Helm chart: Add enableServiceLinks (#7129)

**What this PR does / why we need it**:
This is to allow disable `enableServiceLinks` so that the service
environments are not injected into the pods where in my scenario Loki is
deployed in the same namespace as the Knative services resulted the Loki
pod unable to start up due to too many service environment being
injected.

Reference issue for pod unable to startup due to too many services:
https://github.com/kubernetes/kubernetes/issues/84539#issue-514261281

Co-authored-by: Trevor Whitney <trevorjwhitney@gmail.com>

docs/sources/installation/helm/reference.md

@@ -1583,6 +1583,15 @@ See values.yaml
   "readOnlyRootFilesystem": true
 }
 </pre>
+</td>
+		</tr>
+		<tr>
+			<td>loki.enableServiceLinks</td>
+			<td>bool</td>
+			<td>Should enableServiceLinks be enabled. Default to enable</td>
+			<td><pre lang="json">
+true
+</pre>
 </td>
 		</tr>
 		<tr>

production/helm/loki/Chart.yaml

@@ -4,7 +4,7 @@ name: loki
 description: Helm chart for Grafana Loki in simple, scalable mode
 type: application
 appVersion: 2.7.0
-version: 4.1.0
+version: 4.2.0
 home: https://grafana.github.io/helm-charts
 sources:
   - https://github.com/grafana/loki

production/helm/loki/README.md

@@ -1,6 +1,6 @@
 # loki
 
-![Version: 4.1.0](https://img.shields.io/badge/Version-4.1.0-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.7.0](https://img.shields.io/badge/AppVersion-2.7.0-informational?style=flat-square)
+![Version: 4.2.0](https://img.shields.io/badge/Version-4.2.0-informational?style=flat-square) ![Type: application](https://img.shields.io/badge/Type-application-informational?style=flat-square) ![AppVersion: 2.7.0](https://img.shields.io/badge/AppVersion-2.7.0-informational?style=flat-square)
 
 Helm chart for Grafana Loki in simple, scalable mode
 

production/helm/loki/templates/_helpers.tpl

@@ -651,3 +651,14 @@ http {
   }
 }
 {{- end }}
+
+{{/* Configure enableServiceLinks in pod */}}
+{{- define "loki.enableServiceLinks" -}}
+{{- if semverCompare ">=1.13-0" .Capabilities.KubeVersion.Version -}}
+{{- if or (.Values.loki.enableServiceLinks) (ne .Values.loki.enableServiceLinks false) -}}
+enableServiceLinks: true
+{{- else -}}
+enableServiceLinks: false
+{{- end -}}
+{{- end -}}
+{{- end -}}

production/helm/loki/templates/gateway/deployment-gateway.yaml

@@ -37,7 +37,8 @@ spec:
         {{- end }}
         {{- include "loki.gatewaySelectorLabels" . | nindent 8 }}
     spec:
-      serviceAccountName: {{ include "loki.serviceAccountName" . -}}
+      serviceAccountName: {{ include "loki.serviceAccountName" . }}
+      {{ include "loki.enableServiceLinks" . }}
       {{- with .Values.imagePullSecrets }}
       imagePullSecrets:
         {{- toYaml . | nindent 8 }}

production/helm/loki/templates/read/statefulset-read.yaml

@@ -53,6 +53,7 @@ spec:
     spec:
       serviceAccountName: {{ include "loki.serviceAccountName" . }}
       automountServiceAccountToken: {{ .Values.serviceAccount.automountServiceAccountToken }}
+      {{ include "loki.enableServiceLinks" . }}
       {{- with .Values.imagePullSecrets }}
       imagePullSecrets:
         {{- toYaml . | nindent 8 }}

production/helm/loki/templates/single-binary/statefulset.yaml

@@ -44,6 +44,7 @@ spec:
     spec:
       serviceAccountName: {{ include "loki.serviceAccountName" . }}
       automountServiceAccountToken: {{ .Values.serviceAccount.automountServiceAccountToken }}
+      {{ include "loki.enableServiceLinks" . }}
       {{- with .Values.imagePullSecrets }}
       imagePullSecrets:
         {{- toYaml . | nindent 8 }}

production/helm/loki/templates/write/statefulset-write.yaml

@@ -45,6 +45,7 @@ spec:
     spec:
       serviceAccountName: {{ include "loki.serviceAccountName" . }}
       automountServiceAccountToken: {{ .Values.serviceAccount.automountServiceAccountToken }}
+      {{ include "loki.enableServiceLinks" . }}
       {{- with .Values.imagePullSecrets }}
       imagePullSecrets:
         {{- toYaml . | nindent 8 }}

production/helm/loki/values.yaml

@@ -69,6 +69,8 @@ loki:
       drop:
         - ALL
     allowPrivilegeEscalation: false
+  # -- Should enableServiceLinks be enabled. Default to enable
+  enableServiceLinks: true
   # -- Specify an existing secret containing loki configuration. If non-empty, overrides `loki.config`
   existingSecretForConfig: ""
   # -- Config file contents for Loki
@@ -1141,7 +1143,6 @@ gateway:
     htpasswd: >-
       {{ htpasswd (required "'gateway.basicAuth.username' is required" .Values.gateway.basicAuth.username) (required "'gateway.basicAuth.password' is required" .Values.gateway.basicAuth.password) }}
 
-
     # -- Existing basic auth secret to use. Must contain '.htpasswd'
     existingSecret: null
   # Configures the readiness probe for the gateway