Store can handle snapshotting empty WAL files

snapshot/snapshot_test.go

@@ -0,0 +1,72 @@
+package snapshot
+
+import (
+	"bytes"
+	"io"
+	"testing"
+)
+
+func Test_SnapshotNew(t *testing.T) {
+	// Create a new snapshot
+	s := NewSnapshot(nil)
+	if s == nil {
+		t.Errorf("expected snapshot to be created")
+	}
+}
+
+// Test_SnapshotPersist_NilData tests that Persist does not error when
+// given a nil data buffer.
+func Test_SnapshotPersist_NilData(t *testing.T) {
+	compactedBuf := bytes.NewBuffer(nil)
+	s := NewSnapshot(io.NopCloser(compactedBuf))
+	if s == nil {
+		t.Errorf("expected snapshot to be created")
+	}
+
+	mrs := &mockRaftSink{}
+	err := s.Persist(mrs)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+	}
+	if len(mrs.buf.Bytes()) != 0 {
+		t.Errorf("expected %d, got %d", 0, len(mrs.buf.Bytes()))
+	}
+}
+
+func Test_SnapshotPersist_SimpleData(t *testing.T) {
+	compactedBuf := bytes.NewBuffer([]byte("hello world"))
+	s := NewSnapshot(io.NopCloser(compactedBuf))
+	if s == nil {
+		t.Errorf("expected snapshot to be created")
+	}
+
+	mrs := &mockRaftSink{}
+	err := s.Persist(mrs)
+	if err != nil {
+		t.Errorf("expected no error, got %v", err)
+	}
+	if mrs.buf.String() != "hello world" {
+		t.Errorf("expected %s, got %s", "hello world", mrs.buf.String())
+	}
+}
+
+type mockRaftSink struct {
+	buf bytes.Buffer
+}
+
+func (mrs *mockRaftSink) Write(p []byte) (n int, err error) {
+	return mrs.buf.Write(p)
+}
+
+func (mrs *mockRaftSink) Close() error {
+	return nil
+}
+
+// implement cancel
+func (mrs *mockRaftSink) Cancel() error {
+	return nil
+}
+
+func (mrs *mockRaftSink) ID() string {
+	return ""
+}

store/store.go

@@ -1780,7 +1780,7 @@ func (s *Store) Snapshot() (raft.FSMSnapshot, error) {
 	} else {
 		compactedBuf := bytes.NewBuffer(nil)
 		var err error
-		if pathExists(s.db.WALPath()) {
+		if pathExistsWithData(s.db.WALPath()) {
 			walFD, err := os.Open(s.db.WALPath())
 			if err != nil {
 				return nil, err
@@ -2390,6 +2390,17 @@ func pathExists(p string) bool {
 	return true
 }
 
+// pathExistsWithData returns true if the given path exists and has data.
+func pathExistsWithData(p string) bool {
+	if !pathExists(p) {
+		return false
+	}
+	if size, err := fileSize(p); err != nil || size == 0 {
+		return false
+	}
+	return true
+}
+
 func dirExists(path string) bool {
 	stat, err := os.Stat(path)
 	return err == nil && stat.IsDir()