Sinatra on Google App Engine

Monday 05/18/2009  –  Category: Uncategorized

I attended a JRuby on Google App Engine talk during Railsconf and have been anxious to try deploying a Ruby application on the platform.  This tutorial gives a good walkthrough and I was able to get a Sinatra app up and running on GAE, but not without a few hiccups and hurdles.

Some things I ran across:

• You need to have Java enabled on your GAE account.  It can take up to a few days to get approved for the early look program.
• The rflickr gem I'm using in my Sinatra app relies on on xmlrpc and net:http which can't be used on GAE and was raising this error:

  java.security.AccessControlException: access denied (java.lang.RuntimePermission modifyThreadGroup)

• Since GAE uses its own URL fetch library in place of net/http, you can get xmlrpc to work by doing this (thanks Ryan Brown!):

require 'appengine-apis/urlfetch'
Net::HTTP = AppEngine::URLFetch::HTTP

• After I did that, the thread error went away, but I got a different error:

NoMethodError - undefined method `as_java_bytes' for #<String:0x440543>

• This time it was just a typo in the appengine-apis-0.0.4 gem.  line 142 of urlfetch.rb needs to be:

request.set_payload(payload.to_java_bytes)

instead of

request.set_payload(payload.as_java_bytes)

• It takes quite a while to spin up the app for the first request...I'm not sure if there's any way around that other than setting up something to ping the app every so often