Google App Engine ¶

Introduction

This howto will show you how to use a PyAMF application (0.3.1 or newer) with Google App Engine.

Google App Engine (GAE) lets you run your web applications on Google’s infrastructure for free. You can serve your app using a free domain name on the appspot.com domain, or use Google Apps to serve it from your own domain.

GAE applications are implemented using Python 2.5.2. The runtime environment includes the full Python language and most of the Python standard library, including Django.

Contents

Google App Engine

Prerequisites ¶

Before you can start using GAE you need to download and install:

Python 2.5 or newer for your platform from the Python website. Users of Mac OS X 10.5 or newer already have Python 2.5 or newer installed.
Google App Engine SDK
PyAMF 0.3.1 or newer

Create Project ¶

Start a new GAE project:

Create a new folder for your project
Copy main.py, app.yaml, and index.yaml from google_appengine/new_project_template to your new folder. On a Mac you can find it under /usr/local
Move the pyamf folder from your unpacked PyAMF-0.x.x folder to the root folder of the new GAE project

Using a terminal the steps above would translate into something like:

cp -R /usr/local/google_appengine/new_project_template MyProject
cp -R PyAMF-0.5.1/pyamf MyProject
cd MyProject
ls -l

The folder structure of your project should look something like this:

+ MyProject
  - app.yaml
  - index.yaml
  - main.py
  - pyamf

Application ¶

You can setup your application using the WebAppGateway or the WSGIGateway.

WebApp Gateway ¶

The pyamf.remoting.gateway.google.WebAppGateway class allows a GAE application to handle AMF requests on the root URL and other standard HTTP requests on another URL (/helloworld in the examples below).

The main.py module tells GAE what code to launch. Modify it for PyAMF:

import logging

from google.appengine.ext import webapp
from google.appengine.ext.webapp.util import run_wsgi_app

from pyamf.remoting.gateway.google import WebAppGateway


class MainPage(webapp.RequestHandler):
    def get(self):
        self.response.headers['Content-Type'] = 'text/plain'
        self.response.out.write('Hello, webapp World!')


def echo(data):
    return data


def main():
    debug_enabled = True

    services = {
        'myservice.echo': echo,
    }

    gateway = WebAppGateway(services, logger=logging, debug=debug_enabled)

    application_paths = [('/', gateway), ('/helloworld', MainPage)]
    application = webapp.WSGIApplication(application_paths, debug=debug_enabled)

    run_wsgi_app(application)


if __name__ == '__main__':
  main()

WSGI Gateway ¶

If you don’t want to use the pure google.appengine approach as described above, you can also use pyamf.remoting.gateway.wsgi.WSGIGateway by modifying your main.py like this:

import logging
import wsgiref.handlers

from pyamf.remoting.gateway.wsgi import WSGIGateway


def echo(data):
    return data


def main():
    services = {
        'myservice.echo': echo,
    }

    gateway = WSGIGateway(services, logger=logging, debug=True)
    wsgiref.handlers.CGIHandler().run(gateway)


if __name__ == '__main__':
    main()

Start the server ¶

Run this command from your application folder:

/usr/local/google_appengine/dev_appserver.py --debug --address=localhost --port=8080 .

Once the server started it usually prints something like:

INFO     2010-03-10 00:06:22,840 dev_appserver_main.py:399] Running application new-project-template on port 8080: http://localhost:8080

Test the application ¶

When you visit http://localhost:8080/helloworld in your browser it should show a simple message:

Hello, webapp World!

The AMF gateway is available on http://localhost:8080, so this should return a 405 in the browser:

405 Method Not Allowed

To access this PyAMF gateway you must use POST requests (GET received)

Python ¶

To test the gateway you can use a Python AMF client like this:

import logging

from pyamf.remoting.client import RemotingService

	
logging.basicConfig(
    level=logging.DEBUG,
    format='%(asctime)s %(levelname)-5.5s [%(name)s] %(message)s'
)


path = 'http://localhost:8080/'
gw = RemotingService(path, logger=logging, debug=True)
service = gw.getService('myservice')

print service.echo('Hello World!')

Flash ¶

Create a new Adobe Flash document and place a TextField on the stage. Make it dynamic in the Properties pane, and give it the instance name output. Then, paste the following code into the Actions pane:

import flash.net.*;

var netConnection:NetConnection = new NetConnection();
netConnection.connect("http://localhost:8080/");

var responder:Responder = new Responder(onComplete, onFail);
netConnection.call("myservice.echo", responder, "Flash talked to PyAMF.  They both say hello.");

function onComplete(results)
{
        output.htmlText = results;
}

function onFail(results)
{
        for each (var thisResult in results)
        {
                output.text += thisResult;
        }
}

Run Debug > Debug movie to test PyAMF with Google App Engine! Other examples for Flex etc can be found on the Examples page.

Useful Resources ¶

http://aralbalkan.com/1307: Aral Balkan - Building Flash applications with Google App Engine.
Django: PyAMF integration with Django.
ByteArray: ByteArray example using Django and Flex.
http://blog.pyamf.org/archives/pyamf-and-google-app-engine: Related post on PyAMF blog.
http://pyamf.appspot.com/punit: Run the PyAMF test suite on the Google App Engine.