CoreDNS early scale down to 1 replica

[prezha]

fixes #10655

this pr proposes to scale down the number of CoreDNS replica to 1 immediately after the master node is initialised, thus stabilising the whole system faster

also, metrics got a bit better (-5sec; both pr's out and released minikube-rls are based on the latest v1.18.0-beta.0):

out/minikube start  2.48s user 1.39s system 6% cpu 55.720 total
minikube-rls start  2.38s user 1.67s system 6% cpu 59.158 total

out/minikube start --vm-driver=docker --nodes=3  4.84s user 2.54s system 8% cpu 1:27.61 total
minikube-rls start --vm-driver=docker --nodes=3  4.40s user 2.70s system 7% cpu 1:32.79 total

out/minikube start --vm-driver=docker --nodes=3 --wait=all  6.52s user 2.68s system 4% cpu 3:31.89 total
minikube-rls start --vm-driver=docker --nodes=3 --wait=all  6.59s user 2.99s system 4% cpu 3:37.16 total

[minikube-bot]

Can one of the admins verify this patch?

[medyagh]

/ok-to-test

[medyagh]

/ok-to-test

[minikube-pr-bot]

kvm2 Driver
Times for minikube: 67.9s 69.9s 69.3s
Average time for minikube: 69.0s

Times for Minikube (PR 10656): 72.0s 68.3s 71.9s
Average time for Minikube (PR 10656): 70.7s

Averages Time Per Log

+--------------------------------------------+----------+---------------------+
|                    LOG                     | MINIKUBE | MINIKUBE (PR 10656) |
+--------------------------------------------+----------+---------------------+
| * minikube v1.18.0 on Debian               | 0.0s     | 0.0s                |
| 9.11 (kvm/amd64)                           |          |                     |
| * Using the kvm2 driver based              | 0.0s     | 0.0s                |
| on user configuration                      |          |                     |
| * Starting control plane node              | 0.0s     | 0.0s                |
| minikube in cluster minikube               |          |                     |
| * Creating kvm2 VM (CPUs=2,                | 41.3s    | 43.4s               |
| Memory=3700MB, Disk=20000MB)               |          |                     |
| ...                                        |          |                     |
| * Preparing Kubernetes v1.20.2             | 9.8s     | 2.1s                |
| on Docker 20.10.3 ...                      |          |                     |
|   - Generating certificates                | 3.0s     | 4.4s                |
| and keys ...                               |          |                     |
|   - Booting up control plane               | 11.3s    | 16.3s               |
| ...                                        |          |                     |
|   - Configuring RBAC rules ...             | 1.1s     | 1.7s                |
| * Verifying Kubernetes                     | 0.1s     | 0.1s                |
| components...                              |          |                     |
|   - Using image                            | 1.8s     | 1.5s                |
| gcr.io/k8s-minikube/storage-provisioner:v4 |          |                     |
| * Enabled addons:                          | 0.6s     |                     |
| default-storageclass,                      |          |                     |
| storage-provisioner                        |          |                     |
| * Done! kubectl is now                     | 0.0s     | 0.0s                |
| configured to use "minikube"               |          |                     |
| cluster and "default"                      |          |                     |
| namespace by default                       |          |                     |
+--------------------------------------------+----------+---------------------+

docker Driver
Times for minikube: 27.9s 26.6s 27.0s
Average time for minikube: 27.1s

Times for Minikube (PR 10656): 28.2s 26.7s 28.1s
Average time for Minikube (PR 10656): 27.7s

Averages Time Per Log

+--------------------------------------------+----------+---------------------+
|                    LOG                     | MINIKUBE | MINIKUBE (PR 10656) |
+--------------------------------------------+----------+---------------------+
| * minikube v1.18.0 on Debian               | 0.2s     | 0.2s                |
| 9.11 (kvm/amd64)                           |          |                     |
| * Using the docker driver                  | 0.1s     | 0.1s                |
| based on user configuration                |          |                     |
| * Starting control plane node              | 0.1s     | 0.1s                |
| minikube in cluster minikube               |          |                     |
| * Creating docker container                | 10.0s    | 10.1s               |
| (CPUs=2, Memory=3700MB) ...                |          |                     |
| * Preparing Kubernetes v1.20.2             | 15.2s    | 16.0s               |
| on Docker 20.10.3 ...                      |          |                     |
| * Verifying Kubernetes                     | 0.1s     | 0.1s                |
| components...                              |          |                     |
|   - Using image                            | 1.3s     | 1.1s                |
| gcr.io/k8s-minikube/storage-provisioner:v4 |          |                     |
| * Enabled addons:                          | 0.1s     | 0.1s                |
| storage-provisioner,                       |          |                     |
| default-storageclass                       |          |                     |
| * Done! kubectl is now                     | 0.0s     | 0.0s                |
| configured to use "minikube"               |          |                     |
| cluster and "default"                      |          |                     |
| namespace by default                       |          |                     |
+--------------------------------------------+----------+---------------------+

[medyagh]

thank you

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: medyagh, prezha

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