* On cloud platforms, `delete-node.service` tries to delete the
local node (not always possible depending on preemption time)
* Since v1.18.3, kubelet TLS bootstrap generates a kubeconfig
in `/var/lib/kubelet` which should be used with kubectl in
the delete-node oneshot
* Use docker to run the `kubelet.service` container
* Update Kubelet mounts to match Fedora CoreOS
* Remove unused `/etc/ssl/certs` mount (see
https://github.com/poseidon/typhoon/pull/810)
* Remove unused `/usr/share/ca-certificates` mount
* Remove `/etc/resolv.conf` mount, Docker default is ok
* Change `delete-node.service` to use docker instead of rkt
and inline ExecStart, as was done on Fedora CoreOS
* Fix permission denied on shutdown `delete-node`, caused
by the kubeconfig mount changing with the introduction of
node TLS bootstrap
Background
* podmand, rkt, and runc daemonless container process runners
provide advantages over the docker daemon for system containers.
Docker requires workarounds for use in systemd units where the
ExecStart must tail logs so systemd can monitor the daemonized
container. https://github.com/moby/moby/issues/6791
* Why switch then? On Flatcar Linux, podman isn't shipped. rkt
works, but isn't developing while container standards continue
to move forward. Typhoon has used runc for the Kubelet runner
before in Fedora Atomic, but its more low-level. So we're left
with Docker, which is less than ideal, but shipped in Flatcar
* Flatcar Linux appears to be shifting system components to
use docker, which does provide some limited guards against
breakages (e.g. Flatcar cannot enable docker live restore)
* Originally, poseidon/terraform-render-bootstrap generated
TLS certificates, manifests, and cluster "assets" written
to local disk (`asset_dir`) during terraform apply cluster
bootstrap
* Typhoon v1.17.0 introduced bootstrapping using only Terraform
state to store cluster assets, to avoid ever writing sensitive
materials to disk and improve automated use-cases. `asset_dir`
was changed to optional and defaulted to "" (no writes)
* Typhoon v1.18.0 deprecated the `asset_dir` variable, removed
docs, and announced it would be deleted in future.
* Add Terraform output `assets_dir` map
* Remove the `asset_dir` variable
Cluster assets are now stored in Terraform state only. For those
who wish to write those assets to local files, this is possible
doing so explicitly.
```
resource local_file "assets" {
for_each = module.yavin.assets_dist
filename = "some-assets/${each.key}"
content = each.value
}
```
Related:
* https://github.com/poseidon/typhoon/pull/595
* https://github.com/poseidon/typhoon/pull/678
* CoreOS Container Linux was deprecated in v1.18.3 (May 2020)
in favor of Fedora CoreOS and Flatcar Linux. CoreOS Container
Linux references were kept to give folks more time to migrate,
but AMIs have now been deleted. Time is up.
Rel: https://coreos.com/os/eol/
* seccomp graduated to GA in Kubernetes v1.19. Support for
seccomp alpha annotations will be removed in v1.22
* Replace seccomp annotations with the GA seccompProfile
field in the PodTemplate securityContext
* Switch profile from `docker/default` to `runtime/default`
(no effective change, since docker is the runtime)
* Verify with docker inspect SecurityOpt. Without the profile,
you'd see `seccomp=unconfined`
Related: https://github.com/poseidon/terraform-render-bootstrap/pull/215
* Fix race condition for bootstrap-secrets SELinux context on non-bootstrap controllers in multi-controller FCOS clusters
* On first boot from disk on non-bootstrap controllers, adding bootstrap-secrets races with kubelet.service starting, which can cause the secrets assets to have the wrong label until kubelet.service restarts (service, reboot, auto-update)
* This can manifest as `kube-apiserver`, `kube-controller-manager`, and `kube-scheduler` pods crashlooping on spare controllers on first cluster creation
* Fedora CoreOS now ships systemd-udev's `default.link` while
Flannel relies on being able to pick its own MAC address for
the `flannel.1` link for tunneled traffic to reach cni0 on
the destination side, without being dropped
* This change first appeared in FCOS testing-devel 32.20200624.20.1
and is the behavior going forward in FCOS since it was added
to align FCOS network naming / configs with the rest of Fedora
and address issues related to the default being missing
* Flatcar Linux (and Container Linux) has a specific flannel.link
configuration builtin, so it was not affected
* https://github.com/coreos/fedora-coreos-tracker/issues/574#issuecomment-665487296
Note: Typhoon's recommended and default CNI provider is Calico,
unless `networking` is set to flannel directly.
