Add option for passing extended resources in node labels in GKE

[mu-soliman]

/kind feature

What this PR does / why we need it:

on GKE, Cluster atuoscaler reads extended resource information from kubenv->AUTOSCALER_ENV_VARS->extended_resources in the managed scaling group template definition.

However, users have no way to add a variable to extended_resources, they are controlled from GKE side. This results in cluster autoscaler not knowing about extended resources and in return not supporting scale up from zero for all node pools that have extended resources (like GPU) on GKE.

On the other hand, node labels are passed from the node pool to the managed scaling group template through the kubenv->AUTOSCALER_ENV_VARS->node_labels.

This commit introduces the ability to pass extended resources to the cluster autoscaler as node labels with defined prefix on GKE, similar to how cluster autoscaler expects extended resources on AWS. This allows scaling from zero for node pools with extended resrouces.

on GKE, Adding node labels that start with "clusterautoscaler-nodetemplate-resources-", with value equal to the amount of the resources, allows the cluster autoscaler to detect extended resources and scale up the node pools from zero. 

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: mu-soliman / name: Muhammad Soliman (2b62a7d, dd6f11b)

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[whisperity]

However, users have no way to add a variable to extended_resources, they are controlled from GKE side. This results in cluster autoscaler not knowing about extended resources and in return not supporting scale up from zero for all node pools that have extended resources (like GPU) on GCE.

So is this for GKE (cloud-managed Kubernetes) or GCE (virtual machines with self-managed Kubernetes)? I am asking because I am having troubles with scaling-up from 0 and looking into ways, but for me the kubelets are all self-installed, and I have no idea where the KUBE_ENV could be set.

[mu-soliman]

However, users have no way to add a variable to extended_resources, they are controlled from GKE side. This results in cluster autoscaler not knowing about extended resources and in return not supporting scale up from zero for all node pools that have extended resources (like GPU) on GCE.

So is this for GKE (cloud-managed Kubernetes) or GCE (virtual machines with self-managed Kubernetes)? I am asking because I am having troubles with scaling-up from 0 and looking into ways, but for me the kubelets are all self-installed, and I have no idea where the KUBE_ENV could be set.

On GKE cluster autoscaler is configured with cloudProvider parameter set to the value gce, I don't know why, probably for historic reasons, but the code change was done uder GCE subdirectory. The same cluster autoscaler code runs for both GKE and GCE.

The change I submitted was tested on GKE, so I updated the description and title to mention GKE, but I expect that it will run on GCE.

[whisperity]

The change I submitted was tested on GKE, so I updated the description and title to mention GKE, but I expect that it will run on GCE.

@mu-soliman For reference, I found out that in case someone like me uses "pure" GCE, setting kube-env under the VM's Metadata: information it is possible to simulate the GKE behaviour (such as providing these extended resource flags). Which was nothing sort of a godsend that spared me of days of developing a patch related to it.