package ilm

import "github.com/minio/minio/internal/config"

const (
	transitionWorkers = "transition_workers"
	expirationWorkers = "expiration_workers"
	// EnvILMTransitionWorkers env variable to configure number of transition workers
	EnvILMTransitionWorkers = "MINIO_ILM_TRANSITION_WORKERS"
	// EnvILMExpirationWorkers env variable to configure number of expiration workers

	Filter              Filter              `xml:"Filter,omitempty"`
	Prefix              Prefix              `xml:"Prefix,omitempty"`
	Expiration          Expiration          `xml:"Expiration,omitempty"`
	Transition          Transition          `xml:"Transition,omitempty"`
	DelMarkerExpiration DelMarkerExpiration `xml:"DelMarkerExpiration,omitempty"`

			Optional:    true,
			Type:        "number",
		},
		config.HelpKV{
			Key:         apiTransitionWorkers,
			Description: `set the number of transition workers` + defaultHelpPostfix(apiTransitionWorkers),
			Optional:    true,
			Type:        "number",
		},
		config.HelpKV{
			Key:         apiStaleUploadsExpiry,

func (t *Transition) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
	type transitionWrapper Transition
	var trw transitionWrapper
	err := d.DecodeElement(&trw, &startElement)
	if err != nil {
		return err
	}
	*t = Transition(trw)
	t.set = true
	return nil
}

// Validate - validates the "Transition" element
func (t Transition) Validate() error {
	if !t.set {

			expectedErr: errInvalidStorageClass,
		},
		{
			// no transition rule

		tags[ilmSrc] = src.String()
	}
	tags[ilmAction] = event.Action.String()
	tags[ilmRuleID] = event.RuleID

	if !event.Due.IsZero() {
		tags[ilmDue] = event.Due
	}

	// rule with Transition/NoncurrentVersionTransition in effect
	if event.StorageClass != "" {
		tags[ilmTier] = event.StorageClass
	}

	// rule with NewernoncurrentVersions in effect
	if event.NewerNoncurrentVersions > 0 {

Lifecycle transition rules can be applied to buckets (both versioned and un-versioned) by specifying the tier name defined above as the transition storage class for the lifecycle rule.

## Implementation

		Versioned:        os.Versioned,
		VersionSuspended: os.Suspended,
	}
	if os.Suspended && os.VersionID == "" {
		opts.VersionID = nullVersionID
	}
	return opts
}

// SetTransitionState sets ILM transition related information from given info.
func (os *objSweeper) SetTransitionState(info TransitionedObject) {
	os.TransitionTier = info.Tier
	os.TransitionStatus = info.Status
	os.RemoteObject = info.Name

--restore-request Days=3
```

### 4.1 Monitoring transition events

`s3:ObjectTransition:Complete` and `s3:ObjectTransition:Failed` events can be used to monitor transition events between the source cluster and transition tier. To watch lifecycle events, you can enable bucket notification on the source bucket with `mc event add`  and specify `--event ilm` flag.

Note that transition event notification is a MinIO extension.

## Explore Further

// directed towards a domain other than its own, the remote domain needs to host a cross-domain
// policy file that grants access to the source domain, allowing the client to continue the transaction.
func setCrossDomainPolicyMiddleware(h http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		cxml := crossDomainXML
		if globalServerCtxt.CrossDomainXML != "" {