types.go

/*
Copyright 2016 The Kubernetes Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

    http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
*/

package apps

import (
	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
	"k8s.io/apimachinery/pkg/runtime"
	"k8s.io/apimachinery/pkg/util/intstr"
	api "k8s.io/kubernetes/pkg/apis/core"
)

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// StatefulSet represents a set of pods with consistent identities.
// Identities are defined as:
//  - Network: A single stable DNS and hostname.
//  - Storage: As many VolumeClaims as requested.
// The StatefulSet guarantees that a given network identity will always
// map to the same storage identity.
type StatefulSet struct {
	metav1.TypeMeta
	// +optional
	metav1.ObjectMeta

	// Spec defines the desired identities of pods in this set.
	// +optional
	Spec StatefulSetSpec

	// Status is the current status of Pods in this StatefulSet. This data
	// may be out of date by some window of time.
	// +optional
	Status StatefulSetStatus
}

// PodManagementPolicyType defines the policy for creating pods under a stateful set.
type PodManagementPolicyType string

const (
	// OrderedReadyPodManagement will create pods in strictly increasing order on
	// scale up and strictly decreasing order on scale down, progressing only when
	// the previous pod is ready or terminated. At most one pod will be changed
	// at any time.
	OrderedReadyPodManagement PodManagementPolicyType = "OrderedReady"
	// ParallelPodManagement will create and delete pods as soon as the stateful set
	// replica count is changed, and will not wait for pods to be ready or complete
	// termination.
	ParallelPodManagement PodManagementPolicyType = "Parallel"
)

// StatefulSetUpdateStrategy indicates the strategy that the StatefulSet
// controller will use to perform updates. It includes any additional parameters
// necessary to perform the update for the indicated strategy.
type StatefulSetUpdateStrategy struct {
	// Type indicates the type of the StatefulSetUpdateStrategy.
	Type StatefulSetUpdateStrategyType
	// RollingUpdate is used to communicate parameters when Type is RollingUpdateStatefulSetStrategyType.
	RollingUpdate *RollingUpdateStatefulSetStrategy
}

// StatefulSetUpdateStrategyType is a string enumeration type that enumerates
// all possible update strategies for the StatefulSet controller.
type StatefulSetUpdateStrategyType string

const (
	// RollingUpdateStatefulSetStrategyType indicates that update will be
	// applied to all Pods in the StatefulSet with respect to the StatefulSet
	// ordering constraints. When a scale operation is performed with this
	// strategy, new Pods will be created from the specification version indicated
	// by the StatefulSet's updateRevision.
	RollingUpdateStatefulSetStrategyType = "RollingUpdate"
	// OnDeleteStatefulSetStrategyType triggers the legacy behavior. Version
	// tracking and ordered rolling restarts are disabled. Pods are recreated
	// from the StatefulSetSpec when they are manually deleted. When a scale
	// operation is performed with this strategy,specification version indicated
	// by the StatefulSet's currentRevision.
	OnDeleteStatefulSetStrategyType = "OnDelete"
)

// RollingUpdateStatefulSetStrategy is used to communicate parameter for RollingUpdateStatefulSetStrategyType.
type RollingUpdateStatefulSetStrategy struct {
	// Partition indicates the ordinal at which the StatefulSet should be
	// partitioned.
	Partition int32
}

// A StatefulSetSpec is the specification of a StatefulSet.
type StatefulSetSpec struct {
	// Replicas is the desired number of replicas of the given Template.
	// These are replicas in the sense that they are instantiations of the
	// same Template, but individual replicas also have a consistent identity.
	// If unspecified, defaults to 1.
	// TODO: Consider a rename of this field.
	// +optional
	Replicas int32

	// Selector is a label query over pods that should match the replica count.
	// If empty, defaulted to labels on the pod template.
	// More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
	// +optional
	Selector *metav1.LabelSelector

	// Template is the object that describes the pod that will be created if
	// insufficient replicas are detected. Each pod stamped out by the StatefulSet
	// will fulfill this Template, but have a unique identity from the rest
	// of the StatefulSet.
	Template api.PodTemplateSpec

	// VolumeClaimTemplates is a list of claims that pods are allowed to reference.
	// The StatefulSet controller is responsible for mapping network identities to
	// claims in a way that maintains the identity of a pod. Every claim in
	// this list must have at least one matching (by name) volumeMount in one
	// container in the template. A claim in this list takes precedence over
	// any volumes in the template, with the same name.
	// TODO: Define the behavior if a claim already exists with the same name.
	// +optional
	VolumeClaimTemplates []api.PersistentVolumeClaim

