Previously this function didn't actually have a lot of effect. If a
build A had a dependency B, Hydra would start B first. But on the
next scan through the queue, it would start A anyway, because of the
"busy => 0" restriction.
Now the queue runner won't start a build if a dependency is already
running. (This is not necessarily optimal, since the build may have
other dependencies that don't correspond to a build in the queue but
could run. One day we'll start all Hydra builds in parallel...)
Also, for performance, use computeFSClosure instead of "nix-store
-qR". And don't bother with topological sorting because it didn't
have an effect anyway since the database returns dependencies in
arbitrary order.
This allows checking a jobset (say) at most once a day. It's also
possible to disable polling by setting the interval to 0. This is
useful for jobsets that use push notification or are manually
evaluated.
This caused exceptions like:
Caught exception in Hydra::Controller::Build->view_build "writing to file: Broken pipe at /nix/store/ihdb3widsq1dk7sbl5vqjxfcxb5ypad4-hydra-0.1pre1297-8158093/libexec/hydra/lib/Hydra/Controller/Build.pm line 59."
because the connection to the Nix daemon would be terminated due to a
protocol violation (calling queryPathInfo with an empty string).
Returning only the first 20 results can cause NixOS/Nixpkgs channel
generation to fail, if the first 20 view results correspond to
evaluations that haven't finished yet. Then URLs like
/view/nixos/tested/latest-finished will return 500 rather than the
latest finished view.
You can now do:
bash <(curl http://hydra-server/build/1238757/reproduce)
to download and execute a script that reproduces a Hydra build
locally. This script fetches all inputs (e.g. Git repositories) and
then invokes nix-build.
The downloaded sources are stored in /tmp/build-<buildid> and reused
between invocations of the script.
Any additional command line options are passed to nix-build. So
bash <(curl http://hydra-server/build/1238757/reproduce) --run-env
will drop you in a shell where you can interactively hack on the
build, e.g.
$ source $stdenv/setup
$ set +e
$ unpackPhase
$ cd $sourceRoot
$ configurePhase
$ emacs foo.c &
$ make
and so on.
Build product paths cannot reference locations outside of the Nix
store. We previously disallowed paths from being symlinks, but this
didn't take into account that parent path elements can be symlinks as
well. So a build product /nix/store/bla.../foo/passwd, with
/nix/store/bla.../foo being a symlink to /etc, would still work.
So now we check all paths encountered during path resolution.
Symlinks are allowed again so long as they point to the Nix store.