* Accept experimental CNI `networking` mode "cilium"
* Run Cilium v1.8.0-rc4 with overlay vxlan tunnels and a
minimal set of features. We're interested in:
* IPAM: Divide pod_cidr into /24 subnets per node
* CNI networking pod-to-pod, pod-to-external
* BPF masquerade
* NetworkPolicy as defined by Kubernetes (no L7 Policy)
* Continue using kube-proxy with Cilium probe mode
* Firewall changes:
* Require UDP 8472 for vxlan (Linux kernel default) between nodes
* Optional ICMP echo(8) between nodes for host reachability
(health)
* Optional TCP 4240 between nodes for endpoint reachability (health)
Known Issues:
* Containers with `hostPort` don't listen on all host addresses,
these workloads must use `hostNetwork` for now
https://github.com/cilium/cilium/issues/12116
* Erroneous warning on Fedora CoreOS
https://github.com/cilium/cilium/issues/10256
Note: This is experimental. It is not listed in docs and may be
changed or removed without a deprecation notice
Related:
* https://github.com/poseidon/terraform-render-bootstrap/pull/192
* https://github.com/cilium/cilium/issues/12217
* Fedora CoreOS `kubelet.service` can start before the hostname
is set. Kubelet reads the hostname to determine the node name to
register. If the hostname was read as localhost, Kubelet will
continue trying to register as localhost (problem)
* This race manifests as a node that appears NotReady, the Kubelet
is trying to register as localhost, while the host itself (by then)
has an AWS provided hostname. Restarting kubelet.service is a
manual fix so Kubelet re-reads the hostname
* This race could only be shown on AWS, not on Google Cloud or
Azure despite attempts. Bare-metal and DigitalOcean differ and
use hostname-override (e.g. afterburn) so they're not affected
* Wait for nodes to have a non-localhost hostname in the oneshot
that awaits /etc/resolve.conf. Typhoon has no valid cases for a
node hostname being localhost (not even single-node clusters)
Related Openshift: https://github.com/openshift/machine-config-operator/pull/1813
Close https://github.com/poseidon/typhoon/issues/765
* Remove node label `node.kubernetes.io/master` from controller nodes
* Use `node.kubernetes.io/controller` (present since v1.9.5,
[#160](https://github.com/poseidon/typhoon/pull/160)) to node select controllers
* Rename controller NoSchedule taint from `node-role.kubernetes.io/master` to
`node-role.kubernetes.io/controller`
* Tolerate the new taint name for workloads that may run on controller nodes
and stop tolerating `node-role.kubernetes.io/master` taint
* Kubelet `--lock-file` and `--exit-on-lock-contention` date
back to usage of bootkube and at one point running Kubelet
in a "self-hosted" style whereby an on-host Kubelet (rkt)
started pods, but then a Kubelet DaemonSet was scheduled
and able to take over (hence self-hosted). `lock-file` and
`exit-on-lock-contention` flags supported this pivot. The
pattern has been out of favor (in bootkube too) for years
because of dueling Kubelet complexity
* Typhoon runs Kubelet as a container via an on-host systemd
unit using podman (Fedora CoreOS) or rkt (Flatcar Linux). In
fact, Typhoon no longer uses bootkube or control plane pivot
(let alone Kubelet pivot) and uses static pods since v1.16.0
* https://github.com/poseidon/typhoon/pull/536
* Generated Kubelet TLS certificate and key are not longer
used or distributed to machines since Kubelet TLS bootstrap
is used instead. Remove the certificate and key from state
* Enable terraform-provider-ct `strict` mode for parsing
Container Linux Configs and snippets
* Fix Container Linux Config systemd unit syntax `enable`
(old) to `enabled`
* Align with Fedora CoreOS which uses strict mode already
* Build Kubelet container images internally and publish
to Quay and Dockerhub (new) as an alternative in case of
registry outage or breach
* Use our infra to provide single and multi-arch (default)
Kublet images for possible future use
* Docs: Show how to use alternative Kubelet images via
snippets and a systemd dropin (builds on #737)
Changes:
* Update docs with changes to Kubelet image building
* If you prefer to trust images built by Quay/Dockerhub,
automated image builds are still available with unique
tags (albeit with some limitations):
* Quay automated builds are tagged `build-{short_sha}`
(limit: only amd64)
* Dockerhub automated builts are tagged `build-{tag}`
and `build-master` (limit: only amd64, no shas)
Links:
* Kubelet: https://github.com/poseidon/kubelet
* Docs: https://typhoon.psdn.io/topics/security/#container-images
* Registries:
* quay.io/poseidon/kubelet
* docker.io/psdn/kubelet
* Write the systemd kubelet.service to use `KUBELET_IMAGE`
as the Kubelet. This provides a nice way to use systemd
dropins to temporarily override the image (e.g. during a
registry outage)
Note: Only Typhoon Kubelet images and registries are supported.