	// ServiceName is the name of the service that governs this StatefulSet.
	// This service must exist before the StatefulSet, and is responsible for
	// the network identity of the set. Pods get DNS/hostnames that follow the
	// pattern: pod-specific-string.serviceName.default.svc.cluster.local
	// where "pod-specific-string" is managed by the StatefulSet controller.
	ServiceName string

	// PodManagementPolicy controls how pods are created during initial scale up,
	// when replacing pods on nodes, or when scaling down. The default policy is
	// `OrderedReady`, where pods are created in increasing order (pod-0, then
	// pod-1, etc) and the controller will wait until each pod is ready before
	// continuing. When scaling down, the pods are removed in the opposite order.
	// The alternative policy is `Parallel` which will create pods in parallel
	// to match the desired scale without waiting, and on scale down will delete
	// all pods at once.
	// +optional
	PodManagementPolicy PodManagementPolicyType

	// updateStrategy indicates the StatefulSetUpdateStrategy that will be
	// employed to update Pods in the StatefulSet when a revision is made to
	// Template.
	UpdateStrategy StatefulSetUpdateStrategy

	// revisionHistoryLimit is the maximum number of revisions that will
	// be maintained in the StatefulSet's revision history. The revision history
	// consists of all revisions not represented by a currently applied
	// StatefulSetSpec version. The default value is 10.
	RevisionHistoryLimit *int32
}

// StatefulSetStatus represents the current state of a StatefulSet.
type StatefulSetStatus struct {
	// observedGeneration is the most recent generation observed for this StatefulSet. It corresponds to the
	// StatefulSet's generation, which is updated on mutation by the API Server.
	// +optional
	ObservedGeneration *int64

	// replicas is the number of Pods created by the StatefulSet controller.
	Replicas int32

	// readyReplicas is the number of Pods created by the StatefulSet controller that have a Ready Condition.
	ReadyReplicas int32

	// currentReplicas is the number of Pods created by the StatefulSet controller from the StatefulSet version
	// indicated by currentRevision.
	CurrentReplicas int32

	// updatedReplicas is the number of Pods created by the StatefulSet controller from the StatefulSet version
	// indicated by updateRevision.
	UpdatedReplicas int32

	// currentRevision, if not empty, indicates the version of the StatefulSet used to generate Pods in the
	// sequence [0,currentReplicas).
	CurrentRevision string

	// updateRevision, if not empty, indicates the version of the StatefulSet used to generate Pods in the sequence
	// [replicas-updatedReplicas,replicas)
	UpdateRevision string

	// collisionCount is the count of hash collisions for the StatefulSet. The StatefulSet controller
	// uses this field as a collision avoidance mechanism when it needs to create the name for the
	// newest ControllerRevision.
	// +optional
	CollisionCount *int32

	// Represents the latest available observations of a statefulset's current state.
	Conditions []StatefulSetCondition
}

type StatefulSetConditionType string

// TODO: Add valid condition types for Statefulsets.

// StatefulSetCondition describes the state of a statefulset at a certain point.
type StatefulSetCondition struct {
	// Type of statefulset condition.
	Type StatefulSetConditionType
	// Status of the condition, one of True, False, Unknown.
	Status api.ConditionStatus
	// The last time this condition was updated.
	LastTransitionTime metav1.Time
	// The reason for the condition's last transition.
	Reason string
	// A human readable message indicating details about the transition.
	Message string
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// StatefulSetList is a collection of StatefulSets.
type StatefulSetList struct {
	metav1.TypeMeta
	// +optional
	metav1.ListMeta
	Items []StatefulSet
}

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// ControllerRevision implements an immutable snapshot of state data. Clients
// are responsible for serializing and deserializing the objects that contain
// their internal state.
// Once a ControllerRevision has been successfully created, it can not be updated.
// The API Server will fail validation of all requests that attempt to mutate
// the Data field. ControllerRevisions may, however, be deleted.
type ControllerRevision struct {
	metav1.TypeMeta
	// Standard object's metadata.
	// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
	// +optional
	metav1.ObjectMeta

	// Data is the Object representing the state.
	Data runtime.Object

	// Revision indicates the revision of the state represented by Data.
	Revision int64
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// ControllerRevisionList is a resource containing a list of ControllerRevision objects.
type ControllerRevisionList struct {
	metav1.TypeMeta
	// +optional
	metav1.ListMeta

