way to limit number of revisions processed during fetch

[Jelmer Vernooij]

bzr-svn/bzr-hg/bzr-git currently support an optional "limit" parameter to their Branch.pull functions that allows limiting the number of revisions fetched. This is used so that on the launchpad importer service the import slaves don't get blocked by a single process.

Previously this code worked using a hack that assumed the last revision fetched was the tip of the branch if all revisions were fetched. Now that tags are being fetched this is no longer true.

It would be nice to have this sort of infrastructure in Bazaar itself, perhaps using a limit= argument to Repository.fetch()

[Michael Hudson-Doyle (mwhudson)]

I guess if you're looking at this again, I'd say that what the code importers really care about is to limit the _time_ spent processing revisions during fetch. This might even be useful for people who are pulling large branches over low-bandwidth links, rather than running bzr pull -r 1000; bzr pull -r 2000; and so on, but that's perhaps going off into lala land.

Yay for fixing this problem without hacks though.

[Jelmer Vernooij (jelmer)]

We considered other options, but having a "timelimit" option or something like that is going to be awkward to implement and test; this seems to work reasonably well at the moment and is also fairly easy to implement. From Launchpad's POV there's probably also the memory usage that needs to be limited.

Alternatively, perhaps we could remember in launchpad how long the last run took per revision, and use that to adjust the limit?