dynoscale 1.2.2

A simple yet efficient scaling agent for Python apps on Heroku

Dynoscale Agent

Simple yet efficient scaling agent for Python apps on Heroku

Dynoscale Agent supports both WSGI and ASGI based apps and RQ workers (DjangoQ and Celery support is coming soon). The easies way to use it in your project is import the included Gunicorn hook in your gunicorn.conf.py but we'll explain the setup process in more detail below.

Note that for auto-scaling to work, your web/workers have to run on Standard or Performace dynos!

Getting started

There are generally 3 steps to set up autoscaling with Dynoscale:

1. Add Dynoscale addon to your Heroku app
2. Install dynoscale package
3. Initialize dynoscale when you app starts

1) Enabling Dynoscale add-on

There are two ways to add the Dynoscale add-on to your app.
First one is to add the add-on through the Heroku dashboard by navigating to your app, then selecting the resources tab and finally searching for dynoscale then select your plan and at this point your app will be restarted with the addon enabled.

The second option is to install it with heroku cli tools, using this command for example:

heroku addons:create dscale:performance

2) Installing dynoscale agent package

This is same as installing any other Python package, for example: python -m pip install dynoscale.

If you'd like to confirm it's installed by heroku, then run:

heroku run python -c "import dynoscale; print(dynoscale.__version__)"  

which will print out the installed version (for example: 1.2.0)

If you'd like to confirm that dynoscale found the right env vars run:

heroku run python -c "from dynoscale.config import Config; print(Config())"

and you'll likely see something like this:

Running python -c "from dynoscale.config import Config; print(Config())" on ⬢ your-app-name-here... up, run.9816 (Eco)
{"DYNO": "run.9816", "DYNOSCALE_DEV_MODE": false, "DYNOSCALE_URL": "https://dynoscale.net/api/v1/report/yoursecretdynoscalehash", "redis_urls": {"REDISCLOUD_URL": "redis://default:[e-mail]:12345"}}

3) Initialize dynoscale during the app startup

This can take multiple forms and depends on your app. Is your app WSGI or ASGI? How do you serve it? Do you have workers? There are examples in the repo, take a look! I hope you'll find something close to your setup.

If you have a WSGI app (ex.: Bottle, Flask, CherryPy, Pylons, Django, ...) and you serve the app with Gunicorn then in your gunicorn.conf.py just import the pre_request hook from dynoscale and that's it:

# `gunicorn.conf.py` - Using Dynoscale Gunicorn Hook
from dynoscale.hooks.gunicorn import pre_request  # noqa # pylint: disable=unused-import

Or if you prefer you can instead pass your WSGI app into DynoscaleWsgiApp():

# `web.py` - Flask Example
from dynoscale.wsgi import DynoscaleWsgiApp

app = Flask(__name__)
app.wsgi_app = DynoscaleWsgiApp(app.wsgi_app)

Do you use Gunicorn with Uvicorn workers? Replace uvicorn.workers.UvicornWorker with dynoscale.DynoscaleUvicornWorker like so:

# Contents of gunicorn.conf.py
...
# worker_class = 'uvicorn.workers.UvicornWorker'
worker_class = 'dynoscale.uvicorn.DynoscaleUvicornWorker'
...

... and you're done!

Do you serve you ASGI app some other way? (ex.: Starlette, Responder, FastAPI, Sanic, Django, Guillotina, ...)_ wrap your ASGI app with DynoscaleASGIApp:

# `web.py` - Starlette Example
import os

from starlette.applications import Starlette
from starlette.responses import Response
from starlette.routing import Route

from dynoscale.asgi import DynoscaleAsgiApp


async def home(_):
    return Response("Hello from Starlette, scaled by Dynoscale!", media_type='text/plain')


app = DynoscaleAsgiApp(Starlette(debug=True, routes=[Route('/', endpoint=home, methods=['GET'])]))

if __name__ == "__main__":
    import uvicorn

    uvicorn.run('web:app', host='0.0.0.0', port=int(os.getenv('PORT', '8000')), log_level="info")

---

📖 Complete WSGI example

1. Add dynoscale to your app on Heroku: heroku addons:create dscale
2. Install dynoscale: python -m pip install dynoscale
   1. Add dynoscale to your app, you can either wrap your app or if you use Gunicorn, you can also just use one of its hooks (pre_request):
      1. If you want to wrap you app (let's look at Flask example):

      import os
      
      from flask import Flask
      
      app = Flask(__name__)
      
      @app.route("/")
      def index():
          return "Hello from Flask!"
      
      if __name__ == "__main__":
          app.run(host='0.0.0.0', port=int(os.getenv('PORT', '8000')), debug=True)
      

      then just wrap your WSGI app like this

      from flask import Flask
      # FIRST, IMPORT DYNOSCALE
      from dynoscale.wsgi import DynoscaleWsgiApp
      
      app = Flask(__name__)
      
