Ben Reser <b...@reser.org> writes: >> I think part of the problem here has been we (as in WANdisco folks) have >> discussed the idea of an instance ID for repositories in the past to solve >> the range of replacing the repository without clearing the cache issues. >> But this change is being added for a very different reason. >> >> Evgeny has implemented the instance ID for the purpose of solving the problem >> of two different repositories not being able to be locked if they happen to >> have the same UUID. This happens because we use a mutex to handle locking >> between threads and that mutex can't distinguish between different >> repositories with identical UUIDs. >> >> Currently the code on trunk adds the instance ID to the cache keys. I'm not >> sure we should be doing that (though both brane and stefan2 requested that be >> done). As per the discussion today at the SHF hackathon the instance ID >> can't resolve the failure to clear the cache issues. The best it can do is >> narrow the window for these issues to exist. That would seem like a good >> thing but I think it creates a huge false sense of security. We will >> ultimately have someone that comes along with a corrupted repository, we're >> going to say you replaced the repo while the server was running and the user >> is going to say "But I've been doing this for years without any problem." >> >> Without the instance ID in the cache keys users are unlikely to actually >> corrupt their repository (just like they would be with them, it's a pretty >> hard race to hit). But they are likely to get errors related to the cache >> being stale. This gives them a giant hint that what they're doing is wrong >> and gives us an opportunity to educate them. > > Evgeny do you have any thoughts on this? I think it's probably best to remove > the instance id from the cache keys. I believe brane and stefan2 were > convinced of this at the hackathon.
Sounds good to me. However, prior to (re-)narrowing the scope of this change, I would love to spend a bit of time and actually reproduce the repository corruption race (with or without instance IDs) — just in order to obtain a bit of information, which I currently lack. I plan to undo the corresponding part of the changeset right after that. Regards, Evgeny Kotkov