* Set a consistent MCS level/range for Calico install-cni
* Note: Rebooting a node was a workaround, because Kubelet
relabels /etc/kubernetes(/cni/net.d)
Background:
* On SELinux enforcing systems, the Calico CNI install-cni
container ran with default SELinux context and a random MCS
pair. install-cni places CNI configs by first creating a
temporary file and then moving them into place, which means
the file MCS categories depend on the containers SELinux
context.
* calico-node Pod restarts creates a new install-cni container
with a different MCS pair that cannot access the earlier
written file (it places configs every time), causing the
init container to error and calico-node to crash loop
* https://github.com/projectcalico/cni-plugin/issues/874
```
mv: inter-device move failed: '/calico.conf.tmp' to
'/host/etc/cni/net.d/10-calico.conflist'; unable to remove target:
Permission denied
Failed to mv files. This may be caused by selinux configuration on
the
host, or something else.
```
Note, this isn't a host SELinux configuration issue.
Related:
* https://github.com/poseidon/terraform-render-bootstrap/pull/186
* Enable bootstrap token authentication on kube-apiserver
* Generate the bootstrap.kubernetes.io/token Secret that
may be used as a bootstrap token
* Generate a bootstrap kubeconfig (with a bootstrap token)
to be securely distributed to nodes. Each Kubelet will use
the bootstrap kubeconfig to authenticate to kube-apiserver
as `system:bootstrappers` and send a node-unique CSR for
kube-controller-manager to automatically approve to issue
a Kubelet certificate and kubeconfig (expires in 72 hours)
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the `system:node-bootstrapper`
ClusterRole
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the csr nodeclient ClusterRole
* Add ClusterRoleBinding for bootstrap token subjects
(`system:bootstrappers`) to have the csr selfnodeclient ClusterRole
* Enable NodeRestriction admission controller to limit the
scope of Node or Pod objects a Kubelet can modify to those of
the node itself
* Ability for a Kubelet to delete its Node object is retained
as preemptible nodes or those in auto-scaling instance groups
need to be able to remove themselves on shutdown. This need
continues to have precedence over any risk of a node deleting
itself maliciously
Security notes:
1. Issued Kubelet certificates authenticate as user `system:node:NAME`
and group `system:nodes` and are limited in their authorization
to perform API operations by Node authorization and NodeRestriction
admission. Previously, a Kubelet's authorization was broader. This
is the primary security motivation.
2. The bootstrap kubeconfig credential has the same sensitivity
as the previous generated TLS client-certificate kubeconfig.
It must be distributed securely to nodes. Its compromise still
allows an attacker to obtain a Kubelet kubeconfig
3. Bootstrapping Kubelet kubeconfig's with a limited lifetime offers
a slight security improvement.
* An attacker who obtains the kubeconfig can likely obtain the
bootstrap kubeconfig as well, to obtain the ability to renew
their access
* A compromised bootstrap kubeconfig could plausibly be handled
by replacing the bootstrap token Secret, distributing the token
to new nodes, and expiration. Whereas a compromised TLS-client
certificate kubeconfig can't be revoked (no CRL). However,
replacing a bootstrap token can be impractical in real cluster
environments, so the limited lifetime is mostly a theoretical
benefit.
