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Concepts for Package Consumers

Namespacing

Overview

In the packaging APIs, all the CRs are namespaced, which can create a lot of duplication when wanting to share packages across the cluster. To account for this, kapp-controller accepts a flag -packaging-global-namespace, which configures kapp-controller to treat the provided namespace as a global namespace for packaging resources. This means any Package and PackageMetadata CRs within that namespace will be included in all other namespaces on the cluster, without duplicating them. This does not apply to PackageRepositories or PackageInstalls.

Collisions

When there is a conflict, the locally namespaced resources will take precedence over the global ones. A conflict for Packages is defined as having the same spec.refName and spec.version, while for PackageMetadatas it is defined as having the same metadata.name. For example, if there is a globally available PackageMetadata created from the following YAML:

---
apiVersion: data.packaging.carvel.dev/v1alpha1
kind: PackageMetadata
metadata:
  name: simple-app.corp.com
  namespace: <global-namespace>
spec:
  categories:
  - demo
  displayName: Simple App
  longDescription: Simple app consisting of a k8s deployment and service
  shortDescription: Simple app for demoing

and then a new locally available PackageMetadata is created from this YAML,

---
apiVersion: data.packaging.carvel.dev/v1alpha1
kind: PackageMetadata
metadata:
  name: simple-app.corp.com
  namespace: <local-namespace>
spec:
  categories:
  - demo
  displayName: Simple App Override
  longDescription: My locally available version of the Simple App package
  shortDescription: Simple App with some edits

a user listing the PackageMetadatas will see the second CR, and not the first.

Annotations

For client discoverability, the namespace should also be present as an annotation on the PackageRepository CRD under the packaging.carvel.dev/global-namespace. Kapp controller’s release YAML comes preconfigured with this annotation.

(upcoming) If users would like to exclude the global packages from their namespace, the annotation packaging.carvel.dev/exclude-global-packages can be added to the namespace.

Using PackageInstall’s Version Selection

The following sections cover aspects of how to approach version selection when using PackageInstalls.

Constraints

PackageInstalls offer a property called constraints under .spec.packageRef.versionSelection. This constraints property can be used to select a specific version of a Package CR to install or include a set of conditions to pick a version. This constraints property is based on semver ranges and more details on conditions that can be included with constraints can be found here.

To select a specific version of a Package CR to use with a PackageInstall, the full version (i.e. .spec.version from a Package CR) can be included in the constraints property, such as what is shown below:

packageRef:
  refName: fluent-bit.vmware.com
  versionSelection:
    constraints: "1.5.3"

The example above will result in version 1.5.3 of the Package being installed.

An example of using a condition to select a Package CR with constraints is shown below:

packageRef:
  refName: fluent-bit.vmware.com
  versionSelection:
    constraints: ">1.5.3"

The above constraint will result in any version greater than 1.5.3 of the Package being installed. It will also automatically update to the latest versions of the Package as they become available on the cluster.

Prereleases

When creating a PackageInstall, by default prereleases are not included by kapp-controller when considering which versions of a Package CR to install. To include prereleases when creating a PackageInstall, the following can be added to the spec:

versionSelection:
  constraints: "3.0.0-rc.1"
  prereleases: {}

Specifying prereleases: {} will make kapp-controller consider all available prereleases when seeing if a Package CR is available to be installed.

To filter by releases containing certain substrings, there is an identifiers property under prereleases that can be used to only include certain prereleases that contain the identifier, such as what is shown below:

versionSelection:
  constraints: "3.0.0"
  prereleases:
    identifiers: [rc]

Multiple identifiers can be specified to include multiple types of pre-releases (e.g. identifiers: [rc, beta]).

Downgrading

In v0.25.0+ of kapp-controller, PackageInstalls feature an annotation to allow PackageInstalls to be downgraded to previous versions of a Package. By default, kapp-controller does not allow downgrading to a previous version of a Package to protect against certain scenarios (e.g. the latest version of a Package being removed resulting in a unintended reconciliation where the PackageInstall picks up a lower Package version that is now the latest version).

If downgrading to a previous version is desired, adding the annotation packaging.carvel.dev/downgradable: "" to a PackageInstall will allow for explicit or automated ways of downgrading the PackageInstall to a lower version.

---
apiVersion: packaging.carvel.dev/v1alpha1
kind: PackageInstall
metadata:
  name: pkg-demo
  annotations:
    packaging.carvel.dev/downgradable: ""
spec:
  packageRef:
    refName: simple-app.corp.com
    versionSelection:
      constraints: >=1.0.0