We were using protocol version 6 but requesting version 4. The only
reason that this worked was because of a broken version check in
'nix-store --serve'. That was fixed in
c2d7456926,
which had the side-effect of breaking hydra-queue-runner.
https://en.wikipedia.org/wiki/HipChat says:
> Following this, HipChat and Stride customers were migrated to the
> Slack group collaboration platform in a transition that was completed by
> February 2019.
NOTE: I'm well-aware that we have to be careful with this to avoid new
regressions on hydra.nixos.org, so this should only be merged after
extensive testing from more people.
Motivation: I updated Nix in my deployment to 2.9.1 and decided to also
update Hydra in one go (and compile it against the newer Nix). Given
that this also updates the C++ code in `hydra-{queue-runner,eval-jobs}`
this patch might become useful in the future though.
I started to wonder quite recently why Hydra doesn't send email
notifications anymore to me. I saw the following issue in the log of
`hydra-notify.service`:
May 22 11:57:29 hydra 9bik0bxyxbrklhx6lqwifd6af8kj84va-hydra-notify[1887289]: fatal: unsafe repository ('/var/lib/hydra/scm/git/3e70c16c266ef70dc4198705a688acccf71e932878f178277c9ac47d133cc663' is owned by someone else)
May 22 11:57:29 hydra 9bik0bxyxbrklhx6lqwifd6af8kj84va-hydra-notify[1887289]: To add an exception for this directory, call:
May 22 11:57:29 hydra 9bik0bxyxbrklhx6lqwifd6af8kj84va-hydra-notify[1887289]: git config --global --add safe.directory /var/lib/hydra/scm/git/3e70c16c266ef70dc4198705a688acccf71e932878f178277c9ac47d133cc663
May 22 11:57:29 hydra 9bik0bxyxbrklhx6lqwifd6af8kj84va-hydra-notify[1886654]: error running build_finished hooks: command `git log --pretty=format:%H%x09%an%x09%ae%x09%at b0c30a7557685d25a8ab3f34fdb775e66db0bc4c..eaf28389fcebc2beca13a802f79b2cca6e9ca309 --git-dir=.git' failed with e>
This is also a problem because of Git's fix for CVE-2022-24765[1], so I
applied the same fix as for Nix[2], by using `--git-dir` which skips the
code-path for the ownership-check[3].
[1] https://lore.kernel.org/git/xmqqv8veb5i6.fsf@gitster.g/
[2] https://github.com/NixOS/nix/pull/6440
[3] To quote `git(1)`:
> Specifying the location of the ".git" directory using this option
> (or GIT_DIR environment variable) turns off the repository
> discovery that tries to find a directory with ".git" subdirectory
On hydra.nixos.org the queue runner had child processes that were
stuck handling an exception:
Thread 1 (Thread 0x7f501f7fe640 (LWP 1413473) "bld~v54h5zkhmb3"):
#0 futex_wait (private=0, expected=2, futex_word=0x7f50c27969b0 <_rtld_local+2480>) at ../sysdeps/nptl/futex-internal.h:146
#1 __lll_lock_wait (futex=0x7f50c27969b0 <_rtld_local+2480>, private=0) at lowlevellock.c:52
#2 0x00007f50c21eaee4 in __GI___pthread_mutex_lock (mutex=0x7f50c27969b0 <_rtld_local+2480>) at ../nptl/pthread_mutex_lock.c:115
#3 0x00007f50c1854bef in __GI___dl_iterate_phdr (callback=0x7f50c190c020 <_Unwind_IteratePhdrCallback>, data=0x7f501f7fb040) at dl-iteratephdr.c:40
#4 0x00007f50c190d2d1 in _Unwind_Find_FDE () from /nix/store/65hafbsx91127farbmyyv4r5ifgjdg43-glibc-2.33-117/lib/libgcc_s.so.1
#5 0x00007f50c19099b3 in uw_frame_state_for () from /nix/store/65hafbsx91127farbmyyv4r5ifgjdg43-glibc-2.33-117/lib/libgcc_s.so.1
#6 0x00007f50c190ab90 in uw_init_context_1 () from /nix/store/65hafbsx91127farbmyyv4r5ifgjdg43-glibc-2.33-117/lib/libgcc_s.so.1
#7 0x00007f50c190b08e in _Unwind_RaiseException () from /nix/store/65hafbsx91127farbmyyv4r5ifgjdg43-glibc-2.33-117/lib/libgcc_s.so.1
#8 0x00007f50c1b02ab7 in __cxa_throw () from /nix/store/dd8swlwhpdhn6bv219562vyxhi8278hs-gcc-10.3.0-lib/lib/libstdc++.so.6
#9 0x00007f50c1d01abe in nix::parseURL (url="root@cb893012.packethost.net") at src/libutil/url.cc:53
#10 0x0000000000484f55 in extraStoreArgs (machine="root@cb893012.packethost.net") at build-remote.cc:35
#11 operator() (__closure=0x7f4fe9fe0420) at build-remote.cc:79
...
Maybe the fork happened while another thread was holding some global
stack unwinding lock
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71744). Anyway, since
the hanging child inherits all file descriptors to SSH clients,
shutting down remote builds (via 'child.to = -1' in
State::buildRemote()) doesn't work and 'child.pid.wait()' hangs
forever.
So let's not do any significant work between fork and exec.
Re-executing this search_related on every access turned out to
create very problematic performance. If a jobset had a lot of
error output stored in the jobset, and there were many hundreds
or thousands of active jobs, this could easily cause >1Gbps of
network traffic.
Maximilian Bosch
Ilya K