	// Items is the list of ControllerRevision objects.
	Items []ControllerRevision
}

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type Deployment struct {
	metav1.TypeMeta
	// +optional
	metav1.ObjectMeta

	// Specification of the desired behavior of the Deployment.
	// +optional
	Spec DeploymentSpec

	// Most recently observed status of the Deployment.
	// +optional
	Status DeploymentStatus
}

type DeploymentSpec struct {
	// Number of desired pods. This is a pointer to distinguish between explicit
	// zero and not specified. Defaults to 1.
	// +optional
	Replicas int32

	// Label selector for pods. Existing ReplicaSets whose pods are
	// selected by this will be the ones affected by this deployment.
	// +optional
	Selector *metav1.LabelSelector

	// Template describes the pods that will be created.
	Template api.PodTemplateSpec

	// The deployment strategy to use to replace existing pods with new ones.
	// +optional
	Strategy DeploymentStrategy

	// Minimum number of seconds for which a newly created pod should be ready
	// without any of its container crashing, for it to be considered available.
	// Defaults to 0 (pod will be considered available as soon as it is ready)
	// +optional
	MinReadySeconds int32

	// The number of old ReplicaSets to retain to allow rollback.
	// This is a pointer to distinguish between explicit zero and not specified.
	// This is set to the max value of int32 (i.e. 2147483647) by default, which means
	// "retaining all old ReplicaSets".
	// +optional
	RevisionHistoryLimit *int32

	// Indicates that the deployment is paused and will not be processed by the
	// deployment controller.
	// +optional
	Paused bool

	// DEPRECATED.
	// The config this deployment is rolling back to. Will be cleared after rollback is done.
	// +optional
	RollbackTo *RollbackConfig

	// The maximum time in seconds for a deployment to make progress before it
	// is considered to be failed. The deployment controller will continue to
	// process failed deployments and a condition with a ProgressDeadlineExceeded
	// reason will be surfaced in the deployment status. Note that progress will
	// not be estimated during the time a deployment is paused. This is set to
	// the max value of int32 (i.e. 2147483647) by default, which means "no deadline".
	// +optional
	ProgressDeadlineSeconds *int32
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// DEPRECATED.
// DeploymentRollback stores the information required to rollback a deployment.
type DeploymentRollback struct {
	metav1.TypeMeta
	// Required: This must match the Name of a deployment.
	Name string
	// The annotations to be updated to a deployment
	// +optional
	UpdatedAnnotations map[string]string
	// The config of this deployment rollback.
	RollbackTo RollbackConfig
}

// DEPRECATED.
type RollbackConfig struct {
	// The revision to rollback to. If set to 0, rollback to the last revision.
	// +optional
	Revision int64
}

const (
	// DefaultDeploymentUniqueLabelKey is the default key of the selector that is added
	// to existing RCs (and label key that is added to its pods) to prevent the existing RCs
	// to select new pods (and old pods being select by new RC).
	DefaultDeploymentUniqueLabelKey string = "pod-template-hash"
)

type DeploymentStrategy struct {
	// Type of deployment. Can be "Recreate" or "RollingUpdate". Default is RollingUpdate.
	// +optional
	Type DeploymentStrategyType

	// Rolling update config params. Present only if DeploymentStrategyType =
	// RollingUpdate.
	//---
	// TODO: Update this to follow our convention for oneOf, whatever we decide it
	// to be.
	// +optional
	RollingUpdate *RollingUpdateDeployment
}

type DeploymentStrategyType string

const (
	// RecreateDeploymentStrategyType - kill all existing pods before creating new ones.
	RecreateDeploymentStrategyType DeploymentStrategyType = "Recreate"

	// RollingUpdateDeploymentStrategyType - Replace the old RCs by new one using rolling update i.e gradually scale down the old RCs and scale up the new one.
	RollingUpdateDeploymentStrategyType DeploymentStrategyType = "RollingUpdate"
)

// RollingUpdateDeployment is the spec to control the desired behavior of rolling update.
type RollingUpdateDeployment struct {
	// The maximum number of pods that can be unavailable during the update.
	// Value can be an absolute number (ex: 5) or a percentage of total pods at the start of update (ex: 10%).
	// Absolute number is calculated from percentage by rounding down.
	// This can not be 0 if MaxSurge is 0.
	// By default, a fixed value of 1 is used.
	// Example: when this is set to 30%, the old RC can be scaled down by 30%
	// immediately when the rolling update starts. Once new pods are ready, old RC
	// can be scaled down further, followed by scaling up the new RC, ensuring
	// that at least 70% of original number of pods are available at all times
	// during the update.
	// +optional
	MaxUnavailable intstr.IntOrString

