pod_disruption_budget.go

// Copyright 2021 - 2024 Crunchy Data Solutions, Inc.
//
// SPDX-License-Identifier: Apache-2.0

package postgrescluster

// Note: The behavior for an empty selector differs between the
// policy/v1beta1 and policy/v1 APIs for PodDisruptionBudgets. For
// policy/v1beta1 an empty selector matches zero pods, while for
// policy/v1 an empty selector matches every pod in the namespace.
// https://kubernetes.io/docs/tasks/run-application/configure-pdb/#specifying-a-poddisruptionbudget
import (
	"github.com/pkg/errors"
	policyv1 "k8s.io/api/policy/v1"
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/util/intstr"

	"github.com/percona/percona-postgresql-operator/internal/initialize"
	"github.com/percona/percona-postgresql-operator/pkg/apis/postgres-operator.crunchydata.com/v1beta1"
)

// generatePodDisruptionBudget takes parameters required to fill out a PDB and
// returns the PDB
func (r *Reconciler) generatePodDisruptionBudget(
	cluster *v1beta1.PostgresCluster,
	meta metav1.ObjectMeta,
	minAvailable *intstr.IntOrString,
	selector metav1.LabelSelector,
) (*policyv1.PodDisruptionBudget, error) {
	pdb := &policyv1.PodDisruptionBudget{
		ObjectMeta: meta,
		Spec: policyv1.PodDisruptionBudgetSpec{
			MinAvailable: minAvailable,
			Selector:     &selector,
		},
	}
	pdb.SetGroupVersionKind(policyv1.SchemeGroupVersion.WithKind("PodDisruptionBudget"))
	err := errors.WithStack(r.setControllerReference(cluster, pdb))
	return pdb, err
}

// getMinAvailable contains logic to either parse a user provided IntOrString
// value or determine a default minimum available based on replicas. In both
// cases it returns the minAvailable as an int32 that should be set on a
// PodDisruptionBudget
func getMinAvailable(
	minAvailable *intstr.IntOrString,
	replicas int32,
) *intstr.IntOrString {
	// TODO: Webhook Validation for minAvailable in the spec
	// - MinAvailable should be less than replicas
	// - MinAvailable as a string value should be a percentage string <= 100%
	if minAvailable != nil {
		return minAvailable
	}

	// If the user does not provide 'minAvailable', we will set a default
	// based on the number of replicas.
	var expect int32

	// We default to '1' if they have more than one replica defined.
	if replicas > 1 {
		expect = 1
	}

	// If more than one replica is not defined, we will default to '0'
	return initialize.Pointer(intstr.FromInt32(expect))
}