Advanced¶
For the following scenarios, you might prefer fastapi_proxy_lib.core:
- When you need to use proxies with only
Starlettedependencies (withoutFastAPI). - When you need more fine-grained control over parameters and lifespan event.
- When you need to further process the input and output before and after the proxy (similar to middleware).
We will demonstrate with FastAPI,
but you can completely switch to the Starlette approach,
which is officially supported by this project.
Starlette Support¶
Please visit the ReverseHttpProxy#examples to view the demo with annotations .
Also (without annotations):
Modify request¶
In some cases, you may want to make final modifications before sending a request, such as performing behind-the-scenes authentication by modifying the headers of request.
httpx provides comprehensive authentication support, and fastapi-proxy-lib offers first-class support for httpx.
See https://www.python-httpx.org/advanced/#customizing-authentication
You can refer following example to implement a simple authentication:
from collections.abc import Generator
from typing import Any
import httpx
from fastapi_proxy_lib.fastapi.app import reverse_http_app
from httpx import Request
class MyCustomAuth(httpx.Auth):
# ref: https://www.python-httpx.org/advanced/#customizing-authentication
def __init__(self, token: str):
self.token = token
def auth_flow(self, request: httpx.Request) -> Generator[Request, Any, None]:
# Send the request, with a custom `X-Authentication` header.
request.headers["X-Authentication"] = self.token
yield request
app = reverse_http_app(
client=httpx.AsyncClient(auth=MyCustomAuth("bearer_token")),
base_url="http://www.httpbin.org/",
)
visit /headers to see the result which contains "X-Authentication": "bearer_token" header.
Modify response¶
In some cases, you may want to make final modifications before return the response to the client, such as transcoding video response streams.
See issue#15
You can refer following example to modify the response:
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager
from fastapi import FastAPI
from fastapi_proxy_lib.core.http import ReverseHttpProxy
from starlette.requests import Request
from starlette.responses import AsyncContentStream, StreamingResponse
proxy = ReverseHttpProxy(base_url="http://www.example.com/")
@asynccontextmanager
async def close_proxy_event(_: FastAPI) -> AsyncIterator[None]:
"""Close proxy."""
yield
await proxy.aclose()
app = FastAPI(lifespan=close_proxy_event)
async def new_content(origin_content: AsyncContentStream) -> AsyncContentStream:
"""Fake content processing."""
async for chunk in origin_content:
# do some processing with chunk, e.g transcoding,
# here we just print and return it as an example.
print(chunk)
yield chunk
@app.get("/{path:path}")
async def _(request: Request, path: str = ""):
proxy_response = await proxy.proxy(request=request, path=path)
if isinstance(proxy_response, StreamingResponse):
# get the origin content stream
old_content = proxy_response.body_iterator
new_resp = StreamingResponse(
content=new_content(old_content),
status_code=proxy_response.status_code,
headers=proxy_response.headers,
media_type=proxy_response.media_type,
)
return new_resp
return proxy_response
visit /, you will notice that the response body is printed to the console.
Modify (redefine) response only to particular endpoint¶
from collections.abc import AsyncIterator
from contextlib import asynccontextmanager
from fastapi import FastAPI
from fastapi_proxy_lib.core.http import ReverseHttpProxy
from starlette.requests import Request
proxy = ReverseHttpProxy(base_url="http://httpbin.org/")
@asynccontextmanager
async def close_proxy_event(_: FastAPI) -> AsyncIterator[None]:
"""Close proxy."""
yield
await proxy.aclose()
app = FastAPI(lifespan=close_proxy_event)
@app.get("/{path:path}")
@app.post("/{path:path}")
async def _(request: Request, path: str = ""):
if path == "ip" and request.method == "GET":
return {"msg": "Method is redefined"}
else:
return await proxy.proxy(request=request, path=path)
In this example all requests except GET /ip will be passed to httpbin.org: