Re: Can a git push over ssh trigger a gc/repack? Diagnosing pack explosion

On Thu, Nov 21, 2013 at 10:21 AM, Martin Langhoff
[off-list ref] wrote:

Do client pushes over git+ssh ever trigger a repack on the server?

man git-config
[snip]

       receive.autogc
           By default, git-receive-pack will run "git-gc --auto" after
           receiving data from git-push and updating refs. You can stop it by
           setting this variable to false.

Oooooops!

Ok, couple problems here:

 - if it's receiving from many pushers, it races with itself; needs
some lock or back-off mechanism

 - alternatively, an splay mechanism. We have a "hard" threshold...
given many "pushers" acting in parallel, they'll all hit the threshold
at the same time. There is no need for this, we could randomize the
threshold by 20%; that would radically reduce the racy-ness

 - auto repack in this scenario has a reasonable likelihood if being
visited by the OOM killer -- therefore it needs to fail more
gracefully, for example with tmpfile cleanup. Perhaps by having the
tmpfiles places in a tmpdir named with the pid of the child would make
this easier...

Naturally, I'll move quickly to disable this evil-spawn-automagic
setting and setup a cronjob. But I think it is possible to have
defaults that work more reliably and with lower risk of explosion.

thoughts?



m
-- 
 martin.langhoff@gmail.com
 -  ask interesting questions
 - don't get distracted with shiny stuff  - working code first
 ~ http://docs.moodle.org/en/User:Martin_Langhoff