	// The maximum number of pods that can be scheduled above the original number of
	// pods.
	// Value can be an absolute number (ex: 5) or a percentage of total pods at
	// the start of the update (ex: 10%). This can not be 0 if MaxUnavailable is 0.
	// Absolute number is calculated from percentage by rounding up.
	// By default, a value of 1 is used.
	// Example: when this is set to 30%, the new RC can be scaled up by 30%
	// immediately when the rolling update starts. Once old pods have been killed,
	// new RC can be scaled up further, ensuring that total number of pods running
	// at any time during the update is at most 130% of original pods.
	// +optional
	MaxSurge intstr.IntOrString
}

type DeploymentStatus struct {
	// The generation observed by the deployment controller.
	// +optional
	ObservedGeneration int64

	// Total number of non-terminated pods targeted by this deployment (their labels match the selector).
	// +optional
	Replicas int32

	// Total number of non-terminated pods targeted by this deployment that have the desired template spec.
	// +optional
	UpdatedReplicas int32

	// Total number of ready pods targeted by this deployment.
	// +optional
	ReadyReplicas int32

	// Total number of available pods (ready for at least minReadySeconds) targeted by this deployment.
	// +optional
	AvailableReplicas int32

	// Total number of unavailable pods targeted by this deployment. This is the total number of
	// pods that are still required for the deployment to have 100% available capacity. They may
	// either be pods that are running but not yet available or pods that still have not been created.
	// +optional
	UnavailableReplicas int32

	// Represents the latest available observations of a deployment's current state.
	Conditions []DeploymentCondition

	// Count of hash collisions for the Deployment. The Deployment controller uses this
	// field as a collision avoidance mechanism when it needs to create the name for the
	// newest ReplicaSet.
	// +optional
	CollisionCount *int32
}

type DeploymentConditionType string

// These are valid conditions of a deployment.
const (
	// Available means the deployment is available, ie. at least the minimum available
	// replicas required are up and running for at least minReadySeconds.
	DeploymentAvailable DeploymentConditionType = "Available"
	// Progressing means the deployment is progressing. Progress for a deployment is
	// considered when a new replica set is created or adopted, and when new pods scale
	// up or old pods scale down. Progress is not estimated for paused deployments or
	// when progressDeadlineSeconds is not specified.
	DeploymentProgressing DeploymentConditionType = "Progressing"
	// ReplicaFailure is added in a deployment when one of its pods fails to be created
	// or deleted.
	DeploymentReplicaFailure DeploymentConditionType = "ReplicaFailure"
)

// DeploymentCondition describes the state of a deployment at a certain point.
type DeploymentCondition struct {
	// Type of deployment condition.
	Type DeploymentConditionType
	// Status of the condition, one of True, False, Unknown.
	Status api.ConditionStatus
	// The last time this condition was updated.
	LastUpdateTime metav1.Time
	// Last time the condition transitioned from one status to another.
	LastTransitionTime metav1.Time
	// The reason for the condition's last transition.
	Reason string
	// A human readable message indicating details about the transition.
	Message string
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

type DeploymentList struct {
	metav1.TypeMeta
	// +optional
	metav1.ListMeta

	// Items is the list of deployments.
	Items []Deployment
}

type DaemonSetUpdateStrategy struct {
	// Type of daemon set update. Can be "RollingUpdate" or "OnDelete".
	// Default is OnDelete.
	// +optional
	Type DaemonSetUpdateStrategyType

	// Rolling update config params. Present only if type = "RollingUpdate".
	//---
	// TODO: Update this to follow our convention for oneOf, whatever we decide it
	// to be. Same as Deployment `strategy.rollingUpdate`.
	// See https://github.com/kubernetes/kubernetes/issues/35345
	// +optional
	RollingUpdate *RollingUpdateDaemonSet
}

type DaemonSetUpdateStrategyType string

const (
	// RollingUpdateDaemonSetStrategyType - Replace the old daemons by new ones using rolling update i.e replace them on each node one after the other.
	RollingUpdateDaemonSetStrategyType DaemonSetUpdateStrategyType = "RollingUpdate"

	// OnDeleteDaemonSetStrategyType - Replace the old daemons only when it's killed
	OnDeleteDaemonSetStrategyType DaemonSetUpdateStrategyType = "OnDelete"
)

