Add support for ILM transition (#10565)

This PR adds transition support for ILM
to transition data to another MinIO target
represented by a storage class ARN. Subsequent
GET or HEAD for that object will be streamed from
the transition tier. If PostRestoreObject API is
invoked, the transitioned object can be restored for
duration specified to the source cluster.

pkg/bucket/lifecycle/transition.go

@@ -18,25 +18,147 @@ package lifecycle
 
 import (
 	"encoding/xml"
+	"time"
 )
 
+var (
+	errTransitionInvalidDays     = Errorf("Days must be 0 or greater when used with Transition")
+	errTransitionInvalidDate     = Errorf("Date must be provided in ISO 8601 format")
+	errTransitionInvalid         = Errorf("Exactly one of Days (0 or greater) or Date (positive ISO 8601 format) should be present inside Expiration.")
+	errTransitionDateNotMidnight = Errorf("'Date' must be at midnight GMT")
+)
+
+// TransitionDate is a embedded type containing time.Time to unmarshal
+// Date in Transition
+type TransitionDate struct {
+	time.Time
+}
+
+// UnmarshalXML parses date from Transition and validates date format
+func (tDate *TransitionDate) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
+	var dateStr string
+	err := d.DecodeElement(&dateStr, &startElement)
+	if err != nil {
+		return err
+	}
+	// While AWS documentation mentions that the date specified
+	// must be present in ISO 8601 format, in reality they allow
+	// users to provide RFC 3339 compliant dates.
+	trnDate, err := time.Parse(time.RFC3339, dateStr)
+	if err != nil {
+		return errTransitionInvalidDate
+	}
+	// Allow only date timestamp specifying midnight GMT
+	hr, min, sec := trnDate.Clock()
+	nsec := trnDate.Nanosecond()
+	loc := trnDate.Location()
+	if !(hr == 0 && min == 0 && sec == 0 && nsec == 0 && loc.String() == time.UTC.String()) {
+		return errTransitionDateNotMidnight
+	}
+
+	*tDate = TransitionDate{trnDate}
+	return nil
+}
+
+// MarshalXML encodes expiration date if it is non-zero and encodes
+// empty string otherwise
+func (tDate TransitionDate) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
+	if tDate.Time.IsZero() {
+		return nil
+	}
+	return e.EncodeElement(tDate.Format(time.RFC3339), startElement)
+}
+
+// TransitionDays is a type alias to unmarshal Days in Transition
+type TransitionDays int
+
+// UnmarshalXML parses number of days from Transition and validates if
+// >= 0
+func (tDays *TransitionDays) UnmarshalXML(d *xml.Decoder, startElement xml.StartElement) error {
+	var numDays int
+	err := d.DecodeElement(&numDays, &startElement)
+	if err != nil {
+		return err
+	}
+	if numDays < 0 {
+		return errTransitionInvalidDays
+	}
+	*tDays = TransitionDays(numDays)
+	return nil
+}
+
+// MarshalXML encodes number of days to expire if it is non-zero and
+// encodes empty string otherwise
+func (tDays TransitionDays) MarshalXML(e *xml.Encoder, startElement xml.StartElement) error {
+	if tDays == 0 {
+		return nil
+	}
+	return e.EncodeElement(int(tDays), startElement)
+}
+
 // Transition - transition actions for a rule in lifecycle configuration.
 type Transition struct {
-	XMLName      xml.Name `xml:"Transition"`
-	Days         int      `xml:"Days,omitempty"`
-	Date         string   `xml:"Date,omitempty"`
-	StorageClass string   `xml:"StorageClass"`
+	XMLName      xml.Name       `xml:"Transition"`
+	Days         TransitionDays `xml:"Days,omitempty"`
+	Date         TransitionDate `xml:"Date,omitempty"`
+	StorageClass string         `xml:"StorageClass,omitempty"`
+
+	set bool
 }
 
-var errTransitionUnsupported = Errorf("Specifying <Transition></Transition> tag is not supported")
-
-// UnmarshalXML is extended to indicate lack of support for Transition
-// xml tag in object lifecycle configuration
-func (t Transition) UnmarshalXML(d *xml.Decoder, start xml.StartElement) error {
-	return errTransitionUnsupported
+// MarshalXML encodes transition field into an XML form.
+func (t Transition) MarshalXML(enc *xml.Encoder, start xml.StartElement) error {
+	if !t.set {
+		return nil
+	}
+	type transitionWrapper Transition
+	return enc.EncodeElement(transitionWrapper(t), start)
 }
 
-// MarshalXML is extended to leave out <Transition></Transition> tags
-func (t Transition) MarshalXML(e *xml.Encoder, start xml.StartElement) error {
+// UnmarshalXML decodes transition field from the XML form.
+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 "Expiration" element
+func (t Transition) Validate() error {
+	if !t.set {
+		return nil
+	}
+
+	if t.IsDaysNull() && t.IsDateNull() {
+		return errXMLNotWellFormed
+	}
+
+	// Both transition days and date are specified
+	if !t.IsDaysNull() && !t.IsDateNull() {
+		return errTransitionInvalid
+	}
+	if t.StorageClass == "" {
+		return errXMLNotWellFormed
+	}
+	return nil
+}
+
+// IsDaysNull returns true if days field is null
+func (t Transition) IsDaysNull() bool {
+	return t.Days == TransitionDays(0)
+}
+
+// IsDateNull returns true if date field is null
+func (t Transition) IsDateNull() bool {
+	return t.Date.Time.IsZero()
+}
+
+// IsNull returns true if both date and days fields are null
+func (t Transition) IsNull() bool {
+	return t.IsDaysNull() && t.IsDateNull()
+}