I've played with libvirt-slave-plugin today to make it work with libvirt/bhyve and decided to document my steps in case it would be useful for somebody.
Assuming that you already have Jenkins up and running, installation of libvirt-slave-plugin is as follows. As we need a slightly modified version, we need to build it ourselves. I've made a fork which contains a required modification which could be cloned like that:
git clone -b bhyve firstname.lastname@example.org:jenkinsci/libvirt-slave-plugin.git
The only change I made is adding a single line with 'BHYVE' hypervisor type, you could find the pull request here. When that would be merged, this step will be not required.
So, getting back to the build. You'll need maven that could be installed from ports:
cd /usr/ports/devel/maven2 && make install clean
When it's installed, go back to the plugin we cloned and do:
mvn package -DskipTests=true
When done, login to the Jenkins web interface, go to Manage Jenkins -> Manage Plugins -> Advanced -> Upload Pluging. It'll ask to provide a path to the plugin. It would be target/libvirt-slave.hpi in our plugin directory.
After plugin is installed, please follow to Manage Jenkins -> Configure System -> Add new cloud. Then you'll need to specify hypervisor type BHYVE and configure credentials so Jenkins could reach your libvirtd using SSH. There's a handy 'Test Connection' you could use your configuration.
Once done with that, we can go to Manage Jenkins -> Manage Nodes -> New Node and choose 'libvirt' node type. Then you'll need to choose a libvirt domain to use for the node. From now on, node configuration is pretty straightforward, expect, probably an IP address of the slave. To find out an IP address, you'd need to find out its MAC address (just run virsh dumpxml and you'll find it there) and then find the corresponding file in dnsmasq/default.leases file.
The only thing guest OS needs is to have jdk installed. I preferred to download a package with java/openjdk7, but I had to configure network first. My VMs use bridged networking on virbr0, so NAT config looks like that in /etc/pf.conf:
ext_if="re0" int_if="virbr0" virt_net="192.168.122.0/24" scrub all nat on $ext_if from $virt_net to any -> ($ext_if)
Now openjdk could be installed from the guest using:
pkg install java/openjdk7
Finally, find the nodes in node management menu and press 'Launch slave agent' button. It should be ready for the builds now.
PS It might be useful to sync clock on both guest and host systems using ntpdate.
PPS libvirt version should be at least 1.2.2.