From 7710c108d9877830fcbbdfcd72acfcdba545f983 Mon Sep 17 00:00:00 2001
From: lance6716 <lance6716@gmail.com>
Date: Fri, 6 Sep 2019 16:36:00 +0800
Subject: [PATCH] manually cherry-pick for #237

---
 lightning/restore/checkpoint_test.go | 24 ++++++++++++++++++++++++
 lightning/restore/checkpoints.go     | 20 +++++++++++++++++++-
 2 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 lightning/restore/checkpoint_test.go

diff --git a/lightning/restore/checkpoint_test.go b/lightning/restore/checkpoint_test.go
new file mode 100644
index 000000000..028861312
--- /dev/null
+++ b/lightning/restore/checkpoint_test.go
@@ -0,0 +1,24 @@
+package restore
+
+import (
+	. "github.com/pingcap/check"
+	"path/filepath"
+)
+
+var _ = Suite(&checkpointSuite{})
+
+type checkpointSuite struct{}
+
+func (s *splitKVSuite) TestCheckpointMarshallUnmarshall(c *C) {
+	path := filepath.Join(c.MkDir(), "filecheckpoint")
+	fileChkp := NewFileCheckpointsDB(path)
+	fileChkp.checkpoints.Checkpoints["a"] = &TableCheckpointModel{
+		Status:  uint32(CheckpointStatusLoaded),
+		Engines: map[int32]*EngineCheckpointModel{},
+	}
+	fileChkp.Close()
+
+	fileChkp2 := NewFileCheckpointsDB(path)
+	// if not recover empty map explicitly, it will become nil
+	c.Assert(fileChkp2.checkpoints.Checkpoints["a"].Engines, NotNil)
+}
\ No newline at end of file
diff --git a/lightning/restore/checkpoints.go b/lightning/restore/checkpoints.go
index c4aadf65b..627aa3686 100644
--- a/lightning/restore/checkpoints.go
+++ b/lightning/restore/checkpoints.go
@@ -654,7 +654,25 @@ func NewFileCheckpointsDB(path string) *FileCheckpointsDB {
 	// ignore all errors -- file maybe not created yet (and it is fine).
 	content, err := ioutil.ReadFile(path)
 	if err == nil {
-		cpdb.checkpoints.Unmarshal(content)
+		err2 := cpdb.checkpoints.Unmarshal(content)
+		if err2 != nil {
+			common.AppLogger.Errorf("checkpoint file is broken %s, error: %v", path, err)
+		}
+		// FIXME: patch for empty map may need initialize manually, because currently
+		// FIXME: a map of zero size -> marshall -> unmarshall -> become nil, see checkpoint_test.go
+		if cpdb.checkpoints.Checkpoints == nil {
+			cpdb.checkpoints.Checkpoints = map[string]*TableCheckpointModel{}
+		}
+		for _, table := range cpdb.checkpoints.Checkpoints {
+			if table.Engines == nil {
+				table.Engines = map[int32]*EngineCheckpointModel{}
+			}
+			for _, engine := range table.Engines {
+				if engine.Chunks == nil {
+					engine.Chunks = map[string]*ChunkCheckpointModel{}
+				}
+			}
+		}
 	} else {
 		common.AppLogger.Warnf("failed to open checkpoint file %s, going to create a new one: %v", path, err)
 	}