I have two machines scheduled to backup daily to Rackspace. One has a much larger backup set than the other. Besides that, there are no other relevant differences between the machines that I know of. The machine with the larger backup set is the one at issue. I've recently discovered that Deja Dup is silently failing to upload the backups. By that, I mean that Deja Dup gives every appearance of success (my network monitor even shows appropriate network traffic), and I can't find anything amiss in the debug log (though since it's > 3m lines long, I might have missed something). However, despite the lack of error messages, there's also no success confirmation, and the files are demonstrably not on Rackspace.
I suspect that there's some error, but is there appropriate error checking? It would appear that there isn't.
Here's some additional info. I don't know whether it belongs here or in a separate bug. According to the Rackspace Cloud Files documentation, a single file listing will return a maximum of 10,000 files and states that multiple requests are necessary if there are more than 10,000 files. But Deja Dup apparently only makes a single request and suspiciously retrieves exactly 10,000 files from that request.
I've previously reported bug 824583 and bug 824570. I think that this bug goes a long way in explaining the previous bugs. The only part of the requested standard info I'm including with this bug is a full log file showing the upload apparently succeeding (although the files aren't on Rackspace). I'm not duplicating the other info since you can find it in the other bugs I reported.
Finally, I contacted Rackspace to see if they had any relevant logs. They don't.
Great research, Scott! I bet you're right, that the duplicity rackspace backend is not making multiple requests. I'll look at it.