tornskel

  _________
  \_______
    _____/    tornskel - Tornado Skeleton
    \___      fully functional skeletal template app for a tornado web app
      _/
      \

LICENSE

This falls under the same license as TornadoWeb, the Apache License, Version 2.0 Get a copy at http://www.apache.org/licenses/LICENSE-2.0.html

GETTING STARTED

You'll need to create a settings_dev.py or settings_prod.py in order to run tornskel. The easiest way to do this is to copy settings_dev.py.template to settings_dev.py.

cp settings_dev.py.template settings_dev.py

Once you have your local settings created, check out the options to launch.py as follows.

./launch.py -h
Usage: launch.py [options]

Options:
  -h, --help            show this help message and exit
  -r, --routes          print list of routes
  -p PORT, --port=PORT  specify httpd port

If you just execute ./launch.py, a Tornado instance will be running at the port specified under port in settings.py or settings_dev.py if you edited that.

Additional Notes

Tornskel adds a few helpers beyond the standard Tornado instance, but all of these live in user space and can exist in your standard project library with no patching of Tornado needed.

Handler Routing

Tornado's default way of routing URLs to handlers is by passing a large list to the tornado app instance when it's created. This is ok if you have a few handlers, but can get a little unwieldy after a while. Also, it just feels odd to us to have to add a handler in one place, then go elsewhere to actually activate the handler.

To ease that, tornskel offers a @route(..) decorator for handlers. If your handlers extend tornskel.views.viewlib.BaseHandler, you can use this route decorator anytime you create a handler.

An example below will make this clear.

@route('/some/path')
class SomeRequestHandler(RequestHandler):
    pass

Then, when instantiating your tornado app, you can just pass in route.get_routes() where tornado wants the url routes and it will provide the urls and handlers list that tornado expects. In tornskel, we generate this route list as a member of the tornskel.tornapp.views module called routes. In tornskel/tornapp/app.py, we hand this member to our tornado.web.Application(..) instantiation call, just like you would with any other tornado app. The difference is that our routes are built at startup dynamically instead of being defined statically.

You can see this list at any time by running launch.py with the --routes option.

./launch.py --routes
    /      => tornapp.views.IndexHandler
    /yield => tornapp.views.YieldExampleHandler

Note: The order of routes appearing here is very important, as the first one encountered that matches will be the one that tornado uses. For this reason, when you import the views into your project is how you affect this list.

If you don't want to use the @route(...) decorator, just write your views and app in the standard tornado way and pretend the decorator doesn't exist. Everything will still work just fine.

Yielded Asynchronous Calls

Part of the reason that tornado is so fast is that performing asynchronous calls is very easy to incorporate with tornado's ioloop. Unfortunately, this can lead to a leapfrog approach to your handlers. Typically, you call asynchronously, and give it a function pointer to a callback. This means you need to save the state of the existing function somewhere, usually self, and then pick that back up again in the callback function. Performing iterations with multiple callbacks can be a bit tricky as you end up hopping between callbacks. We have a solution for this.

If you decorate a request handler method with @async_yield, when you make an async call, you can use python's yield to yield execution to that call until it returns. This is a bit of a break from the standard way of thinking about python's yield, but seems to work quite well. You get the ease of developing typical, serial, blocking code, but with the speed of async calls.

An example should help.

class MyHandler(BaseHandler):
    @async_yield
    def get(self):
        ... stuff ...
        yield AsyncHTTPClient().fetch(
            'http://example.com/',
            callback=self.yield_cb  # always use this
            )
        print "stuff returned is in", results

You can use tornskel without this feature, it's just there if you'd like it. To read more on this, see the source for tornskel/tornapp/views/viewlib.py and pay close attention to the comments in async_yield(...).