bug#34016: Git checkouts managed by (guix git) grow indefinitely?

[Ludovic Courtès]

Hello,

On berlin I noticed that Cuirass would run out of file descriptors
almost immediately once started.  I managed to get the list of open
files:

--8<---------------cut here---------------start------------->8---
address@hidden ~$ sudo ls -l /proc/$(sudo herd status cuirass|grep value|sed 
-es'/^.* \([0-9]\+\)\.$/\1/g')/fd
[…]
alwq/.git/objects/pack/pack-dde01a576697a783fd12eb73228921153ba18b4b.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 978 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-d65f5c22414e4864a00ec7bee4cff5ff0b4a2c31.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 979 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-d78f9f47a68d4254a81d57d6183fe9c9be41752d.pack
l-wx------ 1 cuirass cuirass 64 Jan  8 17:46 98 -> 'pipe:[70917334]'
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 980 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-58f83b77dbe392bba277f10a1bdd7ed469946feb.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 981 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-d28d075e1dd259683747b5723a232fa4d60cd1a9.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 982 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-cffbdad6def559b60bd928173916f3edbb1a4a8f.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 983 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-ac42d4dd95b02bb54d03687c984c67bacf0e1feb.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 984 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-e5e26a7aeb5a33889f6ac8cff8bef182b5b8a0b2.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 985 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-ac66439d6b07a0e4cf2e4ccef3be21e8a1c96d55.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 986 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-f73b60b056634b58f44fb65f20416e22a6c936e8.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 987 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-f8f3313f5ec872e43cb1e12a8b6509e7f0a13512.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 988 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-55e720e2a4ec09cc996599c5089be871eba8f829.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 989 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-d2441e647df889422906a30d06d6d195e522cbd1.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 99 -> 'pipe:[70908233]'
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 990 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-61fed4082491ff66716c92fe49fe499cd6a5fa78.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 991 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-0bcefb4f7953471a0bc944f0f0c3bbe9143df22b.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 992 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-6a5fbea2046bdc8c94926e9d3d516e1b5351b645.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 993 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-add66d8bdd96e4cc67e78a23c428f7b4e46974df.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 994 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-740728c75faa0e9179ad977d4e4b2eb6bfa51345.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 995 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-c78417a98abdc6a7396fb3f6e4d5633de20c819c.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 996 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-df4cae77b58d600538f2dc51b7b31b61a92cab23.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 997 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-83559c192d41400596d42587bb50d409c121969d.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 998 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-1f46268a2ba6bd3b97d9d7cea4e18233212cc75e.pack
lr-x------ 1 cuirass cuirass 64 Jan  8 17:46 999 -> 
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq/.git/objects/pack/pack-55a94a468fa892b0128656fc5aa953c667161fcd.pack
--8<---------------cut here---------------end--------------->8---

So it’s Guile-Git, called from ‘update-cached-checkout’¹, that would open
all these pack files, quickly running out of file descriptors.  I wonder
if we’re doing something wrong here or if we hit a limitation of
libgit2.  Ideas?

In the meantime, the obvious workaround was to “rm -rf
/var/cache/cuirass/pjmkglp4t7znuugeurpurzikxq3tnlaywmisyr27shj7apsnalwq”.

Thanks,
Ludo’.

¹ https://git.savannah.gnu.org/cgit/guix.git/tree/guix/git.scm#n122