash 43 | uv run --with uvicorn --with asgi-proxy-lib python -m asgi_proxy https://datasette.io 44 | ``` 45 | 46 | This will start a server on port 8000 that proxies to `https://datasette.io`. 47 | 48 | Add `-p PORT` to specify a different port, `--timeout 3` to set a timeout, `--verbose` to see debug logging, and `--host 127.0.0.1` to listen on a different host (the default is `0.0.0.0`). 49 | 50 | ## Development 51 | 52 | To contribute to this library, first checkout the code. Then create a new virtual environment: 53 | 54 | cd asgi-proxy-lib 55 | python -m venv venv 56 | source venv/bin/activate 57 | 58 | Now install the dependencies and test dependencies: 59 | 60 | pip install -e '.[test]' 61 | 62 | To run the tests: 63 | 64 | pytest 65 | -------------------------------------------------------------------------------- /asgi_proxy/__init__.py: -------------------------------------------------------------------------------- 1 | import httpx 2 | from urllib.parse import urlparse 3 | 4 | 5 | def asgi_proxy(backend, log=None, timeout=None): 6 | backend_host = urlparse(backend).netloc 7 | 8 | async def asgi_proxy(scope, receive, send): 9 | assert scope["type"] == "http" 10 | 11 | method = scope["method"] 12 | path = scope["path"] 13 | query_string = scope["query_string"].decode() 14 | 15 | # Forward headers 16 | headers = {k.decode().lower(): v.decode() for k, v in scope.get("headers", [])} 17 | # Replace host header 18 | headers["host"] = backend_host.encode() 19 | # Ensure we don't get compressed content 20 | headers["accept-encoding"] = "identity" 21 | 22 | url_bits = [backend, path] 23 | if query_string: 24 | url_bits.extend(("?", query_string)) 25 | url = "".join(url_bits) 26 | 27 | # Receive request body if any 28 | more_body = True 29 | body = b"" 30 | while more_body: 31 | message = await receive() 32 | body += message.get("body", b"") 33 | more_body = message.get("more_body", False) 34 | 35 | async with httpx.AsyncClient(timeout=timeout) as client: 36 | try: 37 | # Stream it, in case of long streaming responses 38 | async with client.stream( 39 | method, url, data=body or None, headers=headers 40 | ) as resp: 41 | if log: 42 | log.info(f"Request: {method} {url}") 43 | log.info(f"Response: {resp.status_code} {resp.reason_phrase}") 44 | # Start the response 45 | await send( 46 | { 47 | "type": "http.response.start", 48 | "status": resp.status_code, 49 | "headers": [ 50 | (k.encode(), v.encode()) 51 | for k, v in resp.headers.items() 52 | ], 53 | } 54 | ) 55 | # Stream the content 56 | try: 57 | # aiter_raw not aiter_bytes because we don't want 58 | # content decoding to have been applied 59 | async for chunk in resp.aiter_raw(): 60 | await send( 61 | { 62 | "type": "http.response.body", 63 | "body": chunk, 64 | "more_body": True, 65 | } 66 | ) 67 | except Exception as e: 68 | # The client has disconnected 69 | if log: 70 | log.info( 71 | f"Client disconnected: {e.__class__.__name__}: {e}" 72 | ) 73 | await send({"type": "http.response.body", "more_body": False}) 74 | return 75 | 76 | await send({"type": "http.response.body", "more_body": False}) 77 | except httpx.TimeoutException as ex: 78 | if log: 79 | log.error(f"Timeout error occurred: {ex.__class__.__name__}: {ex}") 80 | await send( 81 | { 82 | "type": "http.response.start", 83 | "status": 504, 84 | } 85 | ) 86 | await send( 87 | { 88 | "type": "http.response.body", 89 | "body": b"Gateway timeout", 90 | "more_body": False, 91 | } 92 | ) 93 | except Exception as ex: 94 | # Handle any errors during the request 95 | if log: 96 | log.error(f"An error occurred: {ex.__class__.__name__}: {ex}") 97 | await send( 98 | { 99 | "type": "http.response.start", 100 | # Generic gateway error 101 | "status": 502, 102 | } 103 | ) 104 | await send( 105 | { 106 | "type": "http.response.body", 107 | "body": b"Bad gateway", 108 | "more_body": False, 109 | } 110 | ) 111 | 112 | return asgi_proxy 113 | -------------------------------------------------------------------------------- /asgi_proxy/__main__.py: -------------------------------------------------------------------------------- 1 | from . import asgi_proxy 2 | import argparse 3 | import sys 4 | 5 | 6 | if __name__ == "__main__": 7 | try: 8 | import uvicorn 9 | except ImportError: 10 | print("Install uvicorn with: pip install uvicorn") 11 | sys.exit(1) 12 | 13 | parser = argparse.ArgumentParser(description="Start a proxy server") 14 | parser.add_argument("url", help="The backend URL to proxy to") 15 | parser.add_argument( 16 | "-p", "--port", type=int, default=8000, help="Port to use (default: 8000)" 17 | ) 18 | parser.add_argument( 19 | "--host", default="0.0.0.0", help="Host to bind to (default: 0.0.0.0)" 20 | ) 21 | parser.add_argument( 22 | "--timeout", type=float, default=None, help="Timeout in seconds" 23 | ) 24 | parser.add_argument("-v", "--verbose", action="store_true", help="Verbose logging") 25 | 26 | args = parser.parse_args() 27 | 28 | if args.verbose: 29 | import logging 30 | 31 | logging.basicConfig(level=logging.INFO) 32 | app = asgi_proxy(args.url, log=logging, timeout=args.timeout) 33 | else: 34 | app = asgi_proxy(args.url, timeout=args.timeout) 35 | 36 | uvicorn.run(app, host=args.host, port=args.port) 37 | -------------------------------------------------------------------------------- /setup.py: -------------------------------------------------------------------------------- 1 | from setuptools import setup 2 | import os 3 | 4 | VERSION = "0.2a0" 5 | 6 | 7 | def get_long_description(): 8 | with open( 9 | os.path.join(os.path.dirname(os.path.abspath(__file__)), "README.md"), 10 | encoding="utf8", 11 | ) as fp: 12 | return fp.read() 13 | 14 | 15 | setup( 16 | name="asgi-proxy-lib", 17 | description="An ASGI function for proxying to a backend over HTTP", 18 | long_description=get_long_description(), 19 | long_description_content_type="text/markdown", 20 | author="Simon Willison", 21 | url="https://github.com/simonw/asgi-proxy-lib", 22 | project_urls={ 23 | "Issues": "https://github.com/simonw/asgi-proxy-lib/issues", 24 | "CI": "https://github.com/simonw/asgi-proxy-lib/actions", 25 | "Changelog": "https://github.com/simonw/asgi-proxy-lib/releases", 26 | }, 27 | license="Apache License, Version 2.0", 28 | version=VERSION, 29 | packages=["asgi_proxy"], 30 | install_requires=["httpx"], 31 | extras_require={"test": ["pytest", "pytest-asyncio", "pytest-httpx"]}, 32 | python_requires=">=3.9", 33 | ) 34 | -------------------------------------------------------------------------------- /tests/conftest.py: -------------------------------------------------------------------------------- 1 | import pytest 2 | 3 | 4 | @pytest.fixture 5 | def assert_all_responses_were_requested() -> bool: 6 | return False 7 | 8 | 9 | @pytest.fixture 10 | def mock_backend(httpx_mock): 11 | httpx_mock.add_response(url="https://datasette.io/", text="

