gc does not clean up after itself when not enough disk space

When git gc fails on no more disk space, it leaves tmp_pack files lying around that consume whatever space was available (and fill up the disk to 100%). Shouldn't git be deleting these files?

Running git 1.7.9 on cygwin:

# git --version
git version 1.7.9
# uname -a
CYGWIN_NT-6.1-WOW64 ---- 1.7.17(0.262/5/3) 2012-10-19 14:39 i686 Cygwin

Example failure output:

# git gc
Counting objects: 44626, done.
Delta compression using up to 8 threads.
Compressing objects: 100% (7756/7756), done.
fatal: sha1 file '.git/objects/pack/tmp_pack_uJ0E5b' write error: No space left on device
error: failed to run repack

Thanks!
Noam

In general when we encounter an unexpected error, we tend to try leaving things as they are so that we can help diagnosing the failure. But when you ran out of disk space I would agree that it may be sensible to remove a temporary file we didn't manage to write out in full.

Am 26.02.2013 17:07, schrieb Junio C Hamano:

Ack. I just recently had to do

   git gc || rm -f .git/objects/*/tmp_*

as workaround in the nightly housekeeping script on our CI server.

it's not just 'git gc'; a failed push of a large repo (failed due to, say, network issues or whatever) also leave tmp_* lying around. At least as far as I can tell...

Yes, we used to run into problems with failed pushes sometimes at GitHub. A later git gc will clean up the tmp_* objects (via git prune), but of course we will not run the prune if the repack fails. Also note that a push will just keep receiving objects as long as the client wishes to send them, spooling straight to disk, before any enforcement hooks have a chance to run. So on stock git, you could in theory just fill up the receiver's disk, and then git will leave the file sitting around.

I have a patch to make index-pack just do a hard hangup after receiving receive.maximumBytes bytes (with an appropriate message to stderr). It's not an exact measure of the size of the push (since we need to complete thin packs, and we may also explode smaller packs), but it at least bounds the size that the sender can push. I'm happy to share the patch if others are interested (it's only a few lines).

I've also considered a patch to have index-pack clean up tmp_pack_* automatically on exit, default to off (i.e., the current behavior). A busy site could turn it on globally, and then shut it off for a specific repo when trying to debug a push problem. I find that the leftover tmp_pack files are very seldom of interest for forensic debugging. I haven't bothered to write that patch, though; we dropped our prune expiration time well below the 2-week default, so the tmp files get cleaned up pretty regularly now.

-Peff