This hook uses the kubelet agent from the kubernetes project to provision containers. The StructuredConfig resource data represents a pod of containers to be provisioned.

The files have the following purpose:

  • extra-data.d/50-docker-images allows an archive file of docker images to be included in the dib image

  • install.d/50-heat-config-kubelet installs kubernetes for redhat based distros during dib image build, along with the required systemd and config files required to enable a working kubelet service on the host

  • install.d/hook-kubelet.py polls docker images and containers until the expected kubelet-provisioned containers are running (or a timeout occurs)

  • os-refresh-config/configure.d/50-heat-config-kubelet runs before 55-heat-config (and the kubelet hook it triggers). This orc script writes out all pod definition files for the pods that should currently be running. Kubelet is configured to monitor the directory containing these files, so the current running containers will change when kubelet acts on these config changes