feat: scheduled custom resource

[AmitKumarDas]

litmuschaos/litmus#1223

[AmitKumarDas]

Draft Design

// ScheduleType is a typed definition to determine the type
// of a schedule
type ScheduleType string

const (
	// ScheduleTypeRepeat creates & deletes the resource
	// repeatedly based on schedule specifications
	ScheduleTypeRepeat ScheduleType = "Repeat"

	// ScheduleTypeHourly creates & deletes the resource
	// once every hour
	ScheduleTypeHourly ScheduleType = "Hourly"

	// ScheduleTypeDaily creates & deletes the resource
	// once everyday
	ScheduleTypeDaily ScheduleType = "Daily"

	// ScheduleTypeWeekly creates & deletes the resource
	// once every week
	ScheduleTypeWeekly ScheduleType = "Weekly"

	// ScheduleTypeOnce triggers creation & deletion of the
	// the target resource only once at a specific time in
	// the lifetime of this CronResource
	ScheduleTypeOnce ScheduleType = "Once"

	// ScheduleTypeImmediately triggers creation & deletion
	// of the the target resource immediately & then as
	// specified in the schedule specifications
	ScheduleTypeImmediately ScheduleType = "Immediately"

	// ScheduleTypeImmediatelyOnce triggers creation & deletion
	// of the the target resource immediately & only once in the
	// lifetime of this CronResource
	ScheduleTypeImmediatelyOnce ScheduleType = "ImmediatelyOnce"
)

// ScheduleDay is a typed definition to define supported
// days to schedule a resource
type ScheduleDay string

const (
	// ScheduleDayEveryday represents all days as supported
	// schedule days
	ScheduleDayEveryday ScheduleDay = "Everyday"

	// ScheduleDaySun represents Sunday as a supported schedule day
	ScheduleDaySun ScheduleDay = "Sun"

	// ScheduleDaySunday represents Sunday as a supported schedule day
	ScheduleDaySunday ScheduleDay = "Sunday"

	// ScheduleDayMon represents Monday as a supported schedule day
	ScheduleDayMon ScheduleDay = "Mon"

	// ScheduleDayMonday represents Monday as a supported schedule day
	ScheduleDayMonday ScheduleDay = "Monday"

	// ScheduleDayTue represents Tuesday as a supported schedule day
	ScheduleDayTue ScheduleDay = "Tue"

	// ScheduleDayTuesday represents Tuesday as a supported schedule day
	ScheduleDayTuesday ScheduleDay = "Tuesday"

	// ScheduleDayWed represents Wednesday as a supported schedule day
	ScheduleDayWed ScheduleDay = "Wed"

	// ScheduleDayWednesday represents Wednesday as a supported schedule day
	ScheduleDayWednesday ScheduleDay = "Wednesday"

	// ScheduleDayThu represents Thursday as a supported schedule day
	ScheduleDayThu ScheduleDay = "Thu"

	// ScheduleDayThursday represents Thursday as a supported schedule day
	ScheduleDayThursday ScheduleDay = "Thursday"

	// ScheduleDayFri represents Friday as a supported schedule day
	ScheduleDayFri ScheduleDay = "Fri"

	// ScheduleDayFriday represents Friday as a supported schedule day
	ScheduleDayFriday ScheduleDay = "Friday"

	// ScheduleDaySat represents Saturday as a supported schedule day
	ScheduleDaySat ScheduleDay = "Sat"

	// ScheduleDaySaturday represents Saturday as a supported schedule day
	ScheduleDaySaturday ScheduleDay = "Saturday"
)

// CronResource is a kubernetes custom resource that defines
// the specifications to create & delete any kubernetes resource
// at specified intervals
type CronResource struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata"`

	Spec CronResourceSpec `json:"spec"`
}

// CronResourceSpec defines the configuration required
// to create & delete a kubernetes resource at specified intervals
type CronResourceSpec struct {
	// Supend indicates if all operations of this cron
	// schedule should be stopped. The relevant resources
	// created due to CronResource should be deleted.
	Suspend *bool `json:"suspend,omitempty"`

	// CompletionCriteria can be specified to mark the
	// current schedule as completed or not
	CompletionCriteria CronResourceCompletionCriteria `json:"completionCriteria,omitempty"`

	// Schedule to be followed for this CronResource
	Schedule CronResourceSchedule `json:"schedule,omitempty"`

	// Template has the desired state of the resource that
	// needs to be created or deleted as part of CronResource
	// schedule
	Template CronResourceTemplateReference `json:"template,omitempty"`
}

