Question

Scenario 1

This involves using one “gateway” route in app.yaml and then choosing the RequestHandler in the WSGIApplication.

app.yaml

- url: /.*
  script: main.py

main.py

from google.appengine.ext import webapp

class Page1(webapp.RequestHandler):
    def get(self):
        self.response.out.write("Page 1")

class Page2(webapp.RequestHandler):
    def get(self):
        self.response.out.write("Page 2")

application = webapp.WSGIApplication([
    ('/page1/', Page1),
    ('/page2/', Page2),
], debug=True)

def main():
    wsgiref.handlers.CGIHandler().run(application)

if __name__ == '__main__':
    main()

---

Scenario 2:

This involves defining two routes in app.yaml and then two separate scripts for each (page1.py and page2.py).

app.yaml

- url: /page1/
  script: page1.py
- url: /page2/
  script: page2.py

page1.py

from google.appengine.ext import webapp

class Page1(webapp.RequestHandler):
    def get(self):
        self.response.out.write("Page 1")

application = webapp.WSGIApplication([
    ('/page1/', Page1),
], debug=True)

def main():
    wsgiref.handlers.CGIHandler().run(application)

if __name__ == '__main__':
    main()

page2.py

from google.appengine.ext import webapp

class Page2(webapp.RequestHandler):
    def get(self):
        self.response.out.write("Page 2")

application = webapp.WSGIApplication([
    ('/page2/', Page2),
], debug=True)

def main():
    wsgiref.handlers.CGIHandler().run(application)

if __name__ == '__main__':
    main()

---

Question

What are the benefits and drawbacks of each pattern? Is one much faster than the other?

Answer 1

The only performance implication relates to the loading of modules: Modules are loaded on an instance when they’re first used, and splitting things up requires fewer module loads to serve a page on a new instance.

This is pretty minimal, though, as you can just as easily have the handler script dynamically load the needed module on-demand – and that’s what many common frameworks already do.

In general, app.yaml routing is designed for routing between distinct components or applications. For example, remote_api and deferred both have their own handlers. It’s perfectly reasonable, therefore, to have a single handler defined for your app that handles everything else.