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.

cmd/object-handlers-common.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"regexp"
 	"time"
@@ -252,6 +253,19 @@ func isETagEqual(left, right string) bool {
 	return canonicalizeETag(left) == canonicalizeETag(right)
 }
 
+// setAmzExpirationHeader sets x-amz-expiration header with expiry time
+// after analyzing the current bucket lifecycle rules if any.
+func setAmzExpirationHeader(w http.ResponseWriter, bucket string, objInfo ObjectInfo) {
+	if lc, err := globalLifecycleSys.Get(bucket); err == nil {
+		ruleID, expiryTime := lc.PredictExpiryTime(objInfo.Name, objInfo.UserTags)
+		if !expiryTime.IsZero() {
+			w.Header()[xhttp.AmzExpiration] = []string{
+				fmt.Sprintf(`expiry-date="%s", rule-id="%s"`, expiryTime.Format(http.TimeFormat), ruleID),
+			}
+		}
+	}
+}
+
 // deleteObject is a convenient wrapper to delete an object, this
 // is a common function to be called from object handlers and
 // web handlers.