* Set small CPU requests on static pods kube-apiserver,
kube-controller-manager, and kube-scheduler to align with
upstream tooling and for edge cases
* Effectively, a practical case for these requests hasn't been
observed. However, a small static pod CPU request may offer
a slight benefit if a controller became overloaded and the
below mechanisms were insufficient
Existing safeguards:
* Control plane nodes are tainted to isolate them from
ordinary workloads. Even dense workloads can only compress
CPU resources on worker nodes.
* Control plane static pods use the highest priority class, so
contention favors control plane pods (over say node-exporter)
and CPU is compressible too.
See: https://github.com/poseidon/terraform-render-bootstrap/pull/161
* Update terraform-render-bootstrap module to adopt the
Terrform v0.12 templatefile function feature to replace
the use of terraform-provider-template's `template_dir`
* Require Terraform v0.12.6+ which adds `for_each`
Background:
* `template_dir` was added to `terraform-provider-template`
to add support for template directory rendering in CoreOS
Tectonic Kubernetes distribution (~2017)
* Terraform v0.12 introduced a native `templatefile` function
and v0.12.6 introduced native `for_each` support (July 2019)
that makes it possible to replace `template_dir` usage
* Define bare-metal `controllers` and `workers` as a complex type
list(object{name=string, mac=string, domain=string}) to allow
clusters with many machines to be defined more cleanly
* Remove `controller_names` list variable
* Remove `controller_macs` list variable
* Remove `controller_domains` list variable
* Remove `worker_names` list variable
* Remove `worker_macs` list variable
* Remove `worker_domains` list variable
* Review variables available in bare-metal kubernetes modules
for Container Linux and Fedora CoreOS
* Deprecate cluster_domain_suffix variable
* Remove deprecated container_linux_oem variable
* Fix issue (present since bootkube->bootstrap switch) where
controller asset copy could fail if /etc/kubernetes/manifests
wasn't created in time on platforms using path activation for
the Kubelet (observed on DigitalOcean, also possible on
bare-metal)
* Drop `node-role.kubernetes.io/master` and
`node-role.kubernetes.io/node` node labels
* Kubelet (v1.16) now rejects the node labels used
in the kubectl get nodes ROLES output
* https://github.com/kubernetes/kubernetes/issues/75457
* Rename render module from bootkube to bootstrap. Avoid
confusion with the kubernetes-incubator/bootkube tool since
it is no longer used
* Use the poseidon/terraform-render-bootstrap Terraform module
(formerly poseidon/terraform-render-bootkube)
* https://github.com/poseidon/terraform-render-bootkube/pull/149
* Run a kube-apiserver, kube-scheduler, and kube-controller-manager
static pod on each controller node. Previously, kube-apiserver was
self-hosted as a DaemonSet across controllers and kube-scheduler
and kube-controller-manager were a Deployment (with 2 or
controller_count many replicas).
* Remove bootkube bootstrap and pivot to self-hosted
* Remove pod-checkpointer manifests (no longer needed)
* Run a kube-apiserver, kube-scheduler, and kube-controller-manager
static pod on each controller node. Previously, kube-apiserver was
self-hosted as a DaemonSet across controllers and kube-scheduler
and kube-controller-manager were a Deployment (with 2 or
controller_count many replicas).
* Remove bootkube bootstrap and pivot to self-hosted
* Remove pod-checkpointer manifests (no longer needed)
* Run a kube-apiserver, kube-scheduler, and kube-controller-manager
static pod on each controller node. Previously, kube-apiserver was
self-hosted as a DaemonSet across controllers and kube-scheduler
and kube-controller-manager were a Deployment (with 2 or
controller_count many replicas).
* Remove bootkube bootstrap and pivot to self-hosted
* Remove pod-checkpointer manifests (no longer needed)
* For Fedora CoreOS, only HTTPS downloads are available.
Any iPXE firmware must be compiled to support TLS fetching.
* For Container Linux, using public kernel/initramfs images
defaults to using HTTPS, but can be set to HTTP for iPXE
firmware that hasn't been custom compiled to support TLS
* Kubelets can hit the ContainerManager Delegation issue and fail
to start (noted in 72c94f1c6). Its unclear why this occurs only
to some Kubelets (possibly an ordering concern)
* QoS cgroups remain a goal
* When a controller node is affected, bootstrapping fails, which
makes other development harder. Temporarily disable QoS on
controllers only. This should safeguard bring-up and hopefully
still allow the issue to occur on some workers for debugging
* Use the xz compressed images published by Fedora testing,
instead of gzippped tarballs. This is possible because the
initramfs now supports xz and coreos-installer 0.8 was added
* Separate bios and uefi raw images are no longer needed
* First semi-working cluster using 30.307-metal-bios
* Enable CPU, Memory, and BlockIO accounting
* Mount /var/lib/kubelet with `rshare` so mounted tmpfs Secrets
(e.g. serviceaccount's) are visible within appropriate containers
* SELinux relabel /etc/kubernetes so install-cni init containers
can write the CNI config to the host /etc/kubernetes/net.d
* SELinux relabel /var/lib/kubelet so ConfigMaps can be read
by containers
* SELinux relabel /opt/cni/bin so install-cni containers can
write CNI binaries to the host
* Set net.ipv4_conf.all.rp_filter to 1 (not 2, loose mode) to
satisfy Calico requirement
* Enable the QoS cgroup hierarchy for pod workloads (kubepods,
burstable, besteffort). Mount /sys/fs/cgroup and
/sys/fs/cgroup/systemd into the Kubelet. Its still rather racy
whether Kubelet will fail on ContainerManager Delegation
* Allow updating terraform-provider-ct to any release
beyond v0.3.2, but below v1.0. This relaxes the prior
constraint that allowed only v0.3.y provider versions
* Run kube-apiserver as a non-root user (nobody). User
no longer needs to bind low number ports.
* On most platforms, the kube-apiserver load balancer listens
on 6443 and fronts controllers with kube-apiserver pods using
port 6443. Google Cloud TCP proxy load balancers cannot listen
on 6443. However, GCP's load balancer can be made to listen on
443, while kube-apiserver uses 6443 across all platforms.
