config: fix the panic caused by zero RegionSplitSizeMB (#8324)

pkg/typeutil/size_test.go

@@ -40,25 +40,33 @@ func TestSizeJSON(t *testing.T) {
 }
 
 func TestParseMbFromText(t *testing.T) {
+	const defaultValue = 2
+
 	t.Parallel()
 	re := require.New(t)
 	testCases := []struct {
 		body []string
 		size uint64
 	}{{
 		body: []string{"10Mib", "10MiB", "10M", "10MB"},
-		size: uint64(10),
+		size: 10,
 	}, {
 		body: []string{"10GiB", "10Gib", "10G", "10GB"},
-		size: uint64(10 * units.GiB / units.MiB),
+		size: 10 * units.GiB / units.MiB,
+	}, {
+		body: []string{"1024KiB", "1048576"},
+		size: 1,
+	}, {
+		body: []string{"100KiB", "1023KiB", "1048575", "0"},
+		size: 0,
 	}, {
 		body: []string{"10yiB", "10aib"},
-		size: uint64(1),
+		size: defaultValue,
 	}}
 
 	for _, testCase := range testCases {
 		for _, b := range testCase.body {
-			re.Equal(int(testCase.size), int(ParseMBFromText(b, 1)))
+			re.Equal(testCase.size, ParseMBFromText(b, defaultValue))
 		}
 	}
 }

server/config/store_config.go

@@ -141,9 +141,14 @@ func (c *StoreConfig) CheckRegionSize(size, mergeSize uint64) error {
 	if size < c.GetRegionMaxSize() {
 		return nil
 	}
-
+	// This could happen when the region split size is set to a value less than 1MiB,
+	// which is a very extreme case, we just pass the check here to prevent panic.
+	regionSplitSize := c.GetRegionSplitSize()
+	if regionSplitSize == 0 {
+		return nil
+	}
 	// the smallest of the split regions can not be merge again, so it's size should less merge size.
-	if smallSize := size % c.GetRegionSplitSize(); smallSize <= mergeSize && smallSize != 0 {
+	if smallSize := size % regionSplitSize; smallSize <= mergeSize && smallSize != 0 {
 		log.Debug("region size is too small", zap.Uint64("size", size), zap.Uint64("merge-size", mergeSize), zap.Uint64("small-size", smallSize))
 		return errs.ErrCheckerMergeAgain.FastGenByArgs("the smallest region of the split regions is less than max-merge-region-size, " +
 			"it will be merged again")

server/config/store_config_test.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/docker/go-units"
 	"github.com/stretchr/testify/require"
+	"github.com/tikv/pd/pkg/typeutil"
 )
 
 func TestTiKVConfig(t *testing.T) {
@@ -158,4 +159,9 @@ func TestMergeCheck(t *testing.T) {
 			re.Error(config.CheckRegionKeys(v.keys, v.mergeKeys))
 		}
 	}
+	// Test CheckRegionSize when the region split size is 0.
+	config.RegionSplitSize = "100KiB"
+	config.RegionSplitSizeMB = typeutil.ParseMBFromText(config.RegionSplitSize, defaultRegionSplitSize)
+	re.Empty(config.GetRegionSplitSize())
+	re.NoError(config.CheckRegionSize(defaultRegionMaxSize, 50))
 }