Resource Selector

Part of the command definition is describing the namespace (and cluster, where there is more than one cluster) where the command is executed. The resource you select in the namespace depends on the function of the command.

For example:

If you execute a command on a pod, the command must define how to select that pod.
If you are going to create a new job, the command definition must specify the namespace where the job is created.

Resource selection criteria comes from the namespace and cluster where the command was discovered. See the discussion about command discovery for more information. This by itself can be enough to select the execution namespace.

Resource Selector Configuration Properties describes the properties available for configuring resource selection.

Table 1. Resource Selector Configuration Properties
Property	Description
apiVersion	The Kubernetes API version for the kind of resource to select.
kind	The kind of resource to select.
name	The name of the resource to select.
labels	A map of labels a selected resource must have.
strategy	The strategy to use if more than one matching resource is found. Can be `any` or `all`. The default value is `any`.

The following excerpt shows selection criteria specifying a pod with a given name:

resourceSelector:
  kind: pods
  name: my-pod

The following excerpt shows selection criteria specifying all services with specified labels:

resourceSelector:
  kind: services
  labels:
    app: app-one

The following excerpt shows selection of the current namespace:

resourceSelector: {}

When a resource selector resolves to more than one resource, only one resource is selected for execution by default. Set resourceSelector.strategy to all for execution to occur on all selected resources. If no resources are selected, the command is not executed. For more information, see the discussion about duplicate command behavior.

Note: The Admin Service requires permission to search for resources in the namespace where the command is defined. See the discussion about role-based access control (RBAC) command discovery permissions for more information.

The resource that you select is sometimes dependent on argument and flag values. You can use parameter replacement placeholders in your command definition to resolve at execution time. These placeholders use the ${name} format.

Parameter Replacement Placeholders describes the placeholders that can be used.

Table 2. Parameter Replacement Placeholders
Name	Description
command.flag.`name`	Where `name` is the name of the flag.
command.argument.`name`	Where `name` is the name of the argument.

The following excerpt shows a resource selector added to the hypothetical export command:

command:
  name: export
  description: Export some data
  flags:
    - name: engine
      shortName: e
      type: int
      mandatory: false
      defaultValue: 1
      description: The Engine id
    - name: subdomain
      shortName: s
      type: int
      mandatory: false
      defaultValue: 1
      description: The Subscriber Domain id
resourceSelector:
  kind: services
  labels:
    engineId: ${command.flag.engine}
    subDomainId: ${command.flag.subdomain}