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https://github.com/steinitzu/fastapi-etag
Convenience library for working with etags in fastapi
https://github.com/steinitzu/fastapi-etag
asyncio caching etag fastapi http-cache
Last synced: 4 months ago
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Convenience library for working with etags in fastapi
- Host: GitHub
- URL: https://github.com/steinitzu/fastapi-etag
- Owner: steinitzu
- License: mit
- Created: 2019-12-30T22:16:06.000Z (about 5 years ago)
- Default Branch: master
- Last Pushed: 2022-05-16T20:12:08.000Z (over 2 years ago)
- Last Synced: 2024-09-29T02:21:44.716Z (4 months ago)
- Topics: asyncio, caching, etag, fastapi, http-cache
- Language: Python
- Size: 85.9 KB
- Stars: 25
- Watchers: 4
- Forks: 6
- Open Issues: 5
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
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README
# fastapi-etag
## Quickstart
Basic etag support for FastAPI, allowing you to benefit from conditional caching in web browsers and reverse-proxy caching layers.
This does not generate etags that are a hash of the response content, but instead lets you pass in a custom etag generating function per endpoint that is called before executing the route function.
This lets you bypass expensive API calls when client includes a matching etag in the `If-None-Match` header, in this case your endpoint is never called, instead returning a 304 response telling the client nothing has changed.
The etag logis is implemented with a fastapi dependency that you can add to your routes or entire routers.
Here's how you use it:
```python3
# app.py
from fastapi import FastAPI
from starlette.requests import Request
from fastapi_etag import Etag, add_exception_handler
app = FastAPI()
add_exception_handler(app)
async def get_hello_etag(request: Request):
return "etagfor" + request.path_params["name"]
@app.get("/hello/{name}", dependencies=[Depends(Etag(get_hello_etag))])
async def hello(name: str):
return {"hello": name}
```
Run this example with `uvicorn: uvicorn --port 8090 app:app`
Let's break it down:
```python3
add_exception_handler(app)
```
The dependency raises a special `CacheHit` exception to exit early when there's a an etag match, this adds a standard exception handler to the app to generate a correct 304 response from the exception.
```python3
async def get_hello_etag(request: Request):
name = request.path_params.get("name")
return f"etagfor{name}"
```
This is the function that generates the etag for your endpoint.
It can do anything you want, it could for example return a hash of a last modified timestamp in your database.
It can be either a normal function or an async function.
Only requirement is that it accepts one argument (request) and that it returns either a string (the etag) or `None` (in which case no etag header is added)
```python3
@app.get("/hello/{name}", dependencies=[Depends(Etag(get_hello_etag))])
def hello(name: str):
...
```
The `Etag` dependency is called like any fastapi dependency.
It always adds the etag returned by your etag gen function to the response.
If client passes a matching etag in the `If-None-Match` header, it will raise a `CacheHit` exception which triggers a 304 response before calling your endpoint.
Now try it with curl:
```
curl -i "http://localhost:8090/hello/bob"
HTTP/1.1 200 OK
date: Mon, 30 Dec 2019 21:55:43 GMT
server: uvicorn
content-length: 15
content-type: application/json
etag: W/"etagforbob"
{"hello":"bob"}
```
Etag header is added
Now including the etag in `If-None-Match` header (mimicking a web browser):
```
curl -i -X GET "http://localhost:8090/hello/bob" -H "If-None-Match: W/\"etagforbob\""
HTTP/1.1 304 Not Modified
date: Mon, 30 Dec 2019 21:57:37 GMT
server: uvicorn
etag: W/"etagforbob"
```
It now returns no content, only the 304 telling us nothing has changed.
### Add response headers
If you want to add some extra response headers to the 304 and regular response,
you can add the `extra_headers` argument with a dict of headers:
```
@app.get(
"/hello/{name}",
dependencies=[
Depends(
Etag(
get_hello_etag,
extra_headers={"Cache-Control": "public, max-age: 30"},
)
)
],
)
def hello(name: str):
...
```
This will add the `cache-control` header on all responses from the endpoint.
## Contributing
See [CONTRIBUTING.md](CONTRIBUTING.md)