[stable/datadog] Add validity checks on clusterName (#19327)

The cluster name parameter has been introduced to disambiguate nodes
having the same name in different clusters.

Cluster names are, for ex., used to build hostnames and must therefore
comply with some rules.

We enforce here the same rules as the ones enforced by GKE:
https://cloud.google.com/kubernetes-engine/docs/reference/rest/v1beta1/projects.locations.clusters#Cluster.FIELDS.name

The DataDog agent itself is already checking the validity of cluster names since
DataDog/datadog-agent#4492.

The goal of this change in the helm chart is to catch issues as early as possible because
having a clear error message from helm is smarter than having to dig in the logs of
a failing agent.

Signed-off-by: Lénaïc Huard <lenaic.huard@datadoghq.com>

stable/datadog/Chart.yaml

@@ -1,6 +1,6 @@
 apiVersion: v1
 name: datadog
-version: 1.38.11
+version: 1.38.12
 appVersion: "6"
 description: DataDog Agent
 keywords:

stable/datadog/templates/cluster-agent-deployment.yaml

@@ -101,6 +101,9 @@ spec:
             value: "kube_services"
           {{- end }}
           {{- if .Values.datadog.clusterName }}
+          {{- if not (regexMatch "^[a-z]([a-z0-9\\-]{0,38}[a-z0-9])?$" .Values.datadog.clusterName) }}
+          {{- fail "Your `clusterName` isn’t valid. It must start with a lowercase letter followed by up to 39 lowercase letters, numbers, or hyphens and cannot end with a hyphen."}}
+          {{- end}}
           - name: DD_CLUSTER_NAME
             value: {{ .Values.datadog.clusterName | quote }}
           {{- end }}

stable/datadog/templates/container-agent.yaml

@@ -15,6 +15,9 @@
   env:
     {{- include "containers-common-env" . | nindent 4 }}
     {{- if .Values.datadog.clusterName }}
+    {{- if not (regexMatch "^[a-z]([a-z0-9\\-]{0,38}[a-z0-9])?$" .Values.datadog.clusterName) }}
+    {{- fail "Your `clusterName` isn’t valid. It must start with a lowercase letter followed by up to 39 lowercase letters, numbers, or hyphens and cannot end with a hyphen."}}
+    {{- end}}
     - name: DD_CLUSTER_NAME
       value: {{ .Values.datadog.clusterName | quote }}
     {{- end }}

stable/datadog/templates/container-agents.yaml

@@ -26,6 +26,9 @@
           name: {{ template "datadog.apiSecretName" . }}
           key: api-key
     {{- if .Values.datadog.clusterName }}
+    {{- if not (regexMatch "^[a-z]([a-z0-9\\-]{0,38}[a-z0-9])?$" .Values.datadog.clusterName) }}
+    {{- fail "Your `clusterName` isn’t valid. It must start with a lowercase letter followed by up to 39 lowercase letters, numbers, or hyphens and cannot end with a hyphen."}}
+    {{- end}}
     - name: DD_CLUSTER_NAME
       value: {{ .Values.datadog.clusterName | quote }}
     {{- end }}

stable/datadog/values.yaml

@@ -71,6 +71,12 @@ datadog:
 
   ## @param clusterName - string - optional
   ## Set a unique cluster name to allow scoping hosts and Cluster Checks easily
+  ## The name must be unique and can be up to 40 characters with the following restrictions:
+  ## * Lowercase letters, numbers, and hyphens only.
+  ## * Must start with a letter.
+  ## * Must end with a number or a letter.
+  ## These are the same rules as the one enforced by GKE on the same cluster name parameter:
+  ## https://cloud.google.com/kubernetes-engine/docs/reference/rest/v1beta1/projects.locations.clusters#Cluster.FIELDS.name
   #
   # clusterName: <CLUSTER_NAME>