* To accompany the restructure of the bare-metal modules to
allow discrete workers to be defined and attached to a cluster
(#1295), the `workers` variable (older way, used for defining
homogeneous workers inline) should be optional and default
to an empty list
* Add docs covering inline vs discrete metal workers
Fix#1301
* Add an internal `worker` module to the bare-metal module, to
allow individual bare-metal machines to be defined and joined
to an existing bare-metal cluster. This is similar to the "worker
pools" modules for adding sets of nodes to cloud (AWS, GCP, Azure)
clusters, but on metal, each piece of hardware is potentially
unique
New: Using the new `worker` module, a Kubernetes cluster can be defined
without any `workers` (i.e. just a control-plane). Use the `worker`
module to define each piece machine that should join the bare-metal
cluster and customize it in detail. This style is quite flexible and
suited for clusters with hardware that varies quite a bit.
```tf
module "mercury" {
source = "git::https://github.com/poseidon/typhoon//bare-metal/flatcar-linux/kubernetes?ref=v1.26.2"
# bare-metal
cluster_name = "mercury"
matchbox_http_endpoint = "http://matchbox.example.com"
os_channel = "flatcar-stable"
os_version = "2345.3.1"
# configuration
k8s_domain_name = "node1.example.com"
ssh_authorized_key = "ssh-rsa AAAAB3Nz..."
# machines
controllers = [{
name = "node1"
mac = "52:54:00:a1:9c:ae"
domain = "node1.example.com"
}]
}
```
```tf
module "mercury-node1" {
source = "git::https://github.com/poseidon/typhoon//bare-metal/flatcar-linux/kubernetes/worker?ref=v1.26.2"
cluster_name = "mercury"
# bare-metal
matchbox_http_endpoint = "http://matchbox.example.com"
os_channel = "flatcar-stable"
os_version = "2345.3.1"
# configuration
name = "node2"
mac = "52:54:00:b2:2f:86"
domain = "node2.example.com"
kubeconfig = module.mercury.kubeconfig
ssh_authorized_key = "ssh-rsa AAAAB3Nz..."
# optional
snippets = []
node_labels = []
node_tains = []
install_disk = "/dev/vda"
cached_install = false
}
```
For clusters with fairly similar hardware, you may continue to
define `workers` directly within the cluster definition. This
reduces some repetition, but is not quite as flexible.
```tf
module "mercury" {
source = "git::https://github.com/poseidon/typhoon//bare-metal/flatcar-linux/kubernetes?ref=v1.26.1"
# bare-metal
cluster_name = "mercury"
matchbox_http_endpoint = "http://matchbox.example.com"
os_channel = "flatcar-stable"
os_version = "2345.3.1"
# configuration
k8s_domain_name = "node1.example.com"
ssh_authorized_key = "ssh-rsa AAAAB3Nz..."
# machines
controllers = [{
name = "node1"
mac = "52:54:00:a1:9c:ae"
domain = "node1.example.com"
}]
workers = [
{
name = "node2",
mac = "52:54:00:b2:2f:86"
domain = "node2.example.com"
},
{
name = "node3",
mac = "52:54:00:c3:61:77"
domain = "node3.example.com"
}
]
}
```
Optional variables `snippets`, `worker_node_labels`, and
`worker_node_taints` are still defined as a map from machine name
to a list of snippets, labels, or taints respectively to allow some
degree of per-machine customization. However, fields like
`install_disk`, `kernel_args`, `cached_install` and future options
will not be designed this way. Instead, if your machines vary it
is recommended to use the new `worker` module to define each node
* Terraform supports sourcing modules from either Git repos or from
their own hosted Terraform Module Registry, introduced a few years ago
* Typhoon docs have always shown using Git-based module sources, not
the Terraform Module Registry. For example, module usage should be
`source = "git::https://github.com/poseidon/typhoon/...` not
`source = poseidon/kubernetes/...`
* Typhoon published Flatcar Linux modules (CoreOS Container Linux at the time)
to Terraform Module Registry, but the approach has a number of drawbacks
for publishers and for users.
* Terraform's Module Registry requires subtree mirroring Typhoon to special
terraform-platform-kubernetes repos. This distorts Git history,
requires special automation, and the registry's naming requirements
don't allow us to publish our full matrix of modules (Fedora CoreOS
and Flatcar Linux, across AWS, Azure, GCP, on-prem, and DigitalOcean)
* Terraform's Module Registry only supports release versions (no commit SHAs
or forks)
* Ultimately, the Terraform Module Registry limits user flexibility, has
tedious publishing constraints, and introduces centralization where the
current decentralized Git-based approach is simpler and more featureful
Note: This does not affect Terraform _Providers_ like `poseidon/matchbox`
or `poseidon/ct`. For Terraform providers, Terraform's centralized
platform eases provider plugin installation and provides value
* @typhoon@fosstodon.org will announce Typhoon releases, like the
@typhoon8s Twitter account does today
* @poseidon@fosstodon.org will announce Poseidon Labs news and
general projects, like the @poseidonlabs Twitter account does today
* Kubelet GracefulNodeShutdown works, but only partially handles
gracefully stopping the Kubelet. The most noticeable drawback
is that Completed Pods are left around
* Use a project like poseidon/scuttle or a similar systemd unit
as a snippet to add drain and/or delete behaviors if desired
* This reverts commit 1786e34f33.
Rel:
* https://www.psdn.io/posts/kubelet-graceful-shutdown/
* https://github.com/poseidon/scuttle
* delete-node.service used to be used to remove nodes from the
cluster on shutdown, but its long since it last worked properly
* If there is still a desire for this concept, it can be added
with a custom snippet and with a better systemd unit
* network.target is a passive unit that's not actually pulled
in by units requiring or wanting it, its only used for shutdown
ordering
> "Services using the network should ... avoid any Wants=network.target or even Requires=network.target"
Rel: https://www.freedesktop.org/wiki/Software/systemd/NetworkTarget/
