chart: add defaultNodeSelector for all components

Until now all the components that were not a daemonset and needed to be
deployed on a node contained a config option to indicate a node selector
for the allocation. This commits adds a new global option that allows to
set a node selector that will be applied to all the components that do
not declare one. If any component declares a node selector this last one
will have always more priority.

JIRA Refs:
- MONIT-4003

README.md

@@ -37,6 +37,7 @@ At `docs/installation_guide.md` you will find the initial setup and installation
 | logs.fluentbit.scrapeInterval | string | `"15s"` | interval used by the local prometheus (if installed) to scrape metrics from logs fluentbits |
 | logs.fluentbit.service | string | Daemon mode off listening on port 2020. See `values.yaml`. | fluentbit service configuration options in a multiline string |
 | metrics.enabled | bool | `true` | indicates if all metrics components should be enabled or not. If set to false no metrics component will be installed nor configured |
+| metrics.defaultNodeSelector | map | `{}` | if set will be used as `nodeSelector` for those components that allow one |
 | metrics.fluentbit.enable | bool | `true` | if true fluentbit daemon set will be installed |
 | metrics.fluentbit.diskMaxCache | string | `5G` | max size for in-disk storage for fluent-bit |
 | metrics.fluentbit.nodeSelector | hash | `"nil"` | fluentbit statefulset node selectors |

templates/fluentbit-metrics/statefulset.yaml

@@ -38,10 +38,10 @@ spec:
           {{- if .Values.metrics.fluentbit.extraVolumeMounts }}
             {{- toYaml .Values.metrics.fluentbit.extraVolumeMounts | nindent 6 }}
           {{- end }}
-      {{- with .Values.metrics.fluentbit.nodeSelector }}
+      {{- if or (.Values.metrics.defaultNodeSelector) (.Values.metrics.fluentbit.nodeSelector) }}
       nodeSelector:
-        {{- toYaml . | nindent 8 }}
-      {{- end }}      
+        {{- .Values.metrics.fluentbit.nodeSelector | default .Values.metrics.defaultNodeSelector | toYaml | nindent 8 }}
+      {{- end }}
       volumes:
         - name: config
           configMap: 

templates/kube_state/deployment.yaml

@@ -49,8 +49,6 @@ spec:
             type: RuntimeDefault
       nodeSelector:
         kubernetes.io/os: linux
-      {{- with .Values.metrics.kubeState.nodeSelector }}
-        {{- toYaml . | nindent 8 }}
-      {{- end }} 
+      {{- .Values.metrics.kubeState.nodeSelector | default .Values.metrics.defaultNodeSelector | toYaml | nindent 8 }}
       serviceAccountName: it-monit-metrics-collector-kubestate
 {{- end -}}

templates/prometheus/prometheus.yaml

@@ -11,10 +11,8 @@ spec:
   retention: {{ .Values.metrics.prometheus.server.retention }}
   externalLabels:
     k8s_cluster_name: {{ .Values.kubernetes.clusterName }}
-  {{- with .Values.metrics.prometheus.server.nodeSelector }}
   nodeSelector:
-    {{- toYaml . | nindent 6 }}
-  {{- end }} 
+    {{- .Values.metrics.prometheus.server.nodeSelector | default .Values.metrics.defaultNodeSelector | toYaml | nindent 4 }}
   serviceAccountName: it-monit-metrics-collector-prometheus
   resources:
     requests:

templates/prometheus_operator/deployment.yaml

@@ -44,9 +44,7 @@ spec:
           readOnlyRootFilesystem: true
       nodeSelector:
         kubernetes.io/os: linux
-      {{- with .Values.metrics.prometheus.operator.nodeSelector }}
-        {{- toYaml . | nindent 8 }}
-      {{- end }} 
+        {{- .Values.metrics.prometheus.operator.nodeSelector | default .Values.metrics.defaultNodeSelector | toYaml | nindent 8 }}
       securityContext:
         runAsNonRoot: true
         runAsUser: 65534

values.yaml

@@ -24,6 +24,9 @@ metrics:
   # -- indicates if all metrics components should be enabled or not. If set to false no metrics component will be installed nor configured
   enabled: true
 
+  # -- the default node selector will be applied when possible. In to the following components: metrics collectors (prometheus and fluentbit), metrics exporters (kube state).
+  defaultNodeSelector: {}
+
   # Node exporter is used to scrape node resources metrics like cpu, memory
   # or network.
   nodeExporter:
@@ -42,6 +45,7 @@ metrics:
   # Kube state is used to scrape metrics from kubernetes api, like limits
   # and resources.
   kubeState:
+  # If set it will override the metrics.defaultNodeSelector.
     nodeSelector: {}
     # -- if true kube state will be installed together with a service monitor
     enabled: true
@@ -62,6 +66,7 @@ metrics:
     enabled: true
     # -- specific configuration for the prometheus operator
     operator:
+      # If set it will override the metrics.defaultNodeSelector.
       nodeSelector: {}
       resources:
         requests:
@@ -71,6 +76,7 @@ metrics:
           cpu: "100m"
           memory: "100Mi"
     server:
+      # If set it will override the metrics.defaultNodeSelector.
       nodeSelector: {}
       # -- prometheus version to use by the local cluster prometheus
       version: "v2.50.0"
@@ -118,6 +124,7 @@ metrics:
   fluentbit:
     # -- if true fluentbit metrics forwarder will be installed
     enabled: true
+    # If set it will override the metrics.defaultNodeSelector.
     nodeSelector: {}
     resources:
       requests: