I recently launched a site on Google App Engine using Python. I'm in Korea, but my client is in California, USA. He and others in his area periodically run into periods of time when they receive this error message instead of the site:
This website is temporarily unavailable, please try again later.
I cannot figure out what is causing this. At first I was getting some errors due to the datastore timing out, but I found a fix for that. Then I thought that it was a problem with a particular area of the site that was taking up a lot of CPU time, but SO helped me there. And in any case with the small amount of traffic this site is receiving there was no danger of going over the quotas, anyways.
When my client is running into this problem (I have not personally experienced it) they get it every time they try to access the site for a period of time. Usually these periods last around 20 minutes and then the site is okay to access again.
My client has experienced this at his work as well as from his home. But at his home he has two computers, a server that is connected directly to a cable modem and then another that is connected through a router. The server has yet to experience this problem but his other computer does experience this problem consistently with someone else's at a different location.
I'm not receiving any errors in the admin console and only two of the paths get occasional warnings about CPU time.
Update
It's been a while (nearly 3 weeks) and the user hasn't reported this problem again. Maybe it was just some temporary issue with GAE's servers in that area (California, USA)? I dunno, but I can't really move forward on this without more clues. Thanks to those who tried to help. If it comes up again I'll come back here.