Templating¶

Chainsaw simplifies dynamic configuration with native templating support.

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.

Templating in Chainsaw solves exactly this kind of problem.

Syntax¶

Tip

Resource templating is heavily based on bindings and uses JMESPath language.

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)

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