Stabilizing a fragile web application by proxy

I'm having an unstable dynamic web application which I want to stabilize by running in this settings:

1. Given a GET request to url U I will
   1. Look for U in the cache - if it's already there - fetch it from the cache
   2. If it's not, generate the cache from the web application.
2. Administrator will be able to access the web application directly. Whenever he will access a webpage - the generated web page will be used to update the cache.

This way, I know for sure that even if the web application is down, most of the pages will still be accessible. And it is easy for the administrator to update the cache (whenever he edits something there - it'll be updated automatically, since he'开发者_如何学Cll usually access this page afterwards).

Is there a generic cache with similar behavior? Any better ideas for stabilizing existing web application without changing its source code?