*: fix variable problem during initialization (#38971) (#38976)

close #38973
pingcap · Nov 9, 2022 · 274d9c5 · 274d9c5
1 parent 786e3b4
commit 274d9c5
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Showing 3 changed files with 11 additions and 4 deletions.
diff --git a/sessionctx/variable/BUILD.bazel b/sessionctx/variable/BUILD.bazel
@@ -85,6 +85,7 @@ go_test(
     ],
     embed = [":variable"],
     flaky = True,
+    shard_count = 2,
     deps = [
         "//config",
         "//kv",

diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
@@ -746,7 +746,8 @@ var defaultSysVars = []*SysVar{
 			if floatValue < 0 && floatValue > 0.9 {
 				return "", ErrWrongValueForVar.GenWithStackByArgs(TiDBGOGCTunerThreshold, normalizedValue)
 			}
-			if globalMemoryLimitTuner < floatValue+0.05 {
+			// globalMemoryLimitTuner must not be 0. it will be 0 when tidb_server_memory_limit_gc_trigger is not set during startup.
+			if globalMemoryLimitTuner != 0 && globalMemoryLimitTuner < floatValue+0.05 {
 				return "", errors.New("tidb_gogc_tuner_threshold should be less than tidb_server_memory_limit_gc_trigger - 0.05")
 			}
 			return strconv.FormatFloat(floatValue, 'f', -1, 64), nil
@@ -837,7 +838,8 @@ var defaultSysVars = []*SysVar{
 			if floatValue < 0.51 && floatValue > 1 { // 51% ~ 100%
 				return "", ErrWrongValueForVar.GenWithStackByArgs(TiDBServerMemoryLimitGCTrigger, normalizedValue)
 			}
-			if floatValue < gogcTunerThreshold+0.05 {
+			// gogcTunerThreshold must not be 0. it will be 0 when tidb_gogc_tuner_threshold is not set during startup.
+			if gogcTunerThreshold != 0 && floatValue < gogcTunerThreshold+0.05 {
 				return "", errors.New("tidb_server_memory_limit_gc_trigger should be greater than tidb_gogc_tuner_threshold + 0.05")
 			}
 

diff --git a/sessionctx/variable/variable_test.go b/sessionctx/variable/variable_test.go
@@ -436,18 +436,22 @@ func TestDefaultValuesAreSettable(t *testing.T) {
 	for _, sv := range GetSysVars() {
 		if sv.HasSessionScope() && !sv.ReadOnly {
 			val, err := sv.Validate(vars, sv.Value, ScopeSession)
-			require.Equal(t, val, sv.Value)
 			require.NoError(t, err)
+			require.Equal(t, val, sv.Value)
 		}
 
 		if sv.HasGlobalScope() && !sv.ReadOnly {
 			val, err := sv.Validate(vars, sv.Value, ScopeGlobal)
-			require.Equal(t, val, sv.Value)
 			require.NoError(t, err)
+			require.Equal(t, val, sv.Value)
 		}
 	}
 }
 
+func TestLimitBetweenVariable(t *testing.T) {
+	require.Less(t, DefTiDBGOGCTunerThreshold+0.05, DefTiDBServerMemoryLimitGCTrigger)
+}
+
 // TestSysVarNameIsLowerCase tests that no new sysvars are added with uppercase characters.
 // In MySQL variables are always lowercase, and can be set in a case-insensitive way.
 func TestSysVarNameIsLowerCase(t *testing.T) {