add more fail point tests

Signed-off-by: Zhigao Tong <tongzhigao@pingcap.com>

executor/tiflashtest/tiflash_test.go

@@ -1580,6 +1580,7 @@ func TestMppStoreCntWithErrors(t *testing.T) {
 	var mppStoreCountPDError = "github.com/pingcap/tidb/store/copr/mppStoreCountPDError"
 	var mppStoreCountSetMPPCnt = "github.com/pingcap/tidb/store/copr/mppStoreCountSetMPPCnt"
 	var mppStoreCountSetLastUpdateTime = "github.com/pingcap/tidb/store/copr/mppStoreCountSetLastUpdateTime"
+	var mppStoreCountSetLastUpdateTimeP2 = "github.com/pingcap/tidb/store/copr/mppStoreCountSetLastUpdateTimeP2"
 
 	store := testkit.CreateMockStore(t, withMockTiFlash(3))
 	{
@@ -1616,6 +1617,17 @@ func TestMppStoreCntWithErrors(t *testing.T) {
 		// still update cache
 		require.Equal(t, mppCnt, 2222)
 	}
+	require.Nil(t, failpoint.Enable(mppStoreCountSetLastUpdateTime, `return("1")`))
+	// fail to get lock and old cache
+	require.Nil(t, failpoint.Enable(mppStoreCountSetLastUpdateTimeP2, `return("2")`))
+	require.Nil(t, failpoint.Enable(mppStoreCountPDError, `return(true)`))
+	{
+		mppCnt, err := store.GetMPPClient().GetMPPStoreCount()
+		require.Nil(t, err)
+		require.Equal(t, mppCnt, 2222)
+	}
 	require.Nil(t, failpoint.Disable(mppStoreCountSetMPPCnt))
 	require.Nil(t, failpoint.Disable(mppStoreCountSetLastUpdateTime))
+	require.Nil(t, failpoint.Disable(mppStoreCountSetLastUpdateTimeP2))
+	require.Nil(t, failpoint.Disable(mppStoreCountPDError))
 }

store/copr/mpp.go

@@ -583,22 +583,27 @@ func (c *MPPClient) DispatchMPPTasks(ctx context.Context, variables interface{},
 }
 
 func (c *mppStoreCnt) getMPPStoreCount(storeCtx *kvStore, TTL int64) (int, error) {
+	failpoint.Inject("mppStoreCountSetLastUpdateTime", func(value failpoint.Value) {
+		v, _ := strconv.ParseInt(value.(string), 10, 0)
+		c.lastUpdate = v
+	})
+
 	lastUpdate := atomic.LoadInt64(&c.lastUpdate)
 	oriMPPStoreCnt := atomic.LoadInt32(&c.cnt)
 	now := time.Now().UnixMicro()
 	isInit := atomic.LoadInt32(&c.initFlag) != 0
 
-	failpoint.Inject("mppStoreCountSetLastUpdateTime", func(value failpoint.Value) {
-		v, _ := strconv.ParseInt(value.(string), 10, 0)
-		lastUpdate = v
-		c.lastUpdate = lastUpdate
-	})
-
 	if now-lastUpdate < TTL {
 		if isInit {
 			return int(oriMPPStoreCnt), nil
 		}
 	}
+
+	failpoint.Inject("mppStoreCountSetLastUpdateTimeP2", func(value failpoint.Value) {
+		v, _ := strconv.ParseInt(value.(string), 10, 0)
+		c.lastUpdate = v
+	})
+
 	if !atomic.CompareAndSwapInt64(&c.lastUpdate, lastUpdate, now) {
 		if isInit {
 			return int(oriMPPStoreCnt), nil