Avoid double bucket validation in DeleteObjectHandler (#6720)

On a heavily loaded server, getBucketInfo() becomes slow,
one can easily observe deleting an object causes many
additional network calls.

This PR is to let the underlying call return the actual
error and write it back to the client.

cmd/object-handlers.go

@@ -2091,21 +2091,18 @@ func (api objectAPIHandlers) DeleteObjectHandler(w http.ResponseWriter, r *http.
 			}
 			return
 		}
-	} else {
-		getBucketInfo := objectAPI.GetBucketInfo
-		if api.CacheAPI() != nil {
-			getBucketInfo = api.CacheAPI().GetBucketInfo
 	}
-		if _, err := getBucketInfo(ctx, bucket); err != nil {
-			writeErrorResponse(w, toAPIErrorCode(err), r.URL)
+
+	// http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectDELETE.html
+	if err := deleteObject(ctx, objectAPI, api.CacheAPI(), bucket, object, r); err != nil {
+		switch toAPIErrorCode(err) {
+		case ErrNoSuchBucket:
+			// When bucket doesn't exist specially handle it.
+			writeErrorResponse(w, ErrNoSuchBucket, r.URL)
 			return
 		}
+		logger.LogIf(ctx, err)
+		// Ignore delete object errors while replying to client, since we are suppposed to reply only 204.
 	}
-
-	// http://docs.aws.amazon.com/AmazonS3/latest/API/RESTObjectDELETE.html
-	// Ignore delete object errors while replying to client, since we are
-	// suppposed to reply only 204. Additionally log the error for
-	// investigation.
-	deleteObject(ctx, objectAPI, api.CacheAPI(), bucket, object, r)
 	writeSuccessNoContent(w)
 }

cmd/xl-v1-object.go

@@ -984,13 +984,13 @@ func (xl xlObjects) DeleteObject(ctx context.Context, bucket, object string) (er
 		return err
 	}
 
-	if !xl.isObject(bucket, object) && !xl.isObjectDir(bucket, object) {
-		return ObjectNotFound{bucket, object}
-	}
-
 	var writeQuorum int
 	var isObjectDir = hasSuffix(object, slashSeparator)
 
+	if isObjectDir && !xl.isObjectDir(bucket, object) {
+		return toObjectErr(errFileNotFound, bucket, object)
+	}
+
 	if isObjectDir {
 		writeQuorum = len(xl.getDisks())/2 + 1
 	} else {

cmd/xl-v1-utils.go

@@ -305,7 +305,7 @@ func readXLMeta(ctx context.Context, disk StorageAPI, bucket string, object stri
 	// Reads entire `xl.json`.
 	xlMetaBuf, err := disk.ReadAll(bucket, path.Join(object, xlMetaJSONFile))
 	if err != nil {
-		if err != errFileNotFound {
+		if err != errFileNotFound && err != errVolumeNotFound {
 			logger.GetReqInfo(ctx).AppendTags("disk", disk.String())
 			logger.LogIf(ctx, err)
 		}