* Cluster CSR objects are visible via kubectl which is nice
4. Bootstrapping node-unique Kubelet kubeconfigs means Kubelet
clients have more identity information, which can improve the
utility of audits and future features
Rel: https://kubernetes.io/docs/reference/command-line-tools-reference/kubelet-tls-bootstrapping/
Rel: https://github.com/poseidon/terraform-render-bootstrap/pull/185
* Race: During initial bootstrap, static control plane pods
could hang with Permission denied to bootstrap secrets. A
manual fix involved restarting Kubelet, which relabeled mounts
The race had no effect on subsequent reboots.
* bootstrap.service runs podman with a private unshared mount
of /etc/kubernetes/bootstrap-secrets which uses an SELinux MCS
label with a category pair. However, bootstrap-secrets should
be shared as its mounted by Docker pods kube-apiserver,
kube-scheduler, and kube-controller-manager. Restarting Kubelet
was a manual fix because Kubelet relabels all /etc/kubernetes
* Fix bootstrap Pod to use the shared volume label, which leaves
bootstrap-secrets files with SELinux level s0 without MCS
* Also allow failed bootstrap.service to be re-applied. This was
missing on bare-metal and AWS
* In v1.18.0, kubectl apply would fail to apply manifests if any
single manifest was unable to validate. For example, if a CRD and
CR were defined in the same directory, apply would fail since the
CR would be invalid as the CRD wouldn't exist
* Typhoon temporary workaround was to separate CNI CRD manifests
and explicitly apply them first. No longer needed in v1.18.1+
* Kubernetes v1.18.1 restored the prior behavior where kubectl apply
applies as many valid manifests as it can. In the example above, the
CRD would be applied and the CR could be applied if the kubectl apply
was re-run (allowing for apply loops).
* Upstream fix: https://github.com/kubernetes/kubernetes/pull/89864
* No change to Fedora CoreOS modules
* For Container Linx AWS and Azure, change the `os_image` default
from coreos-stable to flatcar-stable
* For Container Linux GCP and DigitalOcean, change `os_image` to
be required since users should upload a Flatcar Linux image and
set the variable
* For Container Linux bare-metal, recommend users change the
`os_channel` to Flatcar Linux. No actual module change.
* Fix bootstrap error for missing `manifests-networking/crd*yaml`
when `networking = "flannel"`
* Cleanup manifest-networking directory left during bootstrap
* Regressed in v1.18.0 changes for Calico https://github.com/poseidon/typhoon/pull/675
* Change kube-proxy, flannel, and calico-node DaemonSet
tolerations to tolerate `node.kubernetes.io/not-ready`
and `node-role.kubernetes.io/master` (i.e. controllers)
explicitly, rather than tolerating all taints
* kube-system DaemonSets will no longer tolerate custom
node taints by default. Instead, custom node taints must
be enumerated to opt-in to scheduling/executing the
kube-system DaemonSets
* Consider setting the daemonset_tolerations variable
of terraform-render-bootstrap at a later date
Background: Tolerating all taints ruled out use-cases
where certain nodes might legitimately need to keep
kube-proxy or CNI networking disabled
Related: https://github.com/poseidon/terraform-render-bootstrap/pull/179
* Fix issue observed in us-east-1 where AMI filters chose the
latest testing channel release, rather than the stable chanel
* Fedora CoreOS AMI filter selects the latest image with a
matching name, x86_64, and hvm, excluding dev images. Add a
filter for "Fedora CoreOS stable", which seems to be the only
distinguishing metadata indicating the channel
* Fix delete-node service that runs on worker (cloud-only)
shutdown to delete a Kubernetes node. Regressed in #669
(unreleased)
* Use rkt `--exec` to invoke kubectl binary in the kubelet
image
* Use podman `--entrypoint` to invoke the kubectl binary in
the kubelet image
* Before Kubernetes v1.18.0, Kubelet only supported kubectl
`--limit-bytes` with the Docker `json-file` log driver so
the Fedora CoreOS default was overridden for conformance.
