This is mostly so we don't have to pass around common parameters like
"db" and "config", and we don't have to check for the existence of
methods.
A plugin now looks like this:
package Hydra::Plugin::TwitterNotification;
use parent 'Hydra::Plugin';
sub buildFinished {
my ($self, $build, $dependents) = @_;
print STDERR "tweeting about build ", $build->id, "\n";
# Send tweet...
# Hydra database is $self->{db}.
}
You can now add plugins to Hydra by writing a module called
Hydra::Plugin::<whatever> and putting it in Perl's search path. The
only plugin operation currently supported in buildFinished, called
when hydra-build has finished doing a build.
For instance, a Twitter notification plugin would look like this:
package Hydra::Plugin::TwitterNotification;
sub buildFinished {
my ($self, $db, $config, $build, $dependents) = @_;
print STDERR "tweeting about build ", $build->id, "\n";
# send tweet...
}
1;
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.
Avoid the frequently printed
hydra-queue-runner[10293]: system type `x86_64-linux': 2 active, 2 allowed, starting 0 builds
message. That information is only interesting when some build are
actually started.
