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

Template String	Description	Example
PREVIEWHQ_HOSTNAME	The hostname of the deployment, which will point to the root	my-pr-branch.nrmitchi.envs.dev
PREVIEWHQ_CLUSTER_HOSTNAME	The hostname of the cluster which the deployment is deployed on	nrmitchi.envs.dev
PREVIEWHQ_NAMESPACE	The namespace which the deployment is deployed in to	my-pr-branch
PREVIEWHQ_REVISION	The git hash being deployed
PREVIEWHQ_IMAGE_REPOSITORY	The URL of the Preview-provided Docker image repository that

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