See https://github.com/poseidon/typhoon/pull/642
* Kubelet v1.18+ implemented support for other docker log
drivers, so the Fedora CoreOS default `journald` can be
used again
Rel: https://github.com/kubernetes/kubernetes/issues/86367
* Kubernetes plans to stop releasing the hyperkube container image
* Upstream will continue to publish `kube-apiserver`, `kube-controller-manager`,
`kube-scheduler`, and `kube-proxy` container images to `k8s.gcr.io`
* Upstream will publish Kubelet only as a binary for distros to package,
either as a DEB/RPM on traditional distros or a container image on
container-optimized operating systems
* Typhoon will package the upstream Kubelet (checksummed) and its
dependencies as a container image for use on CoreOS Container Linux,
Flatcar Linux, and Fedora CoreOS
* Update the Typhoon container image security policy to list
`quay.io/poseidon/kubelet`as an official distributed artifact
Hyperkube: https://github.com/kubernetes/kubernetes/pull/88676
Kubelet Container Image: https://github.com/poseidon/kubelet
Kubelet Quay Repo: https://quay.io/repository/poseidon/kubelet
* Quay has historically generated ACI signatures for images to
facilitate rkt's notions of verification (it allowed authors to
actually sign images, though `--trust-keys-from-https` is in use
since etcd and most authors don't sign images). OCI standardization
didn't adopt verification ideas and checking signatures has fallen
out of favor.
* Fix an issue where Quay no longer seems to be generating ACI
signatures for new images (e.g. quay.io/coreos/etcd:v.3.4.4)
* Don't be alarmed by rkt `--insecure-options=image`. It refers
to disabling image signature checking (i.e. docker pull doesn't
check signatures either)
* System containers for Kubelet and bootstrap have transitioned
to the docker:// transport, so there is precedent and this brings
all the system containers on Container Linux controllers into
alignment
* On clouds where workers can scale down or be preempted
(AWS, GCP, Azure), shutdown runs delete-node.service to
remove a node a prevent NotReady nodes from lingering
* Add the delete-node.service that wasn't carried over
from Container Linux and port it to use podman
* Allow users to extend the route table using a data reference
and adding route resources (e.g. unusual peering setups)
* Note: Internally connecting AWS clusters can reduce cross-cloud
flexibility and inhibits blue-green cluster patterns. It is not
recommended
* Add Terraform strip markers to consume beginning and
trailing whitespace in templated Kubelet arguments for
podman (Fedora CoreOS only)
* Fix initial `worker_node_labels` being quietly ignored
on Fedora CoreOS cloud platforms that offer the feature
* Close https://github.com/poseidon/typhoon/issues/650
* Fix the last minor issue for Fedora CoreOS clusters to pass CNCF's
Kubernetes conformance tests
* Kubelet supports a seldom used feature `kubectl logs --limit-bytes=N`
to trim a log stream to a desired length. Kubelet handles this in the
CRI driver. The Kubelet docker shim only supports the limit bytes
feature when Docker is configured with the default `json-file` logging
driver
* CNCF conformance tests started requiring limit-bytes be supported,
indirectly forcing the log driver choice until either the Kubelet or
the conformance tests are fixed
* Fedora CoreOS defaults Docker to use `journald` (desired). For now,
as a workaround to offer conformant clusters, the log driver can
be set back to `json-file`. RHEL CoreOS likely won't have noticed the
non-conformance since its using crio runtime
* https://github.com/kubernetes/kubernetes/issues/86367
Note: When upstream has a fix, the aim is to drop the docker config
override and use the journald default
* Select the most recent fedora-coreos-31 AMI on AWS, instead
of the most recent fedora-coreos-30 AMI (Nov 27, 2019)
* Evaluated with fedora-coreos-31.20200108.2.0-hvm
* Configure kube-proxy --metrics-bind-address=0.0.0.0 (default
127.0.0.1) to serve metrics on 0.0.0.0:10249
* Add firewall rules to allow Prometheus (resides on a worker) to
scrape kube-proxy service endpoints on controllers or workers
* Add a clusterIP: None service for kube-proxy endpoint discovery
* Change kubelet.service on Container Linux nodes to ExecStart Kubelet
inline to replace the use of the host OS kubelet-wrapper script
* Express rkt run flags and volume mounts in a clear, uniform way to
make the Kubelet service easier to audit, manage, and understand
* Eliminate reliance on a Container Linux kubelet-wrapper script
* Typhoon for Fedora CoreOS developed a kubelet.service that similarly
uses an inline ExecStart (except with podman instead of rkt) and a
more minimal set of volume mounts. Adopt the volume improvements:
* Change Kubelet /etc/kubernetes volume to read-only
* Change Kubelet /etc/resolv.conf volume to read-only
* Remove unneeded /var/lib/cni volume mount
Background:
* kubelet-wrapper was added in CoreOS around the time of Kubernetes v1.0
to simplify running a CoreOS-built hyperkube ACI image via rkt-fly. The
script defaults are no longer ideal (e.g. rkt's notion of trust dates
back to quay.io ACI image serving and signing, which informed the OCI
standard images we use today, though they still lack rkt's signing ideas).
