Running a Bottle app with Gunicorn

Recently, I wrote a simple web tracker at work, using the Bottle microframework.

Looking back, maybe I should've used Flask instead, as I simply don't see the reason for stuffing 3,000 lines of code in one file, other than a proof of concept. But both frameworks are quite similar, and both have quite good documentation.

A simple bottle app looks like this:

from bottle import route, run

@route('/')
def index():
    return '<h1>Hello Bottle!</h1>'

run(host='localhost', port=8080)

To switch the server to Gunicorn replace the last line with:

run(host='localhost', port=8080, server='gunicorn', workers=4)

But what if we want to run it using the gunicorn executable (to run it with an init.d script)? Here things became more problematic.

I assumed it would be as simple as simple as running gunicorn myapp, but it was still running the app with the default server.

It also turns out that Bottle is completely not googlable, and searching for "bottle python gunicorn" just returned random crap. After about half an hour of digging, the solution turned out to be quite simple... I was missing a WSGI "app" object.

Here's the finished app:

import bottle
from bottle import route, run

@route('/')
def index():
    return '<h1>Hello Bottle!</h1>'

if __name__ == "__main__":
    run(host='localhost', port=8080)

app = bottle.default_app()

The last line sets the "app" object for the WSGI server to run.

Running the test server:

python hello_bottle.py

Running the app with Gunicorn (with 4 workers):

gunicorn -w 4 hello_bottle:app

Simple enough, but it's still a little annoying that this wasn't available in the documentation.

For comparison, in Flask, a hello world app looks like this:

from flask import Flask
app = Flask(__name__)

@app.route("/")
def hello():
    return "Hello World!"

if __name__ == "__main__":
    app.run()

The "app" object is available right away, so we don't have to guess. And the first result in Google for "flask gunicorn" is a link to the official documentation, describing how to run it with various WSGI servers.

In conclusion: Bottle was fun, the application was very easy to build, and runs incredibly fast. I think that for the next project that requires a microframework I will use Flask instead. Even if just for the sake of comparison.