On Fri, Sep 06, 2019 at 05:04:17PM -0400, Derrick Stolee wrote: > On 9/6/2019 4:42 PM, Junio C Hamano wrote: > > Jeff King <p...@peff.net> writes: > > > >> I suppose so. But I think the "stock git without any other job > >> infrastructure" case would still benefit. > > > > Oh, no question about it. > > > > I did question if an automatic writing would benefit the side that > > receives a push when you brought up the usual "fetch.* and receive.* > > for separate configuration, transfer.* when want to rule them both" > > convention, which is a good idea if only for consistency, but the > > question was if it helps the receiving end of a push to the same > > degree as it would help the repository that fetches. > > I think the "stock git without any other job infrastructure" is > a very important scenario. Putting the simplest version of > "commit-graph writes in-line with every push" seems to be ripe > for failure under load. I'd rather think deeply about what is > best for this scenario.
If it's going to be a problem under load, that makes me worry about the same thing for fetches. Whether you see a lot of either depends on your workflow. But as long as neither option is enabled by default (or at least if it becomes common knowledge to _disable_ them if you have a high rate), it may be OK. I do agree that the normal "busy" repos you and I have both seen in enterprise settings (where people are literally pushing multiple times per second at peak) would want some kind of throttling. But I think there's a long tail of "push once a week" repos. > Spit-balling: what if we used the same mechanism as running GC > in the background to launch 'git commit-graph write' commands? > And we could have the command give up (without failure) if the > commit-graph.lock file is already created, so concurrent pushes > would not fight each other. I have mixed feelings. It's nice not to stand in the critical path of the user, but background tasks have a way of finding funny corner cases (e.g., packfiles moving around, or the issues we've had with deciding when to shut down auto-gc for a grace period due to warnings/errors). I think since this is generally additive (adding new commit-graph files), it might be less finicky, though. -Peff
