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.
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my $drvpath = $build->drvpath;
my @paths = reverse(split '\n', `nix-store -qR $drvpath`);
my $depBuild;
my @drvs = ();
foreach my $path (@paths) {
push @drvs, $path if $path =~ /\.drv$/ && $path ne $drvpath;
}
return unless scalar @drvs > 0;
($depBuild) = $db->resultset('Builds')->search(
{ drvpath => [ @drvs ], finished => 0, busy => 0, enabled => 1, disabled => 0 },
{ join => ['project'], rows => 1 } ) ;
return $depBuild;
my @deps = grep { /\.drv$/ && $_ ne $build->drvpath } computeFSClosure(0, 0, $build->drvpath);
return unless scalar @deps > 0;
return $db->resultset('Builds')->search(
{ drvpath => [ @deps ], finished => 0, enabled => 1, disabled => 0 },
{ join => ['project'], rows => 1 })->single;
my $depbuild = findBuildDependencyInQueue($build);
$build = $depbuild if defined $depbuild;
# Find a dependency of $build that has no queued
# dependencies itself. This isn't strictly necessary,
# but it ensures that Nix builds are done as part of
# their corresponding Hydra builds, rather than as a
# dependency of some other Hydra build.
while (my $dep = findBuildDependencyInQueue($build)) {
$build = $dep;
}
next if $build->busy;