datasette.io

") 12 | httpx_mock.add_response(url="https://datasette.io/faq", text="FAQ goes here") 13 | httpx_mock.add_response( 14 | url="https://datasette.io/404", status_code=404, text="Not Found" 15 | ) 16 | return httpx_mock 17 | -------------------------------------------------------------------------------- /tests/test_asgi_proxy.py: -------------------------------------------------------------------------------- 1 | from asgi_proxy import asgi_proxy 2 | import httpx 3 | import pytest 4 | 5 | 6 | @pytest.mark.asyncio 7 | @pytest.mark.parametrize( 8 | "url,expected_status,expected_body", 9 | ( 10 | ( 11 | "https://datasette.io/", 12 | 200, 13 | "

datasette.io

", 14 | ), 15 | ( 16 | "https://datasette.io/faq", 17 | 200, 18 | "FAQ goes here", 19 | ), 20 | ( 21 | "https://datasette.io/404", 22 | 404, 23 | "Not Found", 24 | ), 25 | ), 26 | ) 27 | @pytest.mark.httpx_mock(assert_all_responses_were_requested=False) 28 | async def test_asgi_proxy(mock_backend, url, expected_status, expected_body): 29 | app = asgi_proxy("https://datasette.io") 30 | async with httpx.AsyncClient( 31 | transport=httpx.ASGITransport(app=app), 32 | ) as client: 33 | response = await client.get(url) 34 | assert response.status_code == expected_status 35 | assert response.text == expected_body 36 | assert len(mock_backend.get_requests()) == 1 37 | assert mock_backend.get_requests()[0].url == url 38 | 39 | 40 | @pytest.mark.asyncio 41 | @pytest.mark.httpx_mock(assert_all_responses_were_requested=False) 42 | async def test_asgi_proxy_timeout(httpx_mock): 43 | httpx_mock.add_exception(httpx.ReadTimeout("Unable to read within timeout")) 44 | app = asgi_proxy("https://datasette.io", timeout=0.1) 45 | async with httpx.AsyncClient( 46 | transport=httpx.ASGITransport(app=app), 47 | ) as client: 48 | response = await client.get("https://datasette.io/") 49 | assert response.status_code == 504 50 | assert response.text == "Gateway timeout" 51 | --------------------------------------------------------------------------------