Template Strings

Template Strings are strings which are dynamically replaced by Preview during a deploy, allowing you to inject environment-specific values into your deployment.

Preview supports the use of Template Strings in both for all chart values and Kubernetes manifest files under the ./preview directory.

For example, it is recommended to use the PREVIEWHQ_HOSTNAME as part of your application's Ingress specification:

# .preview/chart-values/
ingress:
  enabled: true
  annotations:
    kubernetes.io/tls-acme: "true"
  path: /
  hosts:
    - host: ${PREVIEWHQ_HOSTNAME}
      paths:
        - /
  tls:
   - secretName: tls-secret
     hosts:
       - ${PREVIEWHQ_CLUSTER_HOSTNAME}
       - ${PREVIEWHQ_HOSTNAME}

There are 2 sets of Template Strings which can be utilized: one static set across all builds, and one set that is dynamically build based on image builds.

Static Template Strings

Dynamic Template Strings

For each addition image specified in the images block of the configuration, Preview injects a PREVIEWHQ_CUSTOM_IMAGE_TAG_{} string, which is the Docker tag which was used for that custom build within the Docker image registry.

For example, if images is as follows:

images:
  - name: frontend
    dockerfile: ./src/react/Dockerfile
    context: ./src/react
  - name: backend
    dockerfile: ./src/flask/Dockerfile
    context: ./src/flask

The the following additional Templates Strings are available:

• PREVIEWHQ_CUSTOM_IMAGE_TAG_FRONTEND

• PREVIEWHQ_CUSTOM_IMAGE_TAG_BACKEND