├── .gitignore
├── tests
├── conftest.py
└── test_asgi_proxy.py
├── .github
└── workflows
│ ├── test.yml
│ └── publish.yml
├── setup.py
├── asgi_proxy
├── __main__.py
└── __init__.py
├── README.md
└── LICENSE
/.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 |
--------------------------------------------------------------------------------
/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 |
--------------------------------------------------------------------------------
/.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 |
--------------------------------------------------------------------------------
/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 |
--------------------------------------------------------------------------------
/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 |
--------------------------------------------------------------------------------
/.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 |
--------------------------------------------------------------------------------
/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 |
--------------------------------------------------------------------------------
/README.md:
--------------------------------------------------------------------------------
1 | # asgi-proxy-lib
2 |
3 | [](https://pypi.org/project/asgi-proxy-lib/)
4 | [](https://github.com/simonw/asgi-proxy-lib/releases)
5 | [](https://github.com/simonw/asgi-proxy-lib/blob/main/LICENSE)
6 |
7 | An ASGI function for proxying to a backend over HTTP
8 |
9 | **⚠️ Warning: this is an early alpha.**
10 |
11 | ## Installation
12 |
13 | Install this library using `pip`:
14 |
15 | pip install asgi-proxy-lib
16 |
17 | ## Usage
18 |
19 | This library provides a single ASGI function called `asgi_proxy`. 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 |
--------------------------------------------------------------------------------
/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. Definitions.
8 |
9 | "License" shall mean the terms and conditions for use, reproduction,
10 | and distribution as defined by Sections 1 through 9 of this document.
11 |
12 | "Licensor" shall mean the copyright owner or entity authorized by
13 | the copyright owner that is granting the License.
14 |
15 | "Legal Entity" shall mean the union of the acting entity and all
16 | other entities that control, are controlled by, or are under common
17 | control with that entity. For the purposes of this definition,
18 | "control" means (i) the power, direct or indirect, to cause the
19 | direction or management of such entity, whether by contract or
20 | otherwise, or (ii) ownership of fifty percent (50%) or more of the
21 | outstanding shares, or (iii) beneficial ownership of such entity.
22 |
23 | "You" (or "Your") shall mean an individual or Legal Entity
24 | exercising permissions granted by this License.
25 |
26 | "Source" form shall mean the preferred form for making modifications,
27 | including but not limited to software source code, documentation
28 | source, and configuration files.
29 |
30 | "Object" form shall mean any form resulting from mechanical
31 | transformation or translation of a Source form, including but
32 | not limited to compiled object code, generated documentation,
33 | and conversions to other media types.
34 |
35 | "Work" shall mean the work of authorship, whether in Source or
36 | Object form, made available under the License, as indicated by a
37 | copyright notice that is included in or attached to the work
38 | (an example is provided in the Appendix below).
39 |
40 | "Derivative Works" shall mean any work, whether in Source or Object
41 | form, that is based on (or derived from) the Work and for which the
42 | editorial revisions, annotations, elaborations, or other modifications
43 | represent, as a whole, an original work of authorship. For the purposes
44 | of this License, Derivative Works shall not include works that remain
45 | separable from, or merely link (or bind by name) to the interfaces of,
46 | the Work and Derivative Works thereof.
47 |
48 | "Contribution" shall mean any work of authorship, including
49 | the original version of the Work and any modifications or additions
50 | to that Work or Derivative Works thereof, that is intentionally
51 | submitted to Licensor for inclusion in the Work by the copyright owner
52 | or by an individual or Legal Entity authorized to submit on behalf of
53 | the copyright owner. For the purposes of this definition, "submitted"
54 | means any form of electronic, verbal, or written communication sent
55 | to the Licensor or its representatives, including but not limited to
56 | communication on electronic mailing lists, source code control systems,
57 | and issue tracking systems that are managed by, or on behalf of, the
58 | Licensor for the purpose of discussing and improving the Work, but
59 | excluding communication that is conspicuously marked or otherwise
60 | designated in writing by the copyright owner as "Not a Contribution."
61 |
62 | "Contributor" shall mean Licensor and any individual or Legal Entity
63 | on behalf of whom a Contribution has been received by Licensor and
64 | subsequently incorporated within the Work.
65 |
66 | 2. Grant of Copyright License. Subject to the terms and conditions of
67 | this License, each Contributor hereby grants to You a perpetual,
68 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable
69 | copyright license to reproduce, prepare Derivative Works of,
70 | publicly display, publicly perform, sublicense, and distribute the
71 | Work and such Derivative Works in Source or Object form.
72 |
73 | 3. Grant of Patent License. Subject to the terms and conditions of
74 | this License, each Contributor hereby grants to You a perpetual,
75 | worldwide, non-exclusive, no-charge, royalty-free, irrevocable
76 | (except as stated in this section) patent license to make, have made,
77 | use, offer to sell, sell, import, and otherwise transfer the Work,
78 | where such license applies only to those patent claims licensable
79 | by such Contributor that are necessarily infringed by their
80 | Contribution(s) alone or by combination of their Contribution(s)
81 | with the Work to which such Contribution(s) was submitted. If You
82 | institute patent litigation against any entity (including a
83 | cross-claim or counterclaim in a lawsuit) alleging that the Work
84 | or a Contribution incorporated within the Work constitutes direct
85 | or contributory patent infringement, then any patent licenses
86 | granted to You under this License for that Work shall terminate
87 | as of the date such litigation is filed.
