Merge pull request #1099 from unihorn/128

wal: OpenFromIndex fails if it cannot find previous index

wal/wal.go

@@ -42,10 +42,11 @@ const (
 )
 
 var (
-	ErrIDMismatch  = errors.New("wal: unmatch id")
-	ErrNotFound    = errors.New("wal: file is not found")
-	ErrCRCMismatch = errors.New("wal: crc mismatch")
-	crcTable       = crc32.MakeTable(crc32.Castagnoli)
+	ErrIDMismatch    = errors.New("wal: unmatch id")
+	ErrFileNotFound  = errors.New("wal: file not found")
+	ErrIndexNotFound = errors.New("wal: index not found in file")
+	ErrCRCMismatch   = errors.New("wal: crc mismatch")
+	crcTable         = crc32.MakeTable(crc32.Castagnoli)
 )
 
 // WAL is a logical repersentation of the stable storage.
@@ -94,7 +95,8 @@ func Create(dirpath string) (*WAL, error) {
 }
 
 // OpenAtIndex opens the WAL at the given index.
-// The index MUST have been previously committed to the WAL.
+// The index SHOULD have been previously committed to the WAL, or the following
+// ReadAll will fail.
 // The returned WAL is ready to read and the first record will be the given
 // index. The WAL cannot be appended to before reading out all of its
 // previous records.
@@ -106,14 +108,14 @@ func OpenAtIndex(dirpath string, index int64) (*WAL, error) {
 	}
 	names = checkWalNames(names)
 	if len(names) == 0 {
-		return nil, ErrNotFound
+		return nil, ErrFileNotFound
 	}
 
 	sort.Sort(sort.StringSlice(names))
 
 	nameIndex, ok := searchIndex(names, index)
 	if !ok || !isValidSeq(names[nameIndex:]) {
-		return nil, ErrNotFound
+		return nil, ErrFileNotFound
 	}
 
 	// open the wal files for reading
@@ -153,6 +155,7 @@ func OpenAtIndex(dirpath string, index int64) (*WAL, error) {
 }
 
 // ReadAll reads out all records of the current WAL.
+// If it cannot read out the expected entry, it will return ErrIndexNotFound.
 // After ReadAll, the WAL will be ready for appending new records.
 func (w *WAL) ReadAll() (id int64, state raftpb.HardState, ents []raftpb.Entry, err error) {
 	rec := &walpb.Record{}
@@ -193,6 +196,10 @@ func (w *WAL) ReadAll() (id int64, state raftpb.HardState, ents []raftpb.Entry,
 		state.Reset()
 		return 0, state, nil, err
 	}
+	if w.enti < w.ri {
+		state.Reset()
+		return 0, state, nil, ErrIndexNotFound
+	}
 
 	// close decoder, disable reading
 	w.decoder.close()

wal/wal_test.go

@@ -111,8 +111,8 @@ func TestOpenAtIndex(t *testing.T) {
 		t.Fatal(err)
 	}
 	defer os.RemoveAll(emptydir)
-	if _, err = OpenAtIndex(emptydir, 0); err != ErrNotFound {
-		t.Errorf("err = %v, want %v", err, ErrNotFound)
+	if _, err = OpenAtIndex(emptydir, 0); err != ErrFileNotFound {
+		t.Errorf("err = %v, want %v", err, ErrFileNotFound)
 	}
 }
 
@@ -315,8 +315,8 @@ func TestRecoverAfterCut(t *testing.T) {
 		w, err := OpenAtIndex(p, int64(i))
 		if err != nil {
 			if i <= 4 {
-				if err != ErrNotFound {
-					t.Errorf("#%d: err = %v, want %v", i, err, ErrNotFound)
+				if err != ErrFileNotFound {
+					t.Errorf("#%d: err = %v, want %v", i, err, ErrFileNotFound)
 				}
 			} else {
 				t.Errorf("#%d: err = %v, want nil", i, err)
@@ -339,6 +339,33 @@ func TestRecoverAfterCut(t *testing.T) {
 	}
 }
 
+func TestOpenAtUncommittedIndex(t *testing.T) {
+	p, err := ioutil.TempDir(os.TempDir(), "waltest")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(p)
+
+	w, err := Create(p)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := w.SaveEntry(&raftpb.Entry{Index: 0}); err != nil {
+		t.Fatal(err)
+	}
+	w.Close()
+
+	w, err = OpenAtIndex(p, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// commit up to index 0, try to read index 1
+	if _, _, _, err := w.ReadAll(); err != ErrIndexNotFound {
+		t.Errorf("err = %v, want %v", err, ErrIndexNotFound)
+	}
+	w.Close()
+}
+
 func TestSaveEmpty(t *testing.T) {
 	var buf bytes.Buffer
 	var est raftpb.HardState