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-imagesallows an archive file of docker images to be included in the dib image
install.d/50-heat-config-kubeletinstalls 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.pypolls docker images and containers until the expected kubelet-provisioned containers are running (or a timeout occurs)
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