TiDBLogFileMaxDays and TiDBConfig should be ScopeInstance

[morgo]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

From manual inspection of code:

tidb/sessionctx/variable/sysvar.go

Lines 203 to 225 in 11e1f14

	{Scope: ScopeSession, Name: TiDBLogFileMaxDays, Value: strconv.Itoa(config.GetGlobalConfig().Log.File.MaxDays), Type: TypeInt, MinValue: 0, MaxValue: math.MaxInt32, skipInit: true, SetSession: func(s *SessionVars, val string) error {
	maxAge, err := strconv.ParseInt(val, 10, 32)
	if err != nil {
	return err
	}
	GlobalLogMaxDays.Store(int32(maxAge))
	cfg := config.GetGlobalConfig().Log.ToLogConfig()
	cfg.Config.File.MaxDays = int(maxAge)
	err = logutil.ReplaceLogger(cfg)
	if err != nil {
	return err
	}
	return nil
	}, GetSession: func(s *SessionVars) (string, error) {
	return strconv.FormatInt(int64(GlobalLogMaxDays.Load()), 10), nil
	}},
	{Scope: ScopeSession, Name: TiDBConfig, Value: "", ReadOnly: true, skipInit: true, GetSession: func(s *SessionVars) (string, error) {
	return config.GetJSONConfig()
	}},

2. What did you expect to see? (Required)

These sysvars should be instance scoped. They have no relation to the current session.

3. What did you see instead (Required)

See above

4. What is your TiDB version? (Required)

master

[bb7133]

There was no instance scoped variables at the time tidb_log_file_max_days was introduced, so I would treat this issue as 'enhancement'.