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