CloudFlare with Google App Engine overquota

Question

I've been looking at CloudFlare as a CDN service for my Google App Engine hosting, and as a student, cost is always an issue (aka free services only). I read on the CF blog that when the origin server is down, CF will serve a cached version of the website from its own servers to users.

So if we hit the GAE quota limit, is the server considered as "down"? Will CF display the cached website? I don't plan to have a lot of dynamic content so serving an entire cached website is not too much of an issue to me.

If the answer to my first question is no, is it possible to get CF to serve it's cached website content automatically once GAE hits any quota limit? I know it's probably unlikely but just wanted to throw this question out.

Answer 1

According to CloudFlare's wiki, the Always Online feature will return a cached page only if the backend server is unavailable or returns a response code of 502 or 504. When you hit quota limits App Engine itself will generally still be available, so whether the cache works depends on the response code in your case.

If your app exceeds its bandwidth or instance hour quota, App Engine will return a 403 Forbidden response code. It is possible to customize the content of the error response, but not the code. It seems then that CloudFlare will not serve a cached page in this case.

However, if your app hits an API usage quota, your code will receive an exception and you can choose to return one of those 50x codes and trigger the cache.

Answer 2

I'm not sure if this particular case will work for CloudFlare because of the error code that App Engine returns (we are working on some enhancements for Always Online, but it really won't tackle 403 errors).

It does appear that AppEngine does allow you some customization of the error pages?

Tip: You can configure your application to serve a custom error page when your application exceeds a quota. For details, see Custom Error Responses documentation for Python and Java.