On 12/4/2015 10:49 AM, Ulrich Spörlein wrote: > 2015-11-08 12:06 GMT+01:00 Ulrich Spörlein <uqs_at_freebsd.org>: >> 2015-11-08 11:32 GMT+01:00 Ulrich Spörlein <uqs_at_freebsd.org>: >>> 2015-11-08 2:51 GMT+01:00 Alfred Perlstein <alfred_at_freebsd.org>: >>>>> >>>> Uli, >>>> >>>> One of the biggest concerns I've heard from folks using FreeBSD's git mirror >>>> is that the hashes can change. >>>> >>>> I have a question about this. Is it possible to keep track of what the >>>> "official" git mirror (on github) is doing and keep that as a log. Then >>>> that log can be used to replay commits when there is a divergence problem. >>>> >>>> What I'm basically saying is that let's take this small example: >>>> >>>> importer is working fine _at_rev 10000 >>>> imports 10000 >>>> imports 10001 >>>> imports 10002 >>>> something happens to importer to give indeterminate shas. >>>> imports 10003 - sha is "unstable" sha3 >>>> imports 10004 - sha is "unstable" sha4 >>>> imports 10005 - sha is "unstable" sha5 >>>> imports 10006 - sha is "unstable" sha6 >>>> importer is fixed >>>> >>>> >>>> At this point normally we'd rewind the importer to 10002 and then force >>>> update the affected branches. >>>> >>>> My question is... can the imports of 10003, 10004, 10005 and 10006 be put >>>> into the importer such that any "mirror site" that re-does the import using >>>> the most up to date importer will get the same shas. >>>> >>>> That would allow to proceed with 10007, etc without force pushing. >>>> >>>> This should be possible based on querying "git" for the meta data associated >>>> with sha3..sha6 and then forcing those commits to have the same meta data. >>>> >>>> This would eliminate the concern about shas in the mirror changing that I've >>>> heard. >>> >>> The goal of the conversion is that everyone can re-do the conversion >>> in their basement and come up with the same history and checksums. >>> This was not the case when I first started, as there was some >>> non-deterministic hash structure being used in svn2git. This was fixed >>> in the code and then all converter runs produced the very same >>> results. >>> >>> The scenario that we have right now, is that one of the merge commits >>> done about two weeks ago is being handled different by svn2git w/ svn >>> v1.8 vs. svn v1.9 and I haven't investigated yet how the API's >>> behavior changed to cause this. I'm afraid I also swapped out all my >>> knowledge about svn2git internals and will have to redo this all from >>> scratch :/ >>> >>> Your suggestion could only work, if we hard-code this svn revision >>> special handling into svn2git, either in the code or by providing more >>> mappings and rules to the process. svn2git should run hermetic and not >>> poke at github's commits to see how things were handled in the past. >>> It has to be self-sufficient and must not depend on github. >>> >>> This would also only work, if the "breakage" window was very small, >>> but it is already about two weeks long and will surely increase till I >>> find the proper fix. >>> >>> So, to take a stand here: this sort of kludge is unlikely to ever >>> happen. Git commit hashes *might* change in the future. I really don't >>> see how this is a big deal anyway. It happened once and I'm trying to >>> have it never happen again. But why are people afraid of this >>> happening? Every "official" git commit is tagged with a SVN revision >>> and the contents of those revisions are obviously correct (just not >>> the ancestry and the commit objects, possibly). So it would be easy to >>> write a script that replays VendorA's git history and swaps out the >>> new official commits for the old official commits. There would be no >>> merge conflicts. >>> >>> I can see how this would be annoying if you have 100 developers and >>> dozens of branches that are far from mainline FreeBSD. But I'm sure >>> these companies that depend on git will come forward and donate some >>> of their developer manpower to help me with keeping the converter >>> stable/deterministic. Right? Right? :) :) >>> >>> Cheers, >>> Uli >> >> Quick update: doc is so far unaffected by svn 1.9, but for ports, the >> drift happened as of Jul 18, so you'd need to special case a lot of >> commits. >> >> Here's the same commit, and the difference between 1.8 and 1.9: >> >> % git cat-file commit 803795d >> tree 7fc83aba022834da5c218114b09ad4640735bcc0 >> parent c96fb0418e545a569b5975b4d878a30a948c29d5 >> author olgeni <olgeni_at_FreeBSD.org> 1437203525 +0000 >> committer olgeni <olgeni_at_FreeBSD.org> 1437203525 +0000 >> >> Upgrade to version 0.4.1. >> % git cat-file commit 61ca43b >> tree 7fc83aba022834da5c218114b09ad4640735bcc0 >> parent c96fb0418e545a569b5975b4d878a30a948c29d5 >> author olgeni <olgeni_at_FreeBSD.org> 1437203529 +0000 >> committer olgeni <olgeni_at_FreeBSD.org> 1437203529 +0000 >> >> Upgrade to version 0.4.1. >> >> >> In case you don't see it, there's a 4s difference in the timestamps >> for authoring and committing. Here's the original: >> >> % svn log -vc392405 svn://svn.freebsd.org/ports >> ------------------------------------------------------------------------ >> r392405 | olgeni | 2015-07-18 09:12:05 +0200 (Sat, 18 Jul 2015) | 2 lines >> Changed paths: >> M /head/www/elixir-maru/Makefile >> M /head/www/elixir-maru/distinfo >> >> Upgrade to version 0.4.1. >> >> ------------------------------------------------------------------------ >> >> So yeah, svn 1.9 returned a timestamp that was off by 4s. WTF? >> >> For base it's actually even more complicated than I had thought so >> far. But let's take this one step at time ... > > An update, which you won't like to hear: > > SVN v1.9 is totally innocent, the API changed a little and has been > patched, this is not the source of the difference between the > currently published repo and a clean run. The difference stems from > the fact that the svnsync'ed copy on git.freebsd.org was poisoned and > is *NOT* in sync with our main repo. People tell me this is due to a > shortcoming of svnsync that can race and thus produce different > metadata for a commit, depending on when it is run. > > This is a clusterfuck. > > Both freebsd-base and freebsd-ports are no longer reproducible by > third-parties. It is only a matter of time when freebsd-doc is > affected. > > clusteradm_at_ sadly has remained rather silent on this issue and unless > we can move the mirroring to rsync or syncthing or whatever I don't > see how the project can continue to provide a so-called git "mirror" > Running svnsync in 2 places and then calling them mirrors seems odd. It's only needed once. (svnsync hurts global warming too). Then just rsync or use the git mirroring features. -- Regards, Bryan Drewery
This archive was generated by hypermail 2.4.0 : Wed May 19 2021 - 11:41:01 UTC