On Oct 8, 11:17 am, Jon McAlister <[EMAIL PROTECTED]> wrote: > Regarding the CDN case is markedly different from the datastore case, > since you're just dealing with immutable blobs. This is not the thorny > issue.
I think I've got an idea. If there is a major problem that takes all the servers that are able to serve my app offline, it would be nice if the app could still operate in read-only mode from a backup data center on another continent. Many apps can indeed stay useful in read-only mode. And it might significantly alleviate the pain of service disruption for users. This looks like a feasible thing to implement. I'll describe it from the point of view of a single app. Several backup snapshots of the datastore could be continually maintained in remote data centers. The snapshots would lag behind the master copy a minute or two (or more), so they wouldn't have to be located close to the master copy, which is the point. When a severe service disruption affecting all master data centers is detected, the app's DNS quickly fails over to a backup data center, where the app continues to run in read-only mode using the last datastore snapshot. The application should detect the read-only mode to make sure it doesn't try to write anything to the database and to inform the users. When the problems have been settled, the app reverts to normal read- write mode. Most of the time the old master data center would take over. If it has been destroyed or something, one of the backup data centers could be manually made the master for this particular app. In that case, several minutes worth of data would be lost, but that seems acceptable for a complete destruction of the original data centers. I don't know whether there are serious holes in this outline, because I'm not really a distributed systems guy. Does it make sense? Jon, do you think it's worth to file an issue about this? -- Alexander --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
