api: support to query whether pd has loaded region

pkg/storage/storage.go

@@ -77,9 +77,10 @@ type coreStorage struct {
 	Storage
 	regionStorage endpoint.RegionStorage
 
-	useRegionStorage int32
-	regionLoaded     bool
-	mu               syncutil.Mutex
+	useRegionStorage        int32
+	regionLoadedFromDefault bool
+	regionLoadedFromStorage bool
+	mu                      syncutil.RWMutex
 }
 
 // NewCoreStorage creates a new core storage with the given default and region storage.
@@ -133,17 +134,22 @@ func TryLoadRegionsOnce(ctx context.Context, s Storage, f func(region *core.Regi
 		return s.LoadRegions(ctx, f)
 	}
 
+	ps.mu.Lock()
+	defer ps.mu.Unlock()
+
 	if atomic.LoadInt32(&ps.useRegionStorage) == 0 {
-		return ps.Storage.LoadRegions(ctx, f)
+		err := ps.Storage.LoadRegions(ctx, f)
+		if err == nil {
+			ps.regionLoadedFromDefault = true
+		}
+		return err
 	}
 
-	ps.mu.Lock()
-	defer ps.mu.Unlock()
-	if !ps.regionLoaded {
+	if !ps.regionLoadedFromStorage {
 		if err := ps.regionStorage.LoadRegions(ctx, f); err != nil {
 			return err
 		}
-		ps.regionLoaded = true
+		ps.regionLoadedFromStorage = true
 	}
 	return nil
 }
@@ -197,3 +203,14 @@ func (ps *coreStorage) Close() error {
 	}
 	return nil
 }
+
+// AreRegionsLoaded returns whether the regions are loaded.
+func AreRegionsLoaded(s Storage) bool {
+	ps := s.(*coreStorage)
+	ps.mu.RLock()
+	defer ps.mu.RUnlock()
+	if atomic.LoadInt32(&ps.useRegionStorage) == 0 {
+		return ps.regionLoadedFromDefault
+	}
+	return ps.regionLoadedFromStorage
+}

pkg/versioninfo/versioninfo.go

@@ -31,6 +31,7 @@ type Status struct {
 	Version        string `json:"version"`
 	GitHash        string `json:"git_hash"`
 	StartTimestamp int64  `json:"start_timestamp"`
+	Loaded         bool   `json:"loaded"`
 }
 
 const (

server/api/status.go

@@ -17,6 +17,7 @@ package api
 import (
 	"net/http"
 
+	"github.com/tikv/pd/pkg/storage"
 	"github.com/tikv/pd/pkg/versioninfo"
 	"github.com/tikv/pd/server"
 	"github.com/unrolled/render"
@@ -44,6 +45,7 @@ func (h *statusHandler) GetPDStatus(w http.ResponseWriter, _ *http.Request) {
 		GitHash:        versioninfo.PDGitHash,
 		Version:        versioninfo.PDReleaseVersion,
 		StartTimestamp: h.svr.StartTimestamp(),
+		Loaded:         storage.AreRegionsLoaded(h.svr.GetStorage()),
 	}
 
 	h.rd.JSON(w, http.StatusOK, version)