* Shipping kubelet-wrapper was regretted at CoreOS, but remains in the
distro for compatibility. The script is not updated to track hyperkube
changes, but it is stable and kubelet.env overrides bridge most gaps
* Typhoon Container Linux nodes have used kubelet-wrapper to rkt/rkt-fly
run the Kubelet via the official k8s.gcr.io hyperkube image using overrides
(new image registry, new image format, restart handling, new mounts, new
entrypoint in v1.17).
* Observation: Most of what it takes to run a Kubelet container is defined
in Typhoon, not in kubelet-wrapper. The wrapper's value is now undermined
by having to workaround its dated defaults. Typhoon may be better served
defining Kubelet.service explicitly
* Typhoon for Fedora CoreOS developed a kubelet.service without the use
of a host OS kubelet-wrapper which is both clearer and eliminated some
volume mounts
* Rename Container Linux Config (CLC) files to *.yaml to align
with Fedora CoreOS Config (FCC) files and for syntax highlighting
* Replace common uses of Terraform `element` (which wraps around)
with `list[index]` syntax to surface index errors
* 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
* Detect the most recent Fedora CoreOS AMI to allow usage
of Fedora CoreOS in supported regions (previously just
us-east-1)
* Unpin the Fedora CoreOS AMI image which was pinned to
images that had been checked. This does mean if Fedora
publishes a broken image, it will be selected
* Filter out "dev" images which have similar naming
* 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)
* 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)
* 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)
* 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 newly minted "Fedora CoreOS Preview" AMI
* Remove iscsi, kubelet.path activation, and kubeconfig
distribution
* As usual, bare-metal efforts make cloud provider ports
much easier
* 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.
* For Container Linux or Flatcar Linux alpha/beta/stable,
continue using the `cgroupfs` driver
* For Fedora Atomic, continue using the `systemd` driver
* For Flatcar Linux Edge, use the `systemd` driver
* Replace v0.11 bracket type hints with Terraform v0.12 list expressions
* Use expression syntax instead of interpolated strings, where suggested
* Update AWS tutorial and worker pools documentation
* Define Terraform and plugin version requirements in versions.tf
* Require aws ~> 2.7 to support Terraform v0.12
* Require ct ~> 0.3.2 to support Terraform v0.12
* This change affects users who use worker pools on AWS, GCP, or
Azure with a Container Linux derivative
* Rename worker pool modules' `count` variable to `worker_count`,
because `count` will be a reserved variable name in Terraform v0.12
* Fix to remove a trailing slash that was erroneously introduced
in the scripting that updated from v1.14.1 to v1.14.2
* Workaround before this fix was to re-run `terraform init`
* Change flannel port from the kernel default 8472 to the
IANA assigned VXLAN port 4789
* Update firewall rules or security groups for VXLAN
* Why now? Calico now offers its own VXLAN backend so
standardizing on the IANA port will simplify config
* https://github.com/coreos/flannel/blob/master/Documentation/backends.md#vxlan
* Add an `enable_aggregation` variable to enable the kube-apiserver
aggregation layer for adding extension apiservers to clusters
* Aggregation is **disabled** by default. Typhoon recommends you not
enable aggregation. Consider whether less invasive ways to achieve your
goals are possible and whether those goals are well-founded
* Enabling aggregation and extension apiservers increases the attack
surface of a cluster and makes extensions a part of the control plane.
Admins must scrutinize and trust any extension apiserver used.
