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Add --feature-gates flag to support scale up on volume limits (CSI migration enabled) #4539

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Dec 20, 2021
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Add --feature-gates flag to support scale up on volume limits (CSI migration enabled) #4539

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13 changes: 13 additions & 0 deletions cluster-autoscaler/FAQ.md
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Original file line number Diff line number Diff line change
Expand Up @@ -33,6 +33,7 @@ this document:
* [How can I prevent Cluster Autoscaler from scaling down a particular node?](#how-can-i-prevent-cluster-autoscaler-from-scaling-down-a-particular-node)
* [How can I configure overprovisioning with Cluster Autoscaler?](#how-can-i-configure-overprovisioning-with-cluster-autoscaler)
* [How can I enable/disable eviction for a specific DaemonSet](#how-can-i-enabledisable-eviction-for-a-specific-daemonset)
* [How can I enable Cluster Autoscaler to scale up when Node's max volume count is exceeded (CSI migration enabled)?](#how-can-i-enable-cluster-autoscaler-to-scale-up-when-nodes-max-volume-count-is-exceeded-csi-migration-enabled)
* [Internals](#internals)
* [Are all of the mentioned heuristics and timings final?](#are-all-of-the-mentioned-heuristics-and-timings-final)
* [How does scale-up work?](#how-does-scale-up-work)
Expand Down Expand Up @@ -459,6 +460,17 @@ sufficient to modify the pod spec in the DaemonSet object.

This annotation has no effect on pods that are not a part of any DaemonSet.

### How can I enable Cluster Autoscaler to scale up when Node's max volume count is exceeded (CSI migration enabled)?

Kubernetes scheduler will fail to schedule a Pod to a Node if the Node's max volume count is exceeded. In such case to enable Cluster Autoscaler to scale up in a Kubernetes cluster with [CSI migration](https://github.com/kubernetes/enhancements/blob/master/keps/sig-storage/625-csi-migration/README.md) enabled, the appropriate CSI related feature gates have to be specified for the Cluster Autoscaler (if the corresponding feature gates are not enabled by default).

For example:
```
--feature-gates=CSIMigration=true,CSIMigration{Provdider}=true,InTreePlugin{Provider}Unregister=true
```

For a complete list of the feature gates and their default values per Kubernetes versions, refer to the [Feature Gates documentation](https://kubernetes.io/docs/reference/command-line-tools-reference/feature-gates/).

****************

# Internals
Expand Down Expand Up @@ -735,6 +747,7 @@ The following startup parameters are supported for cluster autoscaler:
| `min-replica-count` | Minimum number or replicas that a replica set or replication controller should have to allow their pods deletion in scale down | 0
| `daemonset-eviction-for-empty-nodes` | Whether DaemonSet pods will be gracefully terminated from empty nodes | false
| `daemonset-eviction-for-occupied-nodes` | Whether DaemonSet pods will be gracefully terminated from non-empty nodes | true
| `feature-gates` | A set of key=value pairs that describe feature gates for alpha/experimental features. | ""

# Troubleshooting:

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3 changes: 3 additions & 0 deletions cluster-autoscaler/main.go
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Expand Up @@ -34,6 +34,7 @@ import (
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apiserver/pkg/server/mux"
"k8s.io/apiserver/pkg/server/routes"
utilfeature "k8s.io/apiserver/pkg/util/feature"
"k8s.io/autoscaler/cluster-autoscaler/cloudprovider"
cloudBuilder "k8s.io/autoscaler/cluster-autoscaler/cloudprovider/builder"
"k8s.io/autoscaler/cluster-autoscaler/config"
Expand Down Expand Up @@ -392,7 +393,9 @@ func main() {
leaderElection.LeaderElect = true

options.BindLeaderElectionFlags(&leaderElection, pflag.CommandLine)
utilfeature.DefaultMutableFeatureGate.AddFlag(pflag.CommandLine)
kube_flag.InitFlags()

healthCheck := metrics.NewHealthCheck(*maxInactivityTimeFlag, *maxFailingTimeFlag)

klog.V(1).Infof("Cluster Autoscaler %s", version.ClusterAutoscalerVersion)
Expand Down