Merge pull request #60174 from hyperbolic2346/mwilson/metrics-server

Automatic merge from submit-queue. If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Adding metrics server

**What this PR does / why we need it**:
Adds support for the metrics server in the kubernetes-master charm. This allows the use of a horizontal pod autoscaler.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #
https://github.com/juju-solutions/bundle-canonical-kubernetes/issues/484
**Special notes for your reviewer**:
Needs to go in after https://github.com/juju-solutions/cdk-addons/pull/28
**Release note**:

```release-note
kubernetes-master charm now supports metrics server for horizontal pod autoscaler.
```

cluster/juju/layers/kubernetes-master/config.yaml

@@ -86,3 +86,8 @@ options:
     description: |
       The storage backend for kube-apiserver persistence. Can be "etcd2", "etcd3", or
       "auto". Auto mode will select etcd3 on new installations, or etcd2 on upgrades.
+  enable-metrics:
+    type: boolean
+    default: true
+    description: |
+      If true the metrics server for Kubernetes will be deployed onto the cluster.

cluster/juju/layers/kubernetes-master/reactive/kubernetes_master.py

@@ -640,12 +640,14 @@ def configure_cdk_addons():
     remove_state('cdk-addons.configured')
     dbEnabled = str(hookenv.config('enable-dashboard-addons')).lower()
     dnsEnabled = str(hookenv.config('enable-kube-dns')).lower()
+    metricsEnabled = str(hookenv.config('enable-metrics')).lower()
     args = [
         'arch=' + arch(),
         'dns-ip=' + get_deprecated_dns_ip(),
         'dns-domain=' + hookenv.config('dns_domain'),
         'enable-dashboard=' + dbEnabled,
-        'enable-kube-dns=' + dnsEnabled
+        'enable-kube-dns=' + dnsEnabled,
+        'enable-metrics=' + metricsEnabled
     ]
     check_call(['snap', 'set', 'cdk-addons'] + args)
     if not addons_ready():
@@ -1183,6 +1185,18 @@ def configure_apiserver(etcd_connection_string, leader_etcd_version):
     else:
         api_opts['admission-control'] = ','.join(admission_control)
 
+    if get_version('kube-apiserver') > (1, 6) and \
+       hookenv.config('enable-metrics'):
+        api_opts['requestheader-client-ca-file'] = ca_cert_path
+        api_opts['requestheader-allowed-names'] = 'client'
+        api_opts['requestheader-extra-headers-prefix'] = 'X-Remote-Extra-'
+        api_opts['requestheader-group-headers'] = 'X-Remote-Group'
+        api_opts['requestheader-username-headers'] = 'X-Remote-User'
+        api_opts['proxy-client-cert-file'] = client_cert_path
+        api_opts['proxy-client-key-file'] = client_key_path
+        api_opts['enable-aggregator-routing'] = 'true'
+        api_opts['client-ca-file'] = ca_cert_path
+
     configure_kubernetes_service('kube-apiserver', api_opts, 'api-extra-args')
     restart_apiserver()