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Object pruning utility for Go-based Operators

The operator-lib pruning utility lets Go-based Operators clean up, or prune, objects when they are no longer needed. Operator authors can also use the utility to create custom hooks and strategies.

About the operator-lib pruning utility

Objects, such as jobs or pods, are created as a normal part of the Operator life cycle. If the cluster administrator or the Operator does not remove these object, they can stay in the cluster and consume resources.

Previously, the following options were available for pruning unnecessary objects:

  • Operator authors had to create a unique pruning solution for their Operators.

  • Cluster administrators had to clean up objects on their own.

The operator-lib pruning utility removes objects from a Kubernetes cluster for a given namespace. The library was added in version 0.9.0 of the operator-lib library as part of the Operator Framework.

Pruning utility configuration

The operator-lib pruning utility is written in Go and includes common pruning strategies for Go-based Operators.

Example configuration
cfg = Config{
        log:           logf.Log.WithName("prune"),
        DryRun:        false,
        Clientset:     client,
        LabelSelector: "app=<operator_name>",
        Resources: []schema.GroupVersionKind{
                {Group: "", Version: "", Kind: PodKind},
        },
        Namespaces: []string{"<operator_namespace>"},
        Strategy: StrategyConfig{
                Mode:            MaxCountStrategy,
                MaxCountSetting: 1,
        },
        PreDeleteHook: myhook,
}

The pruning utility configuration file defines pruning actions by using the following fields:

Configuration field Description

log

Logger used to handle library log messages.

DryRun

Boolean that determines whether resources should be removed. If set to true, the utility runs but does not to remove resources.

Clientset

Client-go Kubernetes ClientSet used for Kubernetes API calls.

LabelSelector

Kubernetes label selector expression used to find resources to prune.

Resources

Kubernetes resource kinds. PodKind and JobKind are currently supported.

Namespaces

List of Kubernetes namespaces to search for resources.

Strategy

Pruning strategy to run.

Strategy.Mode

MaxCountStrategy, MaxAgeStrategy, or CustomStrategy are currently supported.

Strategy.MaxCountSetting

Integer value for MaxCountStrategy that specifies how many resources should remain after the pruning utility runs.

Strategy.MaxAgeSetting

Go time.Duration string value, such as 48h, that specifies the age of resources to prune.

Strategy.CustomSettings

Go map of values that can be passed into a custom strategy function.

PreDeleteHook

Optional: Go function to call before pruning a resource.

CustomStrategy

Optional: Go function that implements a custom pruning strategy.
Pruning execution

You can call the pruning action by running the execute function on the pruning configuration.

err := cfg.Execute(ctx)

You can also call a pruning action by using a cron package or by calling the pruning utility with a triggering event.