// CronResourceSchedule provides the schedule details that the
// entire CronResource reconciliation is based on
type CronResourceSchedule struct {
	// ScheduleType provides the frequency of this schedule
	//
	// Defaults to Hourly schedule
	ScheduleType ScheduleType `json:"scheduleType,omitempty"`

	// Time to start the schedule. In other words, post this
	// time schedule get activated.
	//
	// StartTime is optional
	StartTime metav1.Time `json:"startTime,omitempty"`

	// Time to end the schedule. Post this time resources created
	// due to this CronResource will get deleted.
	//
	// EndTime is optional
	EndTime metav1.Time `json:"endTime,omitempty"`

	// RepeatInterval indicates the interval post which a new
	// schedule instance gets triggered. In other words post
	// this interval the existing resource created due to the
	// schedule gets deleted & a new resource takes its place.
	// The repeat interval is ignored if existing resource is
	// not completed.
	//
	// RepeatInterval is used for ScheduleType **Repeat**
	//
	// RepeatInterval is optional & defaults to 1 hour if
	// ScheduleType is Repeat
	RepeatInterval time.Duration `json:"repeatInterval,omitempty"`

	// RepeatCount provides the maximum number of times a schedule
	// instance gets triggered
	//
	// If MaxCount is 5 and ScheduleType is Daily then, this
	// CronResource is supposed to run only for the next 5 days
	// with each new schedule occuring after 24 hours.
	//
	// RepeatCount is optional
	MaxCount *int `json:"maxCount,omitempty"`

	// Replicas / InstanceCount ?
	// cc @karthik can you clarify ?
	Replicas *int `json:"replicas,omitempty"`

	// EligibleDays provides the list of days that are eligible
	// to run this schedule. If there are any resources left due
	// to an earlier schedule on a non-eligible day, then this
	// resource gets deleted. No new resource will get created
	// on a non-eligible day.
	//
	// EligibleDays provides an extra filter to evaluate if
	// CronResource should be run or not.
	//
	// EligibleDays is optional & marks every day as eligible to
	// run this schedule
	EligibleDays []ScheduleDay `json:"eligibleDays,omitempty"`
}

// CronResourceCompletionCriteria is used to mark a CronResource
// schedule as completed or not
type CronResourceCompletionCriteria struct {
	// Select terms applied over the resource to mark the
	// current schedule as complete
	Selector metac.ResourceSelector `json:"selector,omitempty"`

	// Timeout indicates the time taken after which the
	// current schedule can be marked as completed
	Timeout time.Duration `json:"timeout,omitempty"`
}

// CronResourceTemplateReference provides the reference to the
// resource state or object or both. This is the resource that
// gets created & deleted as part of CronResource reconciliation.
type CronResourceTemplateReference struct {
	// Desired state that gets created & deleted as part of
	// CronResource reconciliation. This state can be in partial
	// form which in turn gets applied against the specifications
	// found in ObjectReference to arrive at the full resource
	// specs.
	//
	// NOTE:
	// - State is optional
	// - Both State & ObjectReference can not be empty
	// - Both State & ObjectReference can be set in a CronResource
	State map[string]interface{} `json:"state,omitempty"`

	// Resource instance has the resource state that gets created
	// & deleted as part of CronResource reconciliation
	//
	// NOTE:
	// - ObjectReference is optional
	// - Both ObjectReference & State can not be empty
	// - Both ObjectReference & State can be set in a CronResource
	ObjectReference CronResourceTemplateObjectReference `json:"objectReference,omitempty"`
}

// CronResourceTemplateObjectReference refers to the resource
// observed in the cluster that will be created & deleted as
// part of CronResource reconciliation
type CronResourceTemplateObjectReference struct {
	Name      string `json:"objectName"`
	Namespace string `json:"objectNamespace"`
}

// CronResourceTemplate is the placeholder for desired or default
// state of resource that gets created & deleted as part of
// CronResource reconciliation. This is a custom resource that can
// be applied separately against the kubernetes cluster.
type CronResourceTemplate struct {
	metav1.TypeMeta   `json:",inline"`
	metav1.ObjectMeta `json:"metadata"`

	Spec CronResourceTemplateSpec `json:"spec"`
}

// CronResourceTemplateSpec refers to the desired or default
// state of the resource that gets created & deleted as part
// of CronResource reconciliation
type CronResourceTemplateSpec struct {
	// State represents the desired state of the resource
	// that gets created & deleted as part of CronResource
	// reconciliation.
	State map[string]interface{} `json:"state,omitempty"`
}