      @app.route("/")
      def index():
          return "Hello from Flask!"
      
      if __name__ == "__main__":
          # THE CHANGE BELOW IS ALL YOU NEED TO DO
          app.wsgi_app = DynoscaleWsgiApp(app.wsgi_app)
          # YUP, WE KNOW, CAN'T GET SIMPLER THAN THAT :)
          app.run(host='127.0.0.1', port=3000, debug=True)
      

   2. Or, if you'd prefer to use the hook, then change your gunicorn.conf.py accordingly instead:

      # This one line will do it for you:
      from dynoscale.hooks.gunicorn import pre_request  # noqa # pylint: disable=unused-import
      

      If you already use the pre_request hook, alias ours and call it manually:

      # Alias the import...
      from dynoscale.hooks.gunicorn import pre_request as hook
      
      # ...and remember to call ours first!
      def pre_request(worker, req):
         hook(worker, req)
         # ...do your own thing...
      

3. Profit! Literally, this will save you money! 💰💰💰 😏

📖 Complete ASGI example

1. Add dynoscale to your app on Heroku: heroku addons:create dscale
2. Prepare your amazing webapp, we'll use Starlette served by Gunicorn with Uvicorn workers:

   # web.py
   import datetime
   from starlette.applications import Starlette
   from starlette.responses import Response
   from starlette.routing import Route
   
   
   async def home(_):
       return Response(
           "Hello from 🌟 Starlette 🌟 served by Gunicorn using Uvicorn workers and scaled by Dynoscale!\n"
           f"It's {datetime.datetime.now()} right now.",
           media_type='text/plain'
       )
   
   
   app = Starlette(debug=True, routes=[Route('/', endpoint=home, methods=['GET'])])
   

   ... add Gunicorn config:

   # gunicorn.conf.py
   import os
   # ENV vars
   PORT = int(os.getenv('PORT', '3000'))
   WEB_CONCURRENCY = int(os.getenv('WEB_CONCURRENCY', '10'))
   
   # Gunicorn config
   wsgi_app = "web:app"
   
   # ┌---------- THIS HERE IS ALL OF DYNOSCALE SETUP ----------┐
   # | # worker_class = 'uvicorn.workers.UvicornWorker'        |
   worker_class = 'dynoscale.uvicorn.DynoscaleUvicornWorker' # |
   # └---------------------------------------------------------┘
   
   bind = f"0.0.0.0:{PORT}"
   preload_app = True
   
   workers = WEB_CONCURRENCY
   max_requests = 1000
   max_requests_jitter = 50
   
   accesslog = '-'
   loglevel = 'debug'
   

3. Install all the dependencies:
   • python -m pip install "uvicorn[standard]" gunicorn dynoscale
4. Start it up with:

     DYNO=web.1 DYNOSCALE_DEV_MODE=true DYNOSCALE_URL=https://some_request_bin_or_some_such.com gunicorn
   

   • On Heroku, DYNO and DYNOSCALE_URL will be set for you, you should only have web: gunicorn in your procfile.
   • In this example we start Dynoscale in dev mode to simulate random queue times, don't do this on Heroku!
5. That's it you're done, now Profit! Literally, this will save you money! 💰💰💰 😏

ℹ️ Info

You should consider the dynoscale.wsgi.DynoscaleWsgiApp(wsgi_app), dynoscale.hooks.gunicorn.pre_request(worker, req), dynoscale.asgi.DynoscaleASGIApp(asgi_app) and dynoscale.uvicorn.DynoscaleUvicornWorker the only parts of the public interface.

🤯 Examples

Please check out ./examples, yes, we do have examples in the repository :)

👩‍💻 Contributing

Install development requirements:

• pip install -e ".[test]"

You can run pytest from terminal: pytest

You can run flake8 from terminal: flake8 ./src

Changelog of dynoscale for Python

1.2.2 [TBD]

• updated test/dev dependencies
• adding support for TLS redis urls with self-signed certificates

1.2.1 [2023-03-01]

• Fix: Limit resource consumption while reporting on extreme numbers of pending tasks.

1.2.0 [2023-01-08]

• dropping support for Python 3.7, 3.8, 3.9
• adding support for Gunicorn with Uvicorn workers, use dynoscale.uvicorn.DynoscaleUnicornWorker

1.1.3 [2023-01-13]

• Added support for ASGI through DynoscaleAsgiApp class
• Added options to control DS repository storage location with environment variables

1.1.2 [2022-05-27]

• Added logging to DynoscaleRQLogger

1.1.1 [2022-05-12]

• fixed issue when using GUNICORN hook (Incorrect key name in headers)

1.1.0 [2022-03-25]

• Support for RQ

1.0.0 [2022-02-27]

First public release