* Passing a v1.14 CNCF conformance test requires aggregation be enabled.
Having an option for aggregation keeps compliance, but retains the
stricter security posture on default clusters
* Add ability to load balance TCP applications (e.g. NodePort)
* Output the network load balancer ARN as `nlb_id`
* Accept a `worker_target_groups` (ARN) list to which worker
instances should be added
* AWS NLBs and target groups don't support UDP
* Add calico-ipam CRDs and RBAC permissions
* Switch IPAM from host-local to calico-ipam
* `calico-ipam` subnets `ippools` (defaults to pod CIDR) into
`ipamblocks` (defaults to /26, but set to /24 in Typhoon)
* `host-local` subnets the pod CIDR based on the node PodCIDR
field (set via kube-controller-manager as /24's)
* Create a custom default IPv4 IPPool to ensure the block size
is kept at /24 to allow 110 pods per node (Kubernetes default)
* Retaining host-local was slightly preferred, but Calico v3.6
is migrating all usage to calico-ipam. The codepath that skipped
calico-ipam for KDD was removed
* https://docs.projectcalico.org/v3.6/release-notes/
* Allow terraform-provider-aws >= v1.13, but < 3.0. No change
to the minimum version, but allow using v2.x.y releases
* Verify compatability with terraform-provider-aws v2.1.0
* Resolve in-addr.arpa and ip6.arpa DNS PTR requests for Kubernetes
service IPs and pod IPs
* Previously, CoreDNS was configured to resolve in-addr.arpa PTR
records for service IPs (but not pod IPs)
* Assign pod priorityClassNames to critical cluster and node
components (higher is higher priority) to inform node out-of-resource
eviction order and scheduler preemption and scheduling order
* Priority Admission Controller has been enabled since Typhoon
v1.11.1
* Fix a regression caused by lowering the Kubelet TLS client
certificate to system:nodes group (#100) since dropping
cluster-admin dropped the Kubelet's ability to delete nodes.
* On clouds where workers can scale down (manual terraform apply,
AWS spot termination, Azure low priority deletion), worker shutdown
runs the delete-node.service to remove a node to prevent NotReady
nodes from accumulating
* Allow Kubelets to delete cluster nodes via system:nodes group. Kubelets
acting with system:node and kubelet-delete ClusterRoles is still an
improvement over acting as cluster-admin
* DNS zones served by AWS Route53 may use AWS's special alias records
(other DNS providers would use a CNAME) to resolve the ingress NLB.
Alias records require the NLB DNS name's DNS zone id (not the cluster
`dns_zone_id`)
* System components that require certificates signed by the cluster
CA can submit a CSR to the apiserver, have an administrator inspect
and approve it, and be issued a certificate
* Configure kube-controller-manager to sign Approved CSR's using the
cluster CA private key
* Admins are responsible for approving or denying CSRs, otherwise,
no certificate is issued. Read the Kubernetes docs carefully and
verify the entity making the request and the authorization level
* https://kubernetes.io/docs/tasks/tls/managing-tls-in-a-cluster
* Use a single admin kubeconfig for initial bootkube bootstrap
and for use by a human admin. Previously, an admin kubeconfig
without a named context was used for bootstrap and direct usage
with KUBECONFIG=path, while one with a named context was used
for `kubectl config use-context` style usage. Confusing.
* Provide the admin kubeconfig via `assets/auth/kubeconfig`,
`assets/auth/CLUSTER-config`, or output `kubeconfig-admin`
* terraform-render-bootkube module deprecated kube_dns_service_ip
output in favor of cluster_dns_service_ip
* Rename k8s_dns_service_ip to cluster_dns_service_ip for
consistency too
* Kubelets can use a lower-privilege TLS client certificate with
Org system:nodes and a binding to the system:node ClusterRole
* Admin kubeconfig's continue to belong to Org system:masters to
provide cluster-admin (available in assets/auth/kubeconfig or as
a Terraform output kubeconfig-admin)
* Remove bare-metal output variable kubeconfig
* Add ServiceAccounts and ClusterRoleBindings for kube-apiserver
and kube-scheduler
* Remove the ClusterRoleBinding for the kube-system default ServiceAccount
* Rename the CA certificate CommonName for consistency with upstream
* T3 is the next generation general purpose burstable
instance type. Compared with t2.small, the t3.small is
cheaper, has 2 vCPU (instead of 1) and provides 5 Gbps
of pod-to-pod bandwidth (instead of 1 Gbps)
* Add kube-router for pod networking and NetworkPolicy
as an experiment
* Experiments are not documented or supported in any way,
and may be removed without notice. They have known issues
and aren't enabled without special options.
