fix: [2.5] improve error handling and unit tests for InitMetaCache function (#40324)

- issue: #40320
- pr: #40322

Signed-off-by: SimFG <bang.fu@zilliz.com>

internal/proxy/meta_cache.go

@@ -361,7 +361,7 @@ func InitMetaCache(ctx context.Context, rootCoord types.RootCoordClient, queryCo
 
 	// The privilege info is a little more. And to get this info, the query operation of involving multiple table queries is required.
 	resp, err := rootCoord.ListPolicy(ctx, &internalpb.ListPolicyRequest{})
-	if err != nil {
+	if err = merr.CheckRPCCall(resp, err); err != nil {
 		log.Error("fail to init meta cache", zap.Error(err))
 		return err
 	}

internal/proxy/meta_cache_test.go

@@ -385,6 +385,42 @@ func TestMetaCacheGetCollectionWithUpdate(t *testing.T) {
 	})
 }
 
+func TestMetaCache_InitCache(t *testing.T) {
+	t.Run("success", func(t *testing.T) {
+		ctx := context.Background()
+		rootCoord := mocks.NewMockRootCoordClient(t)
+		queryCoord := mocks.NewMockQueryCoordClient(t)
+		queryCoord.EXPECT().ShowCollections(mock.Anything, mock.Anything).Return(&querypb.ShowCollectionsResponse{}, nil).Maybe()
+		rootCoord.EXPECT().ListPolicy(mock.Anything, mock.Anything, mock.Anything).Return(&internalpb.ListPolicyResponse{Status: merr.Success()}, nil).Once()
+		mgr := newShardClientMgr()
+		err := InitMetaCache(ctx, rootCoord, queryCoord, mgr)
+		assert.NoError(t, err)
+	})
+
+	t.Run("failed to list policy", func(t *testing.T) {
+		ctx := context.Background()
+		rootCoord := mocks.NewMockRootCoordClient(t)
+		queryCoord := mocks.NewMockQueryCoordClient(t)
+		rootCoord.EXPECT().ListPolicy(mock.Anything, mock.Anything, mock.Anything).Return(
+			&internalpb.ListPolicyResponse{Status: merr.Status(errors.New("mock list policy error"))},
+			nil).Once()
+		mgr := newShardClientMgr()
+		err := InitMetaCache(ctx, rootCoord, queryCoord, mgr)
+		assert.Error(t, err)
+	})
+
+	t.Run("rpc error", func(t *testing.T) {
+		ctx := context.Background()
+		rootCoord := mocks.NewMockRootCoordClient(t)
+		queryCoord := mocks.NewMockQueryCoordClient(t)
+		rootCoord.EXPECT().ListPolicy(mock.Anything, mock.Anything, mock.Anything).Return(
+			nil, errors.New("mock list policy rpc errorr")).Once()
+		mgr := newShardClientMgr()
+		err := InitMetaCache(ctx, rootCoord, queryCoord, mgr)
+		assert.Error(t, err)
+	})
+}
+
 func TestMetaCache_GetCollectionName(t *testing.T) {
 	ctx := context.Background()
 	rootCoord := &MockRootCoordClientInterface{}