Use operation outputs¶

Operation outputs can be useful for communicating and reusing computation results across operations.

Lifetime of outputs¶

Once an output has been added to the bindings context, this binding will be available to all following operations in the same step.

Currently, outputs do not cross the step boundaries.

Matching¶

An output supports an optional match field. The match is used to conditionally create a binding.

In the case of applying a file, for example, the file may contain multiple resources. The match can be used to select the resource to use for creating the binding.

Load an existing resource¶

The example below invokes a kubectl command to get a configmap from the cluster in json format.

The json output is then parsed and added to the $cm binding and the next operation performs an assertion on it by reading the binding instead of querying the cluster.

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  steps:
  - try:
    - script:
        content: kubectl get cm quick-start -n $NAMESPACE -o json
        outputs:
          # parse stdout json output and bind the result to `$cm`
        - name: cm
          value: (json_parse($stdout))
    - assert:
        resource:
          ($cm):
            metadata:
              (uid != null): true

Match a resource¶

The example below applies resources from a file.

When the resource being applied is a configmap, we bind the resource to an output to print its UID in the next operation.

apiVersion: chainsaw.kyverno.io/v1alpha1
kind: Test
metadata:
  name: example
spec:
  steps:
  - try:
    - apply:
        file: ./resources.yaml
        outputs:
          # match the configmap resource and bind it to `$cm`
        - match:
            apiVersion: v1
            kind: ConfigMap
          name: cm
          value: (@)
    - script:
        env:
        - name: UID
          value: ($cm.metadata.uid)
        content: echo $UID

Next step¶

In the next section, we will look at the three main elements of a test step, the try, catch and finally blocks.