What does & and * denote in a helm template?
apiVersion: apps/v1
kind: Deployment
metadata:
name: {{ template "seleniumGrid.chromeNode.fullname" . }}
namespace: {{ .Release.Namespace }}
labels: &chrome_node_labels //**& here**
app: selenium-chrome-node
app.kubernetes.io/name: selenium-chrome-node
{{- include "seleniumGrid.commonLabels" . | nindent 4 }}
{{- with .Values.chromeNode.labels }}
{{- toYaml . | nindent 4 }}
{{- end }}
{{- with .Values.customLabels }}
{{- toYaml . | nindent 4 }}
{{- end }}
spec:
replicas: {{ .Values.chromeNode.replicas }}
selector:
matchLabels:
app: selenium-chrome-node
app.kubernetes.io/instance: {{ .Release.Name }}
template:
metadata:
labels: *chrome_node_labels // **star here **
annotations:
This looks like the usage of YAML anchors, but I remember it would result in an error if used directly in the Helm templates. I guess they might be doing a second rendering here, where the YAML is parsed first.
Anchors and aliases. There are 2 parts to this:
The anchor & which defines a chunk of configuration
The alias * used to refer to that chunk elsewhere
So in the example below we use &build-test to define a step entity, which has several lines for reuse, and the alias *build-test to reuse it.
definitions:
steps:
- step: &build-test
name: Build and test
script:
- mvn package
artifacts:
- target/**
pipelines:
branches:
develop:
- step: *build-test
main:
- step: *build-test