* Consolidate load balancer frontend IPs to just the minimal IPv4
and IPv6 addresses that are needed per load balancer. apiserver and
ingress use separate ports, so there is not a true need for a separate
public IPv4 address just for apiserver
* Some might prefer a separate IP just because it slightly hides the
apiserver, but these are public hosted endpoints that can be discovered
* Reduce the cost of an Azure cluster since IPv4 public IPs are billed
($3.60/mo/cluster)
* Rename the region variable to location to align with Azure
platform conventions, where resources are created within an
Azure location, which are themselves part of broader geographical
regions
* Define a dual-stack virtual network with both IPv4 and IPv6 private
address space. Change `host_cidr` variable (string) to a `network_cidr`
variable (object) with "ipv4" and "ipv6" fields that list CIDR strings.
* Define dual-stack controller and worker subnets. Disable Azure
default outbound access (a deprecated fallback mechanism)
* Enable dual-stack load balancing to Kubernetes Ingress by adding
a public IPv6 frontend IP and LB rule to the load balancer.
* Enable worker outbound IPv6 connectivity through load balancer
SNAT by adding an IPv6 frontend IP and outbound rule
* Configure controller nodes with a public IPv6 address to provide
direct outbound IPv6 connectivity
* Add an IPv6 worker backend pool. Azure requires separate IPv4 and
IPv6 backend pools, though the health probe can be shared
* Extend network security group rules for IPv6 source/destinations
Checklist:
Access to controller and worker nodes via IPv6 addresses:
* SSH access to controller nodes via public IPv6 address
* SSH access to worker nodes via (private) IPv6 address (via
controller)
Outbound IPv6 connectivity from controller and worker nodes:
```
nc -6 -zv ipv6.google.com 80
Ncat: Version 7.94 ( https://nmap.org/ncat )
Ncat: Connected to [2607:f8b0:4001:c16::66]:80.
Ncat: 0 bytes sent, 0 bytes received in 0.02 seconds.
```
Serve Ingress traffic via IPv4 or IPv6 just requires setting
up A and AAAA records and running the ingress controller with
`hostNetwork: true` since, hostPort only forwards IPv4 traffic
* Allow passing a dummy RSA key to Azure to satisfy its obtuse
requirements (recommend deleting the corresponding private key)
* Then `ssh_authorized_key` can be used to provide Fedora CoreOS
or Flatcar Linux with a modern ed25519 public key to set in the
authorized_keys via Ignition
* When invalid Ignition snippets are provided to Typhoon, it
can be useful to view Azure's boot logs for the instance, which
requires boot diagnostics be enabled
* Kinvolk now publishes Flatcar Linux images for ARM64
* For now, amd64 image must specify a plan while arm64 images
must NOT specify a plan due to how Kinvolk publishes.
Rel: https://github.com/flatcar/Flatcar/issues/872
* Switch from Azure Hypervisor generation 1 to generation 2
* Change default Azure `worker_type` from Standard_DS1_v2 to Standard_D2as_v5
* Get 2 VCPU, 7 GiB, 12500Mbps (vs 1 VCPU, 3.5GiB, 750 Mbps)
* Small increase in pay-as-you-go price ($53.29 -> $62.78)
* Small increase in spot price ($5.64/mo -> $7.37/mo)
* Change from Intel to AMD EPYC (`D2as_v5` cheaper than `D2s_v5`)
Notes: Azure makes you accept terms for each plan:
```
az vm image terms accept --publish kinvolk --offer flatcar-container-linux-free --plan stable-gen2
```
Rel:
* https://learn.microsoft.com/en-us/azure/virtual-machines/dasv5-dadsv5-series#dasv5-series
* https://learn.microsoft.com/en-us/azure/virtual-machines/dv2-dsv2-series#dsv2-series
* Requires poseidon v0.11+ and Flatcar Linux 3185.0.0+ (action required)
* Previously, Flatcar Linux configs have been parsed as Container
Linux Configs to Ignition v2.2.0 specs by poseidon/ct
* Flatcar Linux starting in 3185.0.0 now supports Ignition v3.x specs
(which are rendered from Butane Configs, like Fedora CoreOS)
* poseidon/ct v0.11.0 adds support for the flatcar Butane Config
variant so that Flatcar Linux can use Ignition v3.x
Rel:
* [Flatcar Support](https://flatcar-linux.org/docs/latest/provisioning/ignition/specification/#ignition-v3)
* [poseidon/ct support](https://github.com/poseidon/terraform-provider-ct/pull/131)
* Flatcar Linux has not published an Edge channel image since
April 2020 and recently removed mention of the channel from
their documentation https://github.com/kinvolk/Flatcar/pull/345
* Users of Flatcar Linux Edge should move to the stable, beta, or
alpha channel, barring any alternate advice from upstream Flatcar
Linux
* CoreOS Container Linux was deprecated in v1.18.3
* Continue transitioning docs and modules from supporting
both CoreOS and Flatcar "variants" of Container Linux to
now supporting Flatcar Linux and equivalents
Action Required: Update the Flatcar Linux modules `source`
to replace `s/container-linux/flatcar-linux`. See docs for
examples
