feat(admin): check cluster id in mrmanager

This PR adds codes to check cluster id in mrmanager. Because the admin server doesn't have explicit
health checking, comparing cluster id is performed in ClusterMetadataViewer.
In the next PR, checking the replication factor will be added.

internal/admin/mrmanager/manager.go

@@ -11,6 +11,7 @@ import (
 	"time"
 
 	"github.com/pkg/errors"
+	"golang.org/x/sync/errgroup"
 	"golang.org/x/sync/singleflight"
 
 	"github.com/kakao/varlog/pkg/mrc"
@@ -126,6 +127,7 @@ func New(ctx context.Context, opts ...Option) (MetadataRepositoryManager, error)
 			continue
 		}
 		return &mrManager{
+			config:    cfg,
 			dirty:     true,
 			connector: connector,
 		}, nil
@@ -375,11 +377,32 @@ func (mrm *mrManager) ClusterMetadata(ctx context.Context) (*varlogpb.MetadataDe
 	mrm.mu.RUnlock()
 
 	// slow path
+	return mrm.getClusterMetadataSlowly(ctx)
+}
+
+func (mrm *mrManager) getClusterMetadataSlowly(ctx context.Context) (*varlogpb.MetadataDescriptor, error) {
 	md, err, _ := mrm.sfg.Do("cluster_metadata", func() (interface{}, error) {
-		meta, err := mrm.clusterMetadata(ctx)
+		var (
+			meta *varlogpb.MetadataDescriptor
+			info *mrpb.ClusterInfo
+		)
+		eg, ctx := errgroup.WithContext(ctx)
+		eg.Go(func() (err error) {
+			meta, err = mrm.clusterMetadata(ctx)
+			return err
+		})
+		eg.Go(func() (err error) {
+			info, err = mrm.GetClusterInfo(ctx)
+			return err
+		})
+		err := eg.Wait()
 		if err != nil {
 			return nil, fmt.Errorf("cluster metadata: %w", err)
 		}
+		if info.ClusterID != mrm.cid {
+			return nil, fmt.Errorf("unexpected cluster id: expected %v, got %v", mrm.cid, info.ClusterID)
+		}
+
 		mrm.mu.Lock()
 		mrm.meta = meta
 		mrm.dirty = false