18376: Complete series of readdirent calls as quickly as possible.

Arvados-DCO-1.1-Signed-off-by: Tom Clegg <tom@curii.com>

diff --git a/services/keepstore/unix_volume.go b/services/keepstore/unix_volume.go
index f076ccf18419675499e12eed0e3d017824af8e57..46f4db4095bfb286c82f4f07a988c16cee5ebe63 100644 (file)
--- a/services/keepstore/unix_volume.go
+++ b/services/keepstore/unix_volume.go
@@ -359,47 +359,53 @@ var blockFileRe = regexp.MustCompile(`^[0-9a-f]{32}$`)
 //     e4de7a2810f5554cd39b36d8ddb132ff+67108864 1388701136
 //
 func (v *UnixVolume) IndexTo(prefix string, w io.Writer) error {
-       var lastErr error
        rootdir, err := v.os.Open(v.Root)
        if err != nil {
                return err
        }
-       defer rootdir.Close()
        v.os.stats.TickOps("readdir")
        v.os.stats.Tick(&v.os.stats.ReaddirOps)
-       for {
-               names, err := rootdir.Readdirnames(1)
-               if err == io.EOF {
-                       return lastErr
-               } else if err != nil {
-                       return err
-               }
-               if !strings.HasPrefix(names[0], prefix) && !strings.HasPrefix(prefix, names[0]) {
+       subdirs, err := rootdir.Readdirnames(-1)
+       rootdir.Close()
+       if err != nil {
+               return err
+       }
+       for _, subdir := range subdirs {
+               if !strings.HasPrefix(subdir, prefix) && !strings.HasPrefix(prefix, subdir) {
                        // prefix excludes all blocks stored in this dir
                        continue
                }
-               if !blockDirRe.MatchString(names[0]) {
+               if !blockDirRe.MatchString(subdir) {
                        continue
                }
-               blockdirpath := filepath.Join(v.Root, names[0])
+               blockdirpath := filepath.Join(v.Root, subdir)
                blockdir, err := v.os.Open(blockdirpath)
                if err != nil {
                        v.logger.WithError(err).Errorf("error reading %q", blockdirpath)
-                       lastErr = fmt.Errorf("error reading %q: %s", blockdirpath, err)
-                       continue
+                       return fmt.Errorf("error reading %q: %s", blockdirpath, err)
                }
                v.os.stats.TickOps("readdir")
                v.os.stats.Tick(&v.os.stats.ReaddirOps)
-               for {
-                       fileInfo, err := blockdir.Readdir(1)
-                       if err == io.EOF {
-                               break
+               // ReadDir() (compared to Readdir(), which returns
+               // FileInfo structs) helps complete the sequence of
+               // readdirent calls as quickly as possible, reducing
+               // the likelihood of NFS EBADCOOKIE (523) errors.
+               dirents, err := blockdir.ReadDir(-1)
+               blockdir.Close()
+               if err != nil {
+                       v.logger.WithError(err).Errorf("error reading %q", blockdirpath)
+                       return fmt.Errorf("error reading %q: %s", blockdirpath, err)
+               }
+               for _, dirent := range dirents {
+                       fileInfo, err := dirent.Info()
+                       if os.IsNotExist(err) {
+                               // File disappeared between ReadDir() and now
+                               continue
                        } else if err != nil {
-                               v.logger.WithError(err).Errorf("error reading %q", blockdirpath)
-                               lastErr = fmt.Errorf("error reading %q: %s", blockdirpath, err)
-                               break
+                               v.logger.WithError(err).Errorf("error getting FileInfo for %q in %q", dirent.Name(), blockdirpath)
+                               return err
                        }
-                       name := fileInfo[0].Name()
+                       name := fileInfo.Name()
                        if !strings.HasPrefix(name, prefix) {
                                continue
                        }
@@ -408,16 +414,15 @@ func (v *UnixVolume) IndexTo(prefix string, w io.Writer) error {
                        }
                        _, err = fmt.Fprint(w,
                                name,
-                               "+", fileInfo[0].Size(),
-                               " ", fileInfo[0].ModTime().UnixNano(),
+                               "+", fileInfo.Size(),
+                               " ", fileInfo.ModTime().UnixNano(),
                                "\n")
                        if err != nil {
-                               blockdir.Close()
                                return fmt.Errorf("error writing: %s", err)
                        }
                }
-               blockdir.Close()
        }
+       return nil
 }
 
 // Trash trashes the block data from the unix storage