Gateway Artifact Templating

Gateway artifact files (YAML/JSON) support Go text/template expressions for injecting dynamic values at startup. Templates are rendered on the raw artifact string before YAML/JSON parsing, so expressions work in any string field across the entire artifact — upstream, auth, policy params, metadata, etc.

Available functions

env

Reads a value from an environment variable.

{{ env "KEY" }}

Returns an empty string if the variable is not set. Use | default to provide a fallback:

{{ env "BACKEND_URL" | default "http://localhost:8080" }}

required

Like env, but fails at startup if the variable is not set or empty. Use this to enforce that a value must be provided:

{{ required "BACKEND_URL" }}

If the variable is missing, the gateway will not start and will log which variable is required.

redact

Marks a resolved value for redaction in config dumps. Any field rendered with | redact will appear as ***REDACTED*** in the gateway's config dump output instead of its actual value.

{{ env "API_KEY" | redact }}

Use | redact for any sensitive value injected from an environment variable (API keys, tokens, passwords).

default

Provides a fallback value when the input is empty:

{{ env "LOG_LEVEL" | default "info" }}

Can be combined with any other function in a pipeline.

Combining functions

Functions compose as pipelines:

{{ env "KEY" | default "fallback" }}
{{ env "KEY" | redact }}
{{ required "KEY" | redact }}

Example

apiVersion: gateway.api-platform.wso2.com/v1alpha1
kind: RestApi
metadata:
  name: orders-api-v1
spec:
  context: /orders/v1
  upstream:
    main:
      url: '{{ env "ORDERS_BACKEND_URL" | default "http://orders-svc:8080" }}'
    auth:
      apiKey: '{{ required "ORDERS_API_KEY" | redact }}'
  policies:
    - name: set-headers
      version: v1
      params:
        request:
          headers:
            - name: X-Env
              value: '{{ env "DEPLOYMENT_ENV" | default "production" }}'

In this example:

• ORDERS_BACKEND_URL is optional — falls back to the default URL if not set.
• ORDERS_API_KEY is required — the gateway will not start if it is missing, and the value is redacted in config dumps.
• DEPLOYMENT_ENV is optional with a default of production.