treat 0-byte objects to honor same quorum as delete marker (#17633)

on unversioned buckets its possible that 0-byte objects
might lose quorum on flaky systems, allow them to be same
as DELETE markers. Since practically speak they have no
content.

cmd/erasure-metadata.go

@@ -350,8 +350,11 @@ func findFileInfoInQuorum(ctx context.Context, metaArr []FileInfo, modTime time.
 			for _, part := range meta.Parts {
 				fmt.Fprintf(h, "part.%d", part.Number)
 			}
-			fmt.Fprintf(h, "%v+%v", meta.Erasure.DataBlocks, meta.Erasure.ParityBlocks)
-			fmt.Fprintf(h, "%v", meta.Erasure.Distribution)
+
+			if !meta.Deleted && meta.Size != 0 {
+				fmt.Fprintf(h, "%v+%v", meta.Erasure.DataBlocks, meta.Erasure.ParityBlocks)
+				fmt.Fprintf(h, "%v", meta.Erasure.Distribution)
+			}
 
 			// ILM transition fields
 			fmt.Fprint(h, meta.TransitionStatus)
@@ -499,7 +502,8 @@ func listObjectParities(partsMetadata []FileInfo, errs []error) (parities []int)
 			parities[index] = -1
 			continue
 		}
-		if metadata.Deleted {
+		// Delete marker or zero byte objects take highest parity.
+		if metadata.Deleted || metadata.Size == 0 {
 			parities[index] = len(partsMetadata) / 2
 		} else {
 			parities[index] = metadata.Erasure.ParityBlocks

cmd/erasure-object.go

@@ -278,6 +278,11 @@ func (er erasureObjects) GetObjectNInfo(ctx context.Context, bucket, object stri
 		return gr.WithCleanupFuncs(nsUnlocker), nil
 	}
 
+	if objInfo.Size == 0 {
+		// Zero byte objects don't even need to further initialize pipes etc.
+		return NewGetObjectReaderFromReader(bytes.NewReader(nil), objInfo, opts)
+	}
+
 	fn, off, length, err := NewGetObjectReader(rs, objInfo, opts)
 	if err != nil {
 		return nil, err