* Remove bullet about isolating workloads on workers, its
now common practice and new users will assume it
* List advanced features available in each module
* Fix erroneous Kubernetes version listing for Google Cloud
Fedora Atomic
* Calico Felix has been reporting anonymous usage data about the
version and cluster size, which violates Typhoon's privacy policy
where analytics should be opt-in only
* Add a variable enable_reporting (default: false) to allow opting
in to reporting usage data to Calico (or future components)
* loop sends an initial query to detect infinite forwarding
loops in configured upstream DNS servers and fast exit with
an error (its a fatal misconfiguration on the network that
will otherwise cause resolvers to consume memory/CPU until
crashing, masking the problem)
* https://github.com/coredns/coredns/tree/master/plugin/loop
* loadbalance randomizes the ordering of A, AAAA, and MX records
in responses to provide round-robin load balancing (as usual,
clients may still cache responses though)
* https://github.com/coredns/coredns/tree/master/plugin/loadbalance
* Prefer InternalIP and ExternalIP over the node's hostname,
to match upstream behavior and kubeadm
* Previously, hostname-override was used to set node names
to internal IP's to work around some cloud providers not
resolving hostnames for instances (e.g. DO droplets)
* Updating the `terraform-provider-ct` plugin is known to produce
a `user_data` diff in all pre-existing clusters. Applying the
diff to pre-existing cluster destroys controller nodes
* Ignore changes to controller `user_data`. Once all managed
clusters use a release containing this change, it is possible
to update the `terraform-provider-ct` plugin (worker `user_data`
will still be modified)
* Changing the module `ref` for an existing cluster and
re-applying is still NOT supported (although this PR
would protect controllers from being destroyed)
* Run at least two replicas of CoreDNS to better support
rolling updates (previously, kube-dns had a pod nanny)
* On multi-master clusters, set the CoreDNS replica count
to match the number of masters (e.g. a 3-master cluster
previously used replicas:1, now replicas:3)
* Add AntiAffinity preferred rule to favor distributing
CoreDNS pods across controller nodes nodes
* Continue to ensure scheduler and controller-manager run
at least two replicas to support performing kubectl edits
on single-master clusters (no change)
* For multi-master clusters, set scheduler / controller-manager
replica count to the number of masters (e.g. a 3-master cluster
previously used replicas:2, now replicas:3)
* Add new bird and felix readiness checks
* Read MTU from ConfigMap veth_mtu
* Add RBAC read for serviceaccounts
* Remove invalid description from CRDs
* Release v1.11.1 erroneously left Fedora Atomic clusters using
the v1.11.0 Kubelet. The rest of the control plane ran v1.11.1
as expected
* Update Kubelet from v1.11.0 to v1.11.1 so Fedora Atomic matches
Container Linux
* Container Linux modules were not affected
* Basic monitoring (free) is sufficient for casual console browsing
* Detailed monitoring (paid) is not leveraged for CloudWatch anyway
* Favor Prometheus for cloud-agnostic metrics, aggregation, and alerting
* Simplify clusters to come with a single NLB
* Listen for apiserver traffic on port 6443 and forward
to controllers (with healthy apiserver)
* Listen for ingress traffic on ports 80/443 and forward
to workers (with healthy ingress controller)
* Reduce cost of default clusters by 1 NLB ($18.14/month)
* Keep using CNAME records to the `ingress_dns_name` NLB and
the nginx-ingress addon for Ingress (up to a few million RPS)
* Users with heavy traffic (many million RPS) can create their
own separate NLB(s) for Ingress and use the new output worker
target groups
* Fix issue where additional worker pools come with an
extraneous network load balancer
Dalton Hubble
Bo Huang
Ben Drucker
Suraj Deshmukh
Valer Cara
Jordan Pittier
Tamer Fahmy
Robert Fairburn