now-python-asgi
A Now builder for Python ASGI applications
Quickstart
If you have an existing WSGI app, getting this builder to work for you is a
piece of
1. Add a Now configuration
Add a now.json
file to the root of your application:
{
"version": 2,
"name": "python-asgi-app",
"builds": [{
"src": "index.py",
"use": "@gbozee/now-python-asgi",
"config": { "maxLambdaSize": "15mb" }
}]
}
NB: For ASGI2 support, Use @gbozee/now-python-asgi@1.0.4
This configuration is doing a few things in the "builds"
part:
-
"src": "index.py"
This tells Now that there is one entrypoint to build for.index.py
is a file we'll create shortly. -
"use": "@ardent-labs/now-python-wsgi"
Tell Now to use this builder when deploying your application -
"config": { "maxLambdaSize": "15mb" }
Bump up the maximum size of the built application to accommodate some larger python WSGI libraries (like Django or Flask). This may not be necessary for you.
2. Add a Now entrypoint
Add index.py
to the root of your application. This entrypoint should make
available an object named application
that is an instance of your WSGI
application. E.g.:
# For a sample Starlette app
from starlette.applications import Starlette
from starlette.responses import JSONResponse
application = Starlette()
@application.route('/')
async def homepage(request):
return JSONResponse({'hello': 'world'})
# Replace `django_app` with the appropriate name to point towards your project's
# wsgi.py file
If the ASGI instance isn't named application
you can set the
wsgiApplicationName
configuration option to match your application's name (see
the configuration section below).
3. Deploy!
That's it, you're ready to go:
$ now
> Deploying python-asgi-app
...
> Success! Deployment ready [57s]
Requirements
Your project may optionally include a requirements.txt
file to declare any
dependencies.
Configuration options
runtime
Select the lambda runtime. Defaults to python3.7
.
{
"builds": [{
"config": { "runtime": "python3.7" }
}]
}
wsgiApplicationName
Select the WSGI application to run from your entrypoint. Defaults to
application
.
{
"builds": [{
"config": { "asgiApplicationName": "application" }
}]
}
Additional considerations
Routing
You'll likely want all requests arriving at your deployment url to be routed to your application. You can do this by adding a route rewrite to the Now configuration:
{
"version": 2,
"name": "python-asgi-app",
"builds": [{
"src": "index.py",
"use": "@gbozee/now-python-asgi"
}],
"routes" : [{
"src" : "/(.*)", "dest":"/"
}]
}
index.py
file
Avoiding the If having an extra file in your project is troublesome or seems unecessary, it's
also possible to configure Now to use your application directly, without passing
it through index.py
.
If your WSGI application lives in now_app/wsgi.py
and is named application
,
then you can configure it as the entrypoint and adjust routes accordingly:
{
"version": 2,
"name": "python-asgi-app",
"builds": [{
"src": "now_app/asgi.py",
"use": "@gbozee/now-python-asgi"
}],
"routes" : [{
"src" : "/(.*)", "dest":"/now_app/asgi.py"
}]
}
Lambda environment limitations
At the time of writing, Zeit Now runs on AWS Lambda. This has a number of implications on what libaries will be available to you, notably:
- PostgreSQL, so psycopg2 won't work out of the box
- MySQL, so MySQL adapters won't work out of the box either
Contributing
To-dos
- [ ] Add tests for various types of requests
Attribution
This implementation draws upon work from:
- @erm on mangum
- @ardent-co on now-python-wsgi