// RollingUpdateDaemonSet is the spec to control the desired behavior of daemon set rolling update.
type RollingUpdateDaemonSet struct {
	// The maximum number of DaemonSet pods that can be unavailable during the
	// update. Value can be an absolute number (ex: 5) or a percentage of total
	// number of DaemonSet pods at the start of the update (ex: 10%). Absolute
	// number is calculated from percentage by rounding up.
	// This cannot be 0.
	// Default value is 1.
	// Example: when this is set to 30%, at most 30% of the total number of nodes
	// that should be running the daemon pod (i.e. status.desiredNumberScheduled)
	// can have their pods stopped for an update at any given
	// time. The update starts by stopping at most 30% of those DaemonSet pods
	// and then brings up new DaemonSet pods in their place. Once the new pods
	// are available, it then proceeds onto other DaemonSet pods, thus ensuring
	// that at least 70% of original number of DaemonSet pods are available at
	// all times during the update.
	// +optional
	MaxUnavailable intstr.IntOrString
}

// DaemonSetSpec is the specification of a daemon set.
type DaemonSetSpec struct {
	// A label query over pods that are managed by the daemon set.
	// Must match in order to be controlled.
	// If empty, defaulted to labels on Pod template.
	// More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
	// +optional
	Selector *metav1.LabelSelector

	// An object that describes the pod that will be created.
	// The DaemonSet will create exactly one copy of this pod on every node
	// that matches the template's node selector (or on every node if no node
	// selector is specified).
	// More info: https://kubernetes.io/docs/concepts/workloads/controllers/replicationcontroller#pod-template
	Template api.PodTemplateSpec

	// An update strategy to replace existing DaemonSet pods with new pods.
	// +optional
	UpdateStrategy DaemonSetUpdateStrategy

	// The minimum number of seconds for which a newly created DaemonSet pod should
	// be ready without any of its container crashing, for it to be considered
	// available. Defaults to 0 (pod will be considered available as soon as it
	// is ready).
	// +optional
	MinReadySeconds int32

	// DEPRECATED.
	// A sequence number representing a specific generation of the template.
	// Populated by the system. It can be set only during the creation.
	// +optional
	TemplateGeneration int64

	// The number of old history to retain to allow rollback.
	// This is a pointer to distinguish between explicit zero and not specified.
	// Defaults to 10.
	// +optional
	RevisionHistoryLimit *int32
}

// DaemonSetStatus represents the current status of a daemon set.
type DaemonSetStatus struct {
	// The number of nodes that are running at least 1
	// daemon pod and are supposed to run the daemon pod.
	CurrentNumberScheduled int32

	// The number of nodes that are running the daemon pod, but are
	// not supposed to run the daemon pod.
	NumberMisscheduled int32

	// The total number of nodes that should be running the daemon
	// pod (including nodes correctly running the daemon pod).
	DesiredNumberScheduled int32

	// The number of nodes that should be running the daemon pod and have one
	// or more of the daemon pod running and ready.
	NumberReady int32

	// The most recent generation observed by the daemon set controller.
	// +optional
	ObservedGeneration int64

	// The total number of nodes that are running updated daemon pod
	// +optional
	UpdatedNumberScheduled int32

	// The number of nodes that should be running the
	// daemon pod and have one or more of the daemon pod running and
	// available (ready for at least spec.minReadySeconds)
	// +optional
	NumberAvailable int32

	// The number of nodes that should be running the
	// daemon pod and have none of the daemon pod running and available
	// (ready for at least spec.minReadySeconds)
	// +optional
	NumberUnavailable int32

	// Count of hash collisions for the DaemonSet. The DaemonSet controller
	// uses this field as a collision avoidance mechanism when it needs to
	// create the name for the newest ControllerRevision.
	// +optional
	CollisionCount *int32

	// Represents the latest available observations of a DaemonSet's current state.
	Conditions []DaemonSetCondition
}

type DaemonSetConditionType string

// TODO: Add valid condition types of a DaemonSet.