88 |
89 | 4. Redistribution. You may reproduce and distribute copies of the
90 | Work or Derivative Works thereof in any medium, with or without
91 | modifications, and in Source or Object form, provided that You
92 | meet the following conditions:
93 |
94 | (a) You must give any other recipients of the Work or
95 | Derivative Works a copy of this License; and
96 |
97 | (b) You must cause any modified files to carry prominent notices
98 | stating that You changed the files; and
99 |
100 | (c) You must retain, in the Source form of any Derivative Works
101 | that You distribute, all copyright, patent, trademark, and
102 | attribution notices from the Source form of the Work,
103 | excluding those notices that do not pertain to any part of
104 | the Derivative Works; and
105 |
106 | (d) If the Work includes a "NOTICE" text file as part of its
107 | distribution, then any Derivative Works that You distribute must
108 | include a readable copy of the attribution notices contained
109 | within such NOTICE file, excluding those notices that do not
110 | pertain to any part of the Derivative Works, in at least one
111 | of the following places: within a NOTICE text file distributed
112 | as part of the Derivative Works; within the Source form or
113 | documentation, if provided along with the Derivative Works; or,
114 | within a display generated by the Derivative Works, if and
115 | wherever such third-party notices normally appear. The contents
116 | of the NOTICE file are for informational purposes only and
117 | do not modify the License. You may add Your own attribution
118 | notices within Derivative Works that You distribute, alongside
119 | or as an addendum to the NOTICE text from the Work, provided
120 | that such additional attribution notices cannot be construed
121 | as modifying the License.
122 |
123 | You may add Your own copyright statement to Your modifications and
124 | may provide additional or different license terms and conditions
125 | for use, reproduction, or distribution of Your modifications, or
126 | for any such Derivative Works as a whole, provided Your use,
127 | reproduction, and distribution of the Work otherwise complies with
128 | the conditions stated in this License.
129 |
130 | 5. Submission of Contributions. Unless You explicitly state otherwise,
131 | any Contribution intentionally submitted for inclusion in the Work
132 | by You to the Licensor shall be under the terms and conditions of
133 | this License, without any additional terms or conditions.
134 | Notwithstanding the above, nothing herein shall supersede or modify
135 | the terms of any separate license agreement you may have executed
136 | with Licensor regarding such Contributions.
137 |
138 | 6. Trademarks. This License does not grant permission to use the trade
139 | names, trademarks, service marks, or product names of the Licensor,
140 | except as required for reasonable and customary use in describing the
141 | origin of the Work and reproducing the content of the NOTICE file.
142 |
143 | 7. Disclaimer of Warranty. Unless required by applicable law or
144 | agreed to in writing, Licensor provides the Work (and each
145 | Contributor provides its Contributions) on an "AS IS" BASIS,
146 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
147 | implied, including, without limitation, any warranties or conditions
148 | of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
149 | PARTICULAR PURPOSE. You are solely responsible for determining the
150 | appropriateness of using or redistributing the Work and assume any
151 | risks associated with Your exercise of permissions under this License.
152 |
153 | 8. Limitation of Liability. In no event and under no legal theory,
154 | whether in tort (including negligence), contract, or otherwise,
155 | unless required by applicable law (such as deliberate and grossly
156 | negligent acts) or agreed to in writing, shall any Contributor be
157 | liable to You for damages, including any direct, indirect, special,
158 | incidental, or consequential damages of any character arising as a
159 | result of this License or out of the use or inability to use the
160 | Work (including but not limited to damages for loss of goodwill,
161 | work stoppage, computer failure or malfunction, or any and all
162 | other commercial damages or losses), even if such Contributor
163 | has been advised of the possibility of such damages.
164 |
165 | 9. Accepting Warranty or Additional Liability. While redistributing
166 | the Work or Derivative Works thereof, You may choose to offer,
167 | and charge a fee for, acceptance of support, warranty, indemnity,
168 | or other liability obligations and/or rights consistent with this
169 | License. However, in accepting such obligations, You may act only
170 | on Your own behalf and on Your sole responsibility, not on behalf
171 | of any other Contributor, and only if You agree to indemnify,
172 | defend, and hold each Contributor harmless for any liability
173 | incurred by, or claims asserted against, such Contributor by reason
174 | of your accepting any such warranty or additional liability.
175 |
176 | END OF TERMS AND CONDITIONS
177 |
178 | APPENDIX: How to apply the Apache License to your work.
179 |
180 | To apply the Apache License to your work, attach the following
181 | boilerplate notice, with the fields enclosed by brackets "[]"
182 | replaced with your own identifying information. (Don't include
183 | the brackets!) The text should be enclosed in the appropriate
184 | comment syntax for the file format. We also recommend that a
185 | file or class name and description of purpose be included on the
186 | same "printed page" as the copyright notice for easier
187 | identification within third-party archives.
188 |
189 | Copyright [yyyy] [name of copyright owner]
190 |
191 | Licensed under the Apache License, Version 2.0 (the "License");
192 | you may not use this file except in compliance with the License.
193 | You may obtain a copy of the License at
194 |
195 | http://www.apache.org/licenses/LICENSE-2.0
196 |
197 | Unless required by applicable law or agreed to in writing, software
198 | distributed under the License is distributed on an "AS IS" BASIS,
199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
200 | See the License for the specific language governing permissions and
201 | limitations under the License.
202 |
--------------------------------------------------------------------------------