Use resource templating¶

Chainsaw simplifies dynamic resource configuration with native resource templating support.

Sometimes things we need to create resources or assertions are only known at runtime.

In the past, users have created all sorts of hacks using tools like envsubst for dynamic substitution of env-variables. Those workarounds usually lack flexibility and introduce new problems like hiding the real resources from Chainsaw, preventing it from cleaning resources properly.

Leverage bindings¶

In the template below, we are using the $namespace binding at two different places, effectively injecting the ephemeral namespace name in the name and the data.foo fields:

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  steps:
  - assert:
      resource:
        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: ($namespace)
        data:
          foo: ($namespace)

Leverage JMESPath¶

In the template below, we are using the JMESPath join function to create a unique resource name:

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  steps:
  - apply:
      resource:
        apiVersion: v1
        kind: ConfigMap
        metadata:
          name: (join('-', [$namespace, 'cm']))
        data:
          foo: bar

Next step¶

Combining bindings and templates with operation outputs allows even more flexibility to pass arbitrary data from one operation to another.