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Co-authored-by: Joel Speed <Joel.speed@hotmail.co.uk>
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Danil-Grigorev and JoelSpeed committed Jul 14, 2021
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8 changes: 4 additions & 4 deletions enhancements/machine-api/out-of-tree-provider-support.md
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Expand Up @@ -334,10 +334,10 @@ Once the provider is moved to out-of-tree, the migration mechanism will be disab

#### Bootstrap changes

One of the responsibilities of the initialisation process for Kubelet is to set the `Node`’s IP addresses within the status of the `Node` object. The remaining responsibilities are not important for this document bar the removal of a taint which prevents workloads running on the `Node` until the initialisation has completed.
One of the responsibilities of the initialisation process for Kubelet is to set the `Node`’s IP addresses within the status of the `Node` object. The remaining responsibilities are not important for bootstrapping, bar the removal of a taint which prevents workloads running on the `Node` until the initialisation has completed.

A second part of the bootstrap process for a new `Node`, is to initialise the `CNI` (networking). Typically in an OpenShift cluster, this is handled once the Networking Operator starts.
The Networking operator will create the `CNI` pods (typically OpenShift SDN), which schedule on the `Node`, use the `Node` IP addresses to create a `HostSubnet` resource within Kubernetes and then mark then complete the initialisation process for the `CNI`, in doing so, marking the `Node` as ready and allowing the remaining workloads to start.
The Networking operator will create the `CNI` pods (typically OpenShift SDN), which schedule on the `Node`, use the `Node` IP addresses to create a `HostSubnet` resource within Kubernetes and then complete the initialisation process for the `CNI`, in doing so, marking the `Node` as ready and allowing the remaining workloads to start.

Before the `CNI` is initialized on a `Node`, in-cluster networking such as Service IPs, in particular the API server Service, will not work for any `Pod` on the `Node`. Additionally, any `Pod` that requires the Pod Networking implemented by `CNI`, cannot start.
For this reason, `Pods` such as the Networking Operator must use host networking and the “API Int” load balancer to contact the Kube API Server.
Expand All @@ -346,7 +346,7 @@ Because the `CCM` is taking over the responsibility of setting the `Node` IP add

To do so, we must tolerate the not-ready taint for these pods and they must all run with host networking and use the API load balancer, rather than using the internal Service. This will ensure that the cluster can bootstrap successfully and recover from any disaster recovery scenario.

Our operator will take precedence for CNI operator. It will tolerate `NotReady` `NoSchedule` taint and `CCM` specific `Uninitialized` taint. Operator would start as the first operator in the cluster when first `control-plane` is created, and be responsible for initializing `Nodes` which will allow latter operators to start.
Our operator will become a prerequisite for the Network Operator. CCCMO will tolerate the `Node` `NotReady:NoSchedule` and `CCM` specific `Uninitialized` taints. CCCMO will start as the first operator on the control plane hosts, and be responsible for initializing `Nodes`, allowing other operators to start.

#### Metrics

Expand Down Expand Up @@ -712,4 +712,4 @@ Mandatory operator repository:
- [The Kubernetes Cloud Controller Manager](https://medium.com/@m.json/the-kubernetes-cloud-controller-manager-d440af0d2be5) article
https://hackmd.io/00IoVWBiSVm8mMByxerTPA#
- [CSI support](https://github.com/openshift/enhancements/blob/master/enhancements/storage/csi-driver-install.md#ocp-45-kubernetes-118)
- [CCM role in bootstrap process](https://docs.google.com/document/d/1yAczhHNJ4rDqVFFvyi7AZ27DEQdvx8DmLNbavIjrjn0)
- [CCM role in bootstrap process](https://docs.google.com/document/d/1yAczhHNJ4rDqVFFvyi7AZ27DEQdvx8DmLNbavIjrjn0)

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