* Original tutorials favored including the platform (e.g.
google-cloud) in modules (e.g. google-cloud-yavin). Prefer
naming conventions where each module / cluster has a simple
name (e.g. yavin) since the platform is usually redundant
* Retain the example cluster naming themes per platform
* Allow generated assets (TLS materials, manifests) to be
securely distributed to controller node(s) via file provisioner
(i.e. ssh-agent) as an assets bundle file, rather than relying
on assets being locally rendered to disk in an asset_dir and
then securely distributed
* Change `asset_dir` from required to optional. Left unset,
asset_dir defaults to "" and no assets will be written to
files on the machine that runs terraform apply
* Enhancement: Managed cluster assets are kept only in Terraform
state, which supports different backends (GCS, S3, etcd, etc) and
optional encryption. terraform apply accesses state, runs in-memory,
and distributes sensitive materials to controllers without making
use of local disk (simplifies use in CI systems)
* Enhancement: Improve asset unpack and layout process to position
etcd certificates and control plane certificates more cleanly,
without unneeded secret materials
Details:
* Terraform file provisioner support for distributing directories of
contents (with unknown structure) has been limited to reading from a
local directory, meaning local writes to asset_dir were required.
https://github.com/poseidon/typhoon/issues/585 discusses the problem
and newer or upcoming Terraform features that might help.
* Observation: Terraform provisioner support for single files works
well, but iteration isn't viable. We're also constrained to Terraform
language features on the apply side (no extra plugins, no shelling out)
and CoreOS / Fedora tools on the receive side.
* Take a map representation of the contents that would have been splayed
out in asset_dir and pack/encode them into a single file format devised
for easy unpacking. Use an awk one-liner on the receive side to unpack.
In pratice, this has worked well and its rather nice that a single
assets file is transferred by file provisioner (all or none)
Rel: https://github.com/poseidon/terraform-render-bootstrap/pull/162
* 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
* Review variables available in AWS kubernetes and workers
modules and documentation
* Switching between spot and on-demand has worked since
Terraform v0.12
* Generally, there are too many knobs. Less useful ones
should be de-emphasized or removed
* Remove `cluster_domain_suffix` documentation
* Document worker pools `node_labels` variable to set the
initial node labels for a homogeneous set of workers
* Document `worker_node_labels` convenience variable to
set the initial node labels for default worker nodes
* 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)
* terraform-provider-aws v2.23.0 allows AWS root block devices
to enable encryption by default.
* Require updating terraform-provider-aws to v2.23.0 or higher
* Enable root EBS device encryption by default for controller
instances and worker instances in auto-scaling groups
For comparison:
* Google Cloud persistent disks have been encrypted by
default for years
* Azure managed disk encryption is not ready yet (#486)
* 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.
Dalton Hubble
Valer Cara