[helm] Refactor validation warning and error checks

Author: morazow

helm/README.md

@@ -28,14 +28,37 @@ For how to build your local Fluss image and use it in Minikube refer to the
 Refer to the [official documentation](https://fluss.apache.org/docs/next/install-deploy/deploying-with-helm/#configuration-parameters)
 as well for configuration values.
 
-We use the [`helm-unittest`](https://github.com/helm-unittest/helm-unittest) plugin for testing Fluss Helm charts.  
+We use the [`helm-unittest`](https://github.com/helm-unittest/helm-unittest) plugin for testing Fluss Helm charts.
 You can run tests locally via:
 
 ```bash
 # From the /helm folder:
 docker run -ti --rm -v $(pwd):/apps helmunittest/helm-unittest .
 ```
 
+### Validation Checks
+
+The chart runs the validation checks at install or upgrade time using templates in `_validate.tpl` file.
+
+The warnings are printed to the user, but errors abort the deployment.
+
+To add new validations, for example for a new feature:
+
+1. Define `fluss.<feature>.validateWarning` or `fluss.<feature>.validateError` templates in the feature `_<feature>.tpl` template file.
+2. Add the corresponding `include` calls to `fluss.validateWarning` or `fluss.validateError` in `_validate.tpl` template file.
+
+For example, for the `security` checks, include and update these methods in the `_validate.tpl` file:
+
+```
+{{- define "fluss.validateWarning" -}}
+{{- include "fluss.security.validateWarning" . -}}
+{{- end -}}
+
+{{- define "fluss.validateError" -}}
+{{- include "fluss.security.validateError" . -}}
+{{- end -}}
+```
+
 ## Contributing
 
 Follow the [development section](#development) for local development.

helm/templates/NOTES.txt

@@ -20,4 +20,4 @@ CHART NAME: {{ .Chart.Name }}
 CHART VERSION: {{ .Chart.Version }}
 APP VERSION: {{ .Chart.AppVersion }}
 
-{{ include "fluss.security.validateValues" . }}
+{{ include "fluss.validate" . }}

helm/templates/_security.tpl

@@ -170,33 +170,25 @@ Usage:
 {{- end -}}
 
 {{/*
-Compile all warnings and errors into a single message.
+Collects security warning messages.
 Usage:
-  include "fluss.security.validateValues" .
+  include "fluss.security.validateWarning" .
 */}}
-{{- define "fluss.security.validateValues" -}}
+{{- define "fluss.security.validateWarning" -}}
+{{- include "fluss.security.sasl.warnInternalUser" . -}}
+{{- end -}}
 
+{{/*
+Collects security error messages.
+Usage:
+  include "fluss.security.validateError" .
+*/}}
+{{- define "fluss.security.validateError" -}}
 {{- $errMessages := list -}}
 {{- $errMessages = append $errMessages (include "fluss.security.sasl.validateMechanisms" .) -}}
 {{- $errMessages = append $errMessages (include "fluss.security.sasl.validateClientPlainUsers" .) -}}
-
 {{- $errMessages = without $errMessages "" -}}
-{{- $errMessage := join "\n" $errMessages -}}
-
-{{- $warnMessages := list -}}
-{{- $warnMessages = append $warnMessages (include "fluss.security.sasl.warnInternalUser" .) -}}
-
-{{- $warnMessages = without $warnMessages "" -}}
-{{- $warnMessage := join "\n" $warnMessages -}}
-
-{{- if $warnMessage -}}
-{{-   printf "\nVALUES WARNING:\n%s" $warnMessage -}}
-{{- end -}}
-
-{{- if $errMessage -}}
-{{-   printf "\nVALUES VALIDATION:\n%s" $errMessage | fail -}}
-{{- end -}}
-
+{{- join "\n" $errMessages -}}
 {{- end -}}
 
 {{/*

helm/templates/_validate.tpl

@@ -0,0 +1,65 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+{{/*
+Collects all warning messages from validation methods.
+Usage:
+  include "fluss.validateWarning" .
+*/}}
+{{- define "fluss.validateWarning" -}}
+{{- include "fluss.security.validateWarning" . -}}
+{{- end -}}
+
+{{/*
+Collects all error messages from validation methods.
+Usage:
+  include "fluss.validateError" .
+*/}}
+{{- define "fluss.validateError" -}}
+{{- include "fluss.security.validateError" . -}}
+{{- end -}}
+
+{{/*
+Global validation checks entry point.
+Collects all warnings and errors, prints warnings and fails on errors.
+Usage:
+  include "fluss.validate" .
+*/}}
+{{- define "fluss.validate" -}}
+
+{{- $warnMessages := list -}}
+{{- $warnMessages = append $warnMessages (include "fluss.validateWarning" .) -}}
+
+{{- $warnMessages = without $warnMessages "" -}}
+{{- $warnMessage := join "\n" $warnMessages -}}
+
+{{- $errMessages := list -}}
+{{- $errMessages = append $errMessages (include "fluss.validateError" .) -}}
+
+{{- $errMessages = without $errMessages "" -}}
+{{- $errMessage := join "\n" $errMessages -}}
+
+{{- if $warnMessage -}}
+{{-   printf "\nVALUES WARNING:\n%s" $warnMessage -}}
+{{- end -}}
+
+{{- if $errMessage -}}
+{{-   printf "\nVALUES VALIDATION:\n%s" $errMessage | fail -}}
+{{- end -}}
+
+{{- end -}}