Google App Engine Rails Template

Ruby JRuby
1

Hi,
I just finished posting a rails template that creates an app ready to
deploy
on the Google App Engine. Check out the blog post
http://www.codingforrent.com/posts/8001 and the template at
http://github.com/joshsmoore/gaej_rails_template/tree/master. It is
still a
bit of work in progress. But, it should take care of the basics of
getting
a Rails app set up for deployment on the Google App Engine. Please tell
me
what you think.

Josh

2

Hi Chris,

I think that it is possible to develop ruby apps without the need to
restart
(
http://dev.massivebraingames.com/past/2009/4/15/writing_sinatra_apps_for_google/).
I will be honest I have not looked into this much. However, I think the
problem with rails is that development mode seems to be incompatible
with
App Engine (I think it has something to do with the rails app trying to
access the file system). I think if rails can be configured to not
cache
the app files it might work like it does for sinatra. I am looking into
that
now, if you have any insites please let me know.

About your last question I have personally not had any experience with
converting an existing rails app to work with App Engine. So far I have
worked completely with building new onces.

Josh

3

Hi Josh.

This is a helpful tool for creating a skeleton app. It starts from the
opposite end of the process than I have been using - creating my Rails
app
and then warbling it and making those tweaks listed in your script. But
with
your script it seems the idea is to create the app elsewhere perhaps and
then copy the Rails code into the app directory once the skeleton has
been
created with your script.

The biggest problem, which you alluded to in your blog post, still seems
to
be the need to restart the dev server between code changes. I believe
this
has to do with the fact that the Jetty server, which normally allows hot
deploy for native Java projects, does not allow hot deploy when a
scripting
language like Ruby, Groovy or Python is running on top of Java. A
potential
solution to this is to use jetty-rails. As of yet I have not figured
whether
it is possible to get it to work with an App Engine Rails project:

The other adjustment with Rails development on App Engine has to do with
the
ORM but is still related to the hot deploy problem with Jetty.
Datamapper
and Ola B.'s Bumble seem to be the best solutions at the moment. But
because of the need to restart the dev server between code changes, it
seems
to be more efficient to develop a Rails app first outside of the
Eclipse/App
Engine IDE using a real database and ORM and then later modify the app
to
work with Datamapper/Bumble. At least that’s the approach I have decided
to
take at the moment. The Eclipse/App Engine environment slows me down too
much to allow my development to proceed at a productive pace. I would be
curious whether you have discovered any useful tips for the process of
converting a regular app from ActiveRecord+Sqlite/Mysql to
Datamapper/Bumble+Google Datastore.

Regards,
Chris

4

My workaround in development mode so far: Simply using Webrick as usual
plus setting up the datastore in the controller
(application_controller.rb).

if Rails.env==‘development’
before_filter :setup_datastore
after_filter :teardown_datastore
end

protected

if Rails.env=='development'
  import com.google.apphosting.api.ApiProxy
  import

com.google.appengine.api.datastore.dev.LocalDatastoreService
import com.google.appengine.tools.development.ApiProxyLocalImpl

  class DevEnvironment
    include ApiProxy::Environment
    def app_id
      'Dev Environment'
    end
  end

  def setup_datastore
    ApiProxy.environment_for_current_thread = DevEnvironment.new
    ApiProxy.delegate = Class.new(ApiProxyLocalImpl).new

java.io.File.new(’.’)
#ApiProxy.delegate.set_property
LocalDatastoreService::NO_STORAGE_PROPERTY, ‘true’
end

  def teardown_datastore
    #ApiProxy.delegate.get_service('datastore_v3').clear_profiles
    ApiProxy.delegate = nil
    ApiProxy.environment_for_current_thread = nil
  end
end

Josh M. wrote:

sinatra. I am looking into that now, if you have any insites please

seems to be the need to restart the dev server between code
do with the ORM but is still related to the hot deploy problem
ActiveRecord+Sqlite/Mysql to Datamapper/Bumble+Google Datastore.
    I just finished posting a rails template that creates an app

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