// DaemonSetCondition describes the state of a DaemonSet at a certain point.
type DaemonSetCondition struct {
	// Type of DaemonSet condition.
	Type DaemonSetConditionType
	// Status of the condition, one of True, False, Unknown.
	Status api.ConditionStatus
	// Last time the condition transitioned from one status to another.
	LastTransitionTime metav1.Time
	// The reason for the condition's last transition.
	Reason string
	// A human readable message indicating details about the transition.
	Message string
}

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// DaemonSet represents the configuration of a daemon set.
type DaemonSet struct {
	metav1.TypeMeta
	// Standard object's metadata.
	// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
	// +optional
	metav1.ObjectMeta

	// The desired behavior of this daemon set.
	// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status
	// +optional
	Spec DaemonSetSpec

	// The current status of this daemon set. This data may be
	// out of date by some window of time.
	// Populated by the system.
	// Read-only.
	// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#spec-and-status
	// +optional
	Status DaemonSetStatus
}

const (
	// DEPRECATED: DefaultDaemonSetUniqueLabelKey is used instead.
	// DaemonSetTemplateGenerationKey is the key of the labels that is added
	// to daemon set pods to distinguish between old and new pod templates
	// during DaemonSet template update.
	DaemonSetTemplateGenerationKey string = "pod-template-generation"
)

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// DaemonSetList is a collection of daemon sets.
type DaemonSetList struct {
	metav1.TypeMeta
	// Standard list metadata.
	// More info: https://git.k8s.io/community/contributors/devel/api-conventions.md#metadata
	// +optional
	metav1.ListMeta

	// A list of daemon sets.
	Items []DaemonSet
}

// +genclient
// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// ReplicaSet ensures that a specified number of pod replicas are running at any given time.
type ReplicaSet struct {
	metav1.TypeMeta
	// +optional
	metav1.ObjectMeta

	// Spec defines the desired behavior of this ReplicaSet.
	// +optional
	Spec ReplicaSetSpec

	// Status is the current status of this ReplicaSet. This data may be
	// out of date by some window of time.
	// +optional
	Status ReplicaSetStatus
}

// +k8s:deepcopy-gen:interfaces=k8s.io/apimachinery/pkg/runtime.Object

// ReplicaSetList is a collection of ReplicaSets.
type ReplicaSetList struct {
	metav1.TypeMeta
	// +optional
	metav1.ListMeta

	Items []ReplicaSet
}

// ReplicaSetSpec is the specification of a ReplicaSet.
// As the internal representation of a ReplicaSet, it must have
// a Template set.
type ReplicaSetSpec struct {
	// Replicas is the number of desired replicas.
	Replicas int32

	// Minimum number of seconds for which a newly created pod should be ready
	// without any of its container crashing, for it to be considered available.
	// Defaults to 0 (pod will be considered available as soon as it is ready)
	// +optional
	MinReadySeconds int32

	// Selector is a label query over pods that should match the replica count.
	// Must match in order to be controlled.
	// If empty, defaulted to labels on pod template.
	// More info: https://kubernetes.io/docs/concepts/overview/working-with-objects/labels/#label-selectors
	// +optional
	Selector *metav1.LabelSelector

	// Template is the object that describes the pod that will be created if
	// insufficient replicas are detected.
	// +optional
	Template api.PodTemplateSpec
}

// ReplicaSetStatus represents the current status of a ReplicaSet.
type ReplicaSetStatus struct {
	// Replicas is the number of actual replicas.
	Replicas int32

	// The number of pods that have labels matching the labels of the pod template of the replicaset.
	// +optional
	FullyLabeledReplicas int32

	// The number of ready replicas for this replica set.
	// +optional
	ReadyReplicas int32

	// The number of available replicas (ready for at least minReadySeconds) for this replica set.
	// +optional
	AvailableReplicas int32

	// ObservedGeneration is the most recent generation observed by the controller.
	// +optional
	ObservedGeneration int64

	// Represents the latest available observations of a replica set's current state.
	// +optional
	Conditions []ReplicaSetCondition
}

type ReplicaSetConditionType string

// These are valid conditions of a replica set.
const (
	// ReplicaSetReplicaFailure is added in a replica set when one of its pods fails to be created
	// due to insufficient quota, limit ranges, pod security policy, node selectors, etc. or deleted
	// due to kubelet being down or finalizers are failing.
	ReplicaSetReplicaFailure ReplicaSetConditionType = "ReplicaFailure"
)

// ReplicaSetCondition describes the state of a replica set at a certain point.
type ReplicaSetCondition struct {
	// Type of replica set condition.
	Type ReplicaSetConditionType
	// Status of the condition, one of True, False, Unknown.
	Status api.ConditionStatus
	// The last time the condition transitioned from one status to another.
	// +optional
	LastTransitionTime metav1.Time
	// The reason for the condition's last transition.
	// +optional
	Reason string
	// A human readable message indicating details about the transition.
	// +optional
	Message string
}