add more debug info for opening WAL files failure

Signed-off-by: Benjamin Wang <wachao@vmware.com>

server/storage/wal/util.go

@@ -72,7 +72,7 @@ func isValidSeq(lg *zap.Logger, names []string) bool {
 func readWALNames(lg *zap.Logger, dirpath string) ([]string, error) {
 	names, err := fileutil.ReadDir(dirpath)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("[readWALNames] fileutil.ReadDir failed: %w", err)
 	}
 	wnames := checkWalNames(lg, names)
 	if len(wnames) == 0 {

server/storage/wal/wal.go

@@ -318,10 +318,10 @@ func (w *WAL) renameWALUnlock(tmpdirpath string) (*WAL, error) {
 func Open(lg *zap.Logger, dirpath string, snap walpb.Snapshot) (*WAL, error) {
 	w, err := openAtIndex(lg, dirpath, snap, true)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("openAtIndex failed: %w", err)
 	}
 	if w.dirFile, err = fileutil.OpenDir(w.dir); err != nil {
-		return nil, err
+		return nil, fmt.Errorf("fileutil.OpenDir failed: %w", err)
 	}
 	return w, nil
 }
@@ -338,12 +338,12 @@ func openAtIndex(lg *zap.Logger, dirpath string, snap walpb.Snapshot, write bool
 	}
 	names, nameIndex, err := selectWALFiles(lg, dirpath, snap)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("[openAtIndex] selectWALFiles failed: %w", err)
 	}
 
 	rs, ls, closer, err := openWALFiles(lg, dirpath, names, nameIndex, write)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("[openAtIndex] openWALFiles failed: %w", err)
 	}
 
 	// create a WAL ready for reading
@@ -362,7 +362,7 @@ func openAtIndex(lg *zap.Logger, dirpath string, snap walpb.Snapshot, write bool
 		w.readClose = nil
 		if _, _, err := parseWALName(filepath.Base(w.tail().Name())); err != nil {
 			closer()
-			return nil, err
+			return nil, fmt.Errorf("[openAtIndex] parseWALName failed: %w", err)
 		}
 		w.fp = newFilePipeline(lg, w.dir, SegmentSizeBytes)
 	}
@@ -373,7 +373,7 @@ func openAtIndex(lg *zap.Logger, dirpath string, snap walpb.Snapshot, write bool
 func selectWALFiles(lg *zap.Logger, dirpath string, snap walpb.Snapshot) ([]string, int, error) {
 	names, err := readWALNames(lg, dirpath)
 	if err != nil {
-		return nil, -1, err
+		return nil, -1, fmt.Errorf("readWALNames failed: %w", err)
 	}
 
 	nameIndex, ok := searchIndex(lg, names, snap.Index)
@@ -399,7 +399,7 @@ func openWALFiles(lg *zap.Logger, dirpath string, names []string, nameIndex int,
 			l, err := fileutil.TryLockFile(p, os.O_RDWR, fileutil.PrivateFileMode)
 			if err != nil {
 				closeAll(lg, rcs...)
-				return nil, nil, nil, err
+				return nil, nil, nil, fmt.Errorf("[openWALFiles] fileutil.TryLockFile failed: %w", err)
 			}
 			ls = append(ls, l)
 			rcs = append(rcs, l)
@@ -408,7 +408,7 @@ func openWALFiles(lg *zap.Logger, dirpath string, names []string, nameIndex int,
 			rf, err := os.OpenFile(p, os.O_RDONLY, fileutil.PrivateFileMode)
 			if err != nil {
 				closeAll(lg, rcs...)
-				return nil, nil, nil, err
+				return nil, nil, nil, fmt.Errorf("[openWALFiles] os.OpenFile failed (%q): %w", p, err)
 			}
 			ls = append(ls, nil)
 			rcs = append(rcs, rf)

server/storage/wal/wal_test.go

@@ -16,6 +16,7 @@ package wal
 
 import (
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"math"
@@ -195,7 +196,7 @@ func TestOpenAtIndex(t *testing.T) {
 	w.Close()
 
 	emptydir := t.TempDir()
-	if _, err = Open(zaptest.NewLogger(t), emptydir, walpb.Snapshot{}); err != ErrFileNotFound {
+	if _, err = Open(zaptest.NewLogger(t), emptydir, walpb.Snapshot{}); !errors.Is(err, ErrFileNotFound) {
 		t.Errorf("err = %v, want %v", err, ErrFileNotFound)
 	}
 }