Prerender Python Starlette
Starlette middleware for Prerender
Documentation: https://BeeMyDesk.github.io/prerender-python-starlette/
Source Code: https://github.com/BeeMyDesk/prerender-python-starlette
Introduction
Google, Facebook, Twitter, and Bing are constantly trying to view your website... but Google is the only crawler that executes a meaningful amount of JavaScript and Google even admits that they can execute JavaScript weeks after actually crawling. Prerender allows you to serve the full HTML of your website back to Google and other crawlers so that they don't have to execute any JavaScript. Google recommends using Prerender.io to prevent indexation issues on sites with large amounts of JavaScript.
Prerender is perfect for Angular SEO, React SEO, Vue SEO, and any other JavaScript framework.
This middleware intercepts requests to your Node.js website from crawlers, and then makes a call to the (external) Prerender Service to get the static HTML instead of the JavaScript for that page. That HTML is then returned to the crawler.
README of prerender_rails
This library is a Python implementation of a Prerender middleware for Starlette. It should work flawlessly with FastAPI and, probably, with any ASGI framework.
Installation
pip install prerender-python-starlette
Usage
from starlette.applications import Starlette
from starlette.middleware import Middleware
from prerender_python_starlette import PrerenderMiddleware
routes = ...
middleware = [
Middleware(PrerenderMiddleware),
]
app = Starlette(routes=routes, middleware=middleware)
Parameters
prerender_service_url: URL of Prerender server. Defaults toPRERENDER_SERVICE_URLenvironment variable.prerender_service_username: HTTP basic auth username of Prerender server. Defaults toPRERENDER_SERVICE_USERNAMEenvironment variable.prerender_service_password: HTTP basic auth password of Prerender server. Defaults toPRERENDER_SERVICE_PASSWORDenvironment variable.prerender_service_token: Token set inX-Prerender-Tokenheader. Defaults toPRERENDER_SERVICE_TOKENenvironment variable.crawler_user_agents: List of crawler user agents to intercept. Defaults toDEFAULT_CRAWLER_USER_AGENTSlist.extensions_to_ignore: List of file extensions to ignore. Defaults toDEFAULT_EXTENSIONS_TO_IGNORElist.whitelist: List of path patterns to whitelist. Path not matching a pattern in the list won't be prerendered. Defaults toNone.blacklist: List of path patterns to blacklist. Path matching a pattern in the list won't be prerendered. Defaults toNone.before_render: Async function called before the prerendering. If it returns anHTMLResponse, it will be considered as cache and will bypass the call to the Prerender server. Defaults toNone.after_render: Async function called after the prerendering. Defaults toNone.
Cache example
from starlette.applications import Starlette
from starlette.middleware import Middleware
from prerender_python_starlette import PrerenderMiddleware
async def before_render(request: Request) -> Optional[HTMLResponse]:
cached_response = await cache.get(f"prerender:{request.url.path}")
if cached_response:
return HTMLResponse(cached_response)
return None
async def after_render(
request: Request, response: HTMLResponse, cached: bool
) -> None:
if not cached:
await cache.set(
f"prerender:{request.url.path}", response.body.decode(response.charset)
)
routes = ...
middleware = [
Middleware(PrerenderMiddleware, before_render=before_render, after_render=after_render),
]
app = Starlette(routes=routes, middleware=middleware)
Development
Setup environement
You should have Pipenv installed. Then, you can install the dependencies with:
pipenv install --dev
After that, activate the virtual environment:
pipenv shell
Run unit tests
You can run all the tests with:
make test
Alternatively, you can run pytest yourself:
pytest
Format the code
Execute the following command to apply isort and black formatting:
make format
License
This project is licensed under the terms of the MIT license.
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