From 9d19be16040ca409e31a81b2c86f2d23d3651e18 Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Thu, 16 Jun 2022 17:21:45 +0800
Subject: [PATCH 1/6] config, sysvar: map `max-server-connections` to
 `max_connections`

---
 config/config.go                 |  3 +++
 config/config.toml.example       |  6 +++---
 config/config_test.go            | 15 +++++++++------
 server/server.go                 | 30 +++++++++++++++++++++++++-----
 sessionctx/variable/noop.go      |  1 -
 sessionctx/variable/sysvar.go    | 10 ++++++++++
 sessionctx/variable/tidb_vars.go |  2 ++
 tidb-server/main.go              |  2 ++
 8 files changed, 54 insertions(+), 15 deletions(-)

diff --git a/config/config.go b/config/config.go
index a701b1501bf15..4c3b2d5c7b764 100644
--- a/config/config.go
+++ b/config/config.go
@@ -117,6 +117,7 @@ var (
 			map[string]string{
 				"check-mb4-value-in-utf8":       "tidb_check_mb4_value_in_