Add x-amz-expiration header in some S3 responses (#9667)

x-amz-expiration is described in the S3 specification as a header which
indicates if the object in question will expire any time in the future.

pkg/bucket/lifecycle/lifecycle.go

@@ -95,9 +95,9 @@ func (lc Lifecycle) Validate() error {
 
 // FilterRuleActions returns the expiration and transition from the object name
 // after evaluating all rules.
-func (lc Lifecycle) FilterRuleActions(objName, objTags string) (Expiration, Transition) {
+func (lc Lifecycle) FilterRuleActions(objName, objTags string) (string, Expiration, Transition) {
 	if objName == "" {
-		return Expiration{}, Transition{}
+		return "", Expiration{}, Transition{}
 	}
 	for _, rule := range lc.Rules {
 		if rule.Status == Disabled {
@@ -107,14 +107,14 @@ func (lc Lifecycle) FilterRuleActions(objName, objTags string) (Expiration, Tran
 		if strings.HasPrefix(objName, rule.Prefix()) {
 			if tags != "" {
 				if strings.Contains(objTags, tags) {
-					return rule.Expiration, Transition{}
+					return rule.ID, rule.Expiration, Transition{}
 				}
 			} else {
-				return rule.Expiration, Transition{}
+				return rule.ID, rule.Expiration, Transition{}
 			}
 		}
 	}
-	return Expiration{}, Transition{}
+	return "", Expiration{}, Transition{}
 }
 
 // ComputeAction returns the action to perform by evaluating all lifecycle rules
@@ -124,16 +124,38 @@ func (lc Lifecycle) ComputeAction(objName, objTags string, modTime time.Time) Ac
 	if modTime.IsZero() {
 		return action
 	}
-	exp, _ := lc.FilterRuleActions(objName, objTags)
+	_, exp, _ := lc.FilterRuleActions(objName, objTags)
 	if !exp.IsDateNull() {
 		if time.Now().After(exp.Date.Time) {
 			action = DeleteAction
 		}
 	}
 	if !exp.IsDaysNull() {
-		if time.Now().After(modTime.Add(time.Duration(exp.Days) * 24 * time.Hour)) {
+		if time.Now().After(expectedExpiryTime(modTime, exp.Days)) {
 			action = DeleteAction
 		}
 	}
 	return action
 }
+
+// expectedExpiryTime calculates the expiry date/time based on a object modtime.
+// The expected expiry time is always a midnight time following the the object
+// modification time plus the number of expiration days.
+//   e.g. If the object modtime is `Thu May 21 13:42:50 GMT 2020` and the object should
+//        expire in 1 day, then the expected expiry time is `Fri, 23 May 2020 00:00:00 GMT`
+func expectedExpiryTime(modTime time.Time, days ExpirationDays) time.Time {
+	t := modTime.UTC().Add(time.Duration(days+1) * 24 * time.Hour)
+	return t.Truncate(24 * time.Hour)
+}
+
+// PredictExpiryTime returns the expiry date/time of a given object
+func (lc Lifecycle) PredictExpiryTime(objName, objTags string) (string, time.Time) {
+	ruleID, exp, _ := lc.FilterRuleActions(objName, objTags)
+	if !exp.IsDateNull() {
+		return ruleID, exp.Date.Time
+	}
+	if !exp.IsDaysNull() {
+		return ruleID, expectedExpiryTime(time.Now(), exp.Days)
+	}
+	return "", time.Time{}
+}

pkg/bucket/lifecycle/lifecycle_test.go

@@ -168,6 +168,35 @@ func TestMarshalLifecycleConfig(t *testing.T) {
 	}
 }
 
+func TestExpectedExpiryTime(t *testing.T) {
+	testCases := []struct {
+		modTime  time.Time
+		days     ExpirationDays
+		expected time.Time
+	}{
+		{
+			time.Date(2020, time.March, 15, 10, 10, 10, 0, time.UTC),
+			4,
+			time.Date(2020, time.March, 20, 0, 0, 0, 0, time.UTC),
+		},
+		{
+			time.Date(2020, time.March, 15, 0, 0, 0, 0, time.UTC),
+			1,
+			time.Date(2020, time.March, 17, 0, 0, 0, 0, time.UTC),
+		},
+	}
+
+	for i, tc := range testCases {
+		t.Run(fmt.Sprintf("Test %d", i+1), func(t *testing.T) {
+			got := expectedExpiryTime(tc.modTime, tc.days)
+			if got != tc.expected {
+				t.Fatalf("Expected %v to be equal to %v", got, tc.expected)
+			}
+		})
+	}
+
+}
+
 func TestComputeActions(t *testing.T) {
 	testCases := []struct {
 		inputConfig    string