- Use the type itself
This lays the foundation for being able to dedup the protocol code.
- Use `BasicConnection::handshake`, replacing ours.
- Use `BasicConnection::queryValidPaths`
- Use `BasicConnection::putBuildDerivationRequest`
Instead of doing this partial operation a number of times, assert (with
a comment, get a reference to the thing inside, and use that just once.
(This refactor was done twice, "just once" for each time.)
Both sides need to agree on a version (with `std::min`) for anything to
work. Somehow... we've never done this.
With this comment, the next commit succeeds. Without this commit, the
next commit fails. This is because the next commit exposes serializers
which do different things for proto version 2.7, and we're currently
requesting 2.6.
Opened https://github.com/NixOS/nix/issues/9584 to track this issue
The point of this branch is to always track Nix master, so we are
proactively ready to upgrade to the next Nix release when it is ready.
Flake lock file updates:
• Updated input 'nix':
'github:NixOS/nix/50f8f1c8bc019a4c0fd098b9ac674b94cfc6af0d' (2023-11-27)
→ 'github:NixOS/nix/c3827ff6348a4d5199eaddf8dbc2ca2e2ef46ec5' (2023-12-07)
• Added input 'nix/libgit2':
'github:libgit2/libgit2/45fd9ed7ae1a9b74b957ef4f337bc3c8b3df01b5' (2023-10-18)
For the record, here is the Nix 2.19 version:
https://github.com/NixOS/nix/blob/2.19-maintenance/src/libstore/serve-protocol.cc,
which is what we would initially use.
It is a more complete version of what Hydra has today except for one
thing: it always unconditionally sets the start/stop times.
I think that is correct at the other end seems to unconditionally
measure them, but just to be extra careful, I reproduced the old
behavior of falling back on Hydra's own measurements if `startTime` is
0.
The only difference is that the fallback `stopTime` is now measured from
after the entire `BuildResult` is transferred over the wire, but I think
that should be negligible if it is measurable at all. (And remember,
this is fallback case I already suspect is dead code.)
The previous implementation was O(N²lg(N)) due to sorting the full
runnables priority list once per runnable being scheduled. While not
confirmed, this is suspected to cause performance issues and
bottlenecking with the queue runner when the runnable list gets large
enough.
This commit changes the dispatcher to instead only sort runnables per
priority once per dispatch cycle. This has the drawback of being less
reactive to runnable priority changes: the previous code would react
immediately, while this might end up using "old" priorities until the
next dispatch cycle. However, dispatch cycles are not supposed to take
very long (seconds, not minutes/hours), so this is not expected to have
much or any practical impact.
Ideally runnables would be maintained in a sorted data structure instead
of the current approach of copying + sorting in the scheduler. This
would however be a much more invasive change to implement, and might
have to wait until we can confirm where the queue runner bottlenecks
actually lie.
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.
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.
