api: fix panic when region doesn't have a leader (tikv#7629)

close tikv#7630

Signed-off-by: Ryan Leung <[email protected]>

Co-authored-by: ti-chi-bot[bot] <108142056+ti-chi-bot[bot]@users.noreply.github.com>

server/api/region.go

@@ -256,7 +256,13 @@ func (h *regionHandler) GetRegionByID(w http.ResponseWriter, r *http.Request) {
 	}
 
 	regionInfo := rc.GetRegion(regionID)
-	h.rd.JSON(w, http.StatusOK, NewAPIRegionInfo(regionInfo))
+	b, err := marshalRegionInfoJSON(r.Context(), regionInfo)
+	if err != nil {
+		h.rd.JSON(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	h.rd.Data(w, http.StatusOK, b)
 }
 
 // @Tags     region
@@ -286,7 +292,13 @@ func (h *regionHandler) GetRegion(w http.ResponseWriter, r *http.Request) {
 	}
 
 	regionInfo := rc.GetRegionByKey([]byte(key))
-	h.rd.JSON(w, http.StatusOK, NewAPIRegionInfo(regionInfo))
+	b, err := marshalRegionInfoJSON(r.Context(), regionInfo)
+	if err != nil {
+		h.rd.JSON(w, http.StatusInternalServerError, err.Error())
+		return
+	}
+
+	h.rd.Data(w, http.StatusOK, b)
 }
 
 // @Tags     region
@@ -323,6 +335,24 @@ func newRegionsHandler(svr *server.Server, rd *render.Render) *regionsHandler {
 	}
 }
 
+// marshalRegionInfoJSON marshals region to bytes in `RegionInfo`'s JSON format.
+// It is used to reduce the cost of JSON serialization.
+func marshalRegionInfoJSON(ctx context.Context, r *core.RegionInfo) ([]byte, error) {
+	out := &jwriter.Writer{}
+
+	region := &RegionInfo{}
+	select {
+	case <-ctx.Done():
+		// Return early, avoid the unnecessary computation.
+		// See more details in https://github.com/tikv/pd/issues/6835
+		return nil, ctx.Err()
+	default:
+	}
+
+	covertAPIRegionInfo(r, region, out)
+	return out.Buffer.BuildBytes(), out.Error
+}
+
 // marshalRegionsInfoJSON marshals regions to bytes in `RegionsInfo`'s JSON format.
 // It is used to reduce the cost of JSON serialization.
 func marshalRegionsInfoJSON(ctx context.Context, regions []*core.RegionInfo) ([]byte, error) {
@@ -346,27 +376,31 @@ func marshalRegionsInfoJSON(ctx context.Context, regions []*core.RegionInfo) ([]
 		if i > 0 {
 			out.RawByte(',')
 		}
-		InitRegion(r, region)
-		// EasyJSON will not check anonymous struct pointer field and will panic if the field is nil.
-		// So we need to set the field to default value explicitly when the anonymous struct pointer is nil.
-		region.Leader.setDefaultIfNil()
-		for i := range region.Peers {
-			region.Peers[i].setDefaultIfNil()
-		}
-		for i := range region.PendingPeers {
-			region.PendingPeers[i].setDefaultIfNil()
-		}
-		for i := range region.DownPeers {
-			region.DownPeers[i].setDefaultIfNil()
-		}
-		region.MarshalEasyJSON(out)
+		covertAPIRegionInfo(r, region, out)
 	}
 	out.RawByte(']')
 
 	out.RawByte('}')
 	return out.Buffer.BuildBytes(), out.Error
 }
 
+func covertAPIRegionInfo(r *core.RegionInfo, region *RegionInfo, out *jwriter.Writer) {
+	InitRegion(r, region)
+	// EasyJSON will not check anonymous struct pointer field and will panic if the field is nil.
+	// So we need to set the field to default value explicitly when the anonymous struct pointer is nil.
+	region.Leader.setDefaultIfNil()
+	for i := range region.Peers {
+		region.Peers[i].setDefaultIfNil()
+	}
+	for i := range region.PendingPeers {
+		region.PendingPeers[i].setDefaultIfNil()
+	}
+	for i := range region.DownPeers {
+		region.DownPeers[i].setDefaultIfNil()
+	}
+	region.MarshalEasyJSON(out)
+}
+
 // @Tags     region
 // @Summary  List all regions in the cluster.
 // @Produce  json

tools/pd-ctl/tests/region/region_test.go

@@ -208,3 +208,56 @@ func TestRegion(t *testing.T) {
 		{core.HexRegionKeyStr(r5.GetEndKey()), ""},
 	}, *rangeHoles)
 }
+
+func TestRegionNoLeader(t *testing.T) {
+	re := require.New(t)
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+	cluster, err := pdTests.NewTestCluster(ctx, 1)
+	re.NoError(err)
+	err = cluster.RunInitialServers()
+	re.NoError(err)
+	cluster.WaitLeader()
+	url := cluster.GetConfig().GetClientURL()
+	stores := []*metapb.Store{
+		{
+			Id:            1,
+			State:         metapb.StoreState_Up,
+			LastHeartbeat: time.Now().UnixNano(),
+		},
+		{
+			Id:            2,
+			State:         metapb.StoreState_Up,
+			LastHeartbeat: time.Now().UnixNano(),
+		},
+		{
+			Id:            3,
+			State:         metapb.StoreState_Up,
+			LastHeartbeat: time.Now().UnixNano(),
+		},
+	}
+
+	leaderServer := cluster.GetLeaderServer()
+	re.NoError(leaderServer.BootstrapCluster())
+	for i := 0; i < len(stores); i++ {
+		pdTests.MustPutStore(re, cluster, stores[i])
+	}
+
+	metaRegion := &metapb.Region{
+		Id:       100,
+		StartKey: []byte(""),
+		EndKey:   []byte(""),
+		Peers: []*metapb.Peer{
+			{Id: 1, StoreId: 1},
+			{Id: 5, StoreId: 2},
+			{Id: 6, StoreId: 3}},
+		RegionEpoch: &metapb.RegionEpoch{ConfVer: 1, Version: 1},
+	}
+	r := core.NewRegionInfo(metaRegion, nil)
+
+	cluster.GetLeaderServer().GetRaftCluster().GetBasicCluster().SetRegion(r)
+
+	cmd := ctl.GetRootCmd()
+	_, err = tests.ExecuteCommand(cmd, "-u", url, "region", "100")
+	re.NoError(err)
+}