Helm yaml command output for the default value of JAVA_OPTS_APPEND in bitnami/Keycloak - yaml

Question

Could anybody please help me understand this command - What would be the output of this key -value pair:
JAVA_OPTS_APPEND: {{ printf "-Djgroups.dns.query=%s-headless.%s.svc.%s" (include "common.names.fullname" .) (include "common.names.namespace" .) .Values.clusterDomain | quote }}
where
common.names.fullname: ""
common.names.namespace: ""
clusterDomain: cluster.local
This piece of code is from here:
https://github.com/bitnami/charts/blob/main/bitnami/keycloak/templates/configmap-env-vars.yaml
I am fairly new to Kubernetes and I am trying to understand what would be the value of JAVA_OPTS_APPEND.
Thanks in advance.
Nafee

Answer 1

You can render helm templates locally with helm template command, this will render your values so you see the outputs of this command.
If you don't enough permissions on your Kubernetes cluster, you can spin a local mininkube or kind instance and then render the template:
helm repo add bitnami https://charts.bitnami.com/bitnami
helm template bitnami/keycloak --namespace mhajeb
In the rendered manifest you will find the following ConfigMap:
# Source: keycloak/templates/configmap-env-vars.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: release-name-keycloak-env-vars
namespace: "mhajeb"
labels:
app.kubernetes.io/name: keycloak
helm.sh/chart: keycloak-13.0.4
app.kubernetes.io/instance: release-name
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/component: keycloak
data:
KEYCLOAK_ADMIN: "user"
KEYCLOAK_HTTP_PORT: "8080"
KEYCLOAK_PROXY: "passthrough"
KEYCLOAK_ENABLE_STATISTICS: "false"
KEYCLOAK_DATABASE_HOST: "release-name-postgresql"
KEYCLOAK_DATABASE_PORT: "5432"
KEYCLOAK_DATABASE_NAME: "bitnami_keycloak"
KEYCLOAK_DATABASE_USER: "bn_keycloak"
KEYCLOAK_PRODUCTION: "false"
KEYCLOAK_ENABLE_HTTPS: "false"
KEYCLOAK_CACHE_TYPE: "ispn"
KEYCLOAK_CACHE_STACK: "kubernetes"
JAVA_OPTS_APPEND: "-Djgroups.dns.query=release-name-keycloak-headless.mhajeb.svc.cluster.local"
KEYCLOAK_LOG_OUTPUT: "default"
KC_LOG_LEVEL: "INFO"
Now note that JAVA_OPTS_APPEND: {{ printf "-Djgroups.dns.query=%s-headless.%s.svc.%s" (include "common.names.fullname" .) (include "common.names.namespace" .) .Values.clusterDomain | quote }} rendered:
JAVA_OPTS_APPEND: "-Djgroups.dns.query=release-name-keycloak-headless.mhajeb.svc.cluster.local"
And that was done with printf function which rendered common.names.fullname and common.names.namespacce from the templates helpers which are defined in the "parent" chart:
{{/*
Create a default fully qualified app name.
We truncate at 63 chars because some Kubernetes name fields are limited to this (by the DNS naming spec).
If release name contains chart name it will be used as a full name.
*/}}
{{- define "common.names.fullname" -}}
{{- if .Values.fullnameOverride -}}
{{- .Values.fullnameOverride | trunc 63 | trimSuffix "-" -}}
{{- else -}}
{{- $name := default .Chart.Name .Values.nameOverride -}}
{{- if contains $name .Release.Name -}}
{{- .Release.Name | trunc 63 | trimSuffix "-" -}}
{{- else -}}
{{- printf "%s-%s" .Release.Name $name | trunc 63 | trimSuffix "-" -}}
{{- end -}}
{{- end -}}
{{- end -}}
and
{{/*
Allow the release namespace to be overridden for multi-namespace deployments in combined charts.
*/}}
{{- define "common.names.namespace" -}}
{{- default .Release.Namespace .Values.namespaceOverride | trunc 63 | trimSuffix "-" -}}
{{- end -}}
TLDR;
It is taking the Chart, Release names as defaults. And if you want to override them have a look at the documentation: https://github.com/bitnami/charts/tree/main/bitnami/keycloak#common-parameters, or the templates :), and just set:
fullnameOverride String to fully override common.names.fullname
namespaceOverride String to fully override common.names.namespace
Other examples
helm template my-food-release bitnami/keycloak --namespace mhajeb
Result:
# Source: keycloak/templates/configmap-env-vars.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: my-food-release-keycloak-env-vars
namespace: "mhajeb"
labels:
app.kubernetes.io/name: keycloak
helm.sh/chart: keycloak-13.0.4
app.kubernetes.io/instance: my-food-release
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/component: keycloak
data:
KEYCLOAK_DATABASE_HOST: "my-food-release-postgresql"
...
JAVA_OPTS_APPEND: "-Djgroups.dns.query=my-food-release-keycloak-headless.mhajeb.svc.cluster.local"
...
helm template my-food-release bitnami/keycloak --namespace mhajeb --set fullnameOverride=daNewName --set namespaceOverride=daNewNamespaceOverride
Result:
# Source: keycloak/templates/configmap-env-vars.yaml
apiVersion: v1
kind: ConfigMap
metadata:
name: daNewName-env-vars
namespace: "daNewNamespaceOverride"
labels:
app.kubernetes.io/name: keycloak
helm.sh/chart: keycloak-13.0.4
app.kubernetes.io/instance: my-food-release
app.kubernetes.io/managed-by: Helm
app.kubernetes.io/component: keycloak
data:
...
JAVA_OPTS_APPEND: "-Djgroups.dns.query=daNewName-headless.daNewNamespaceOverride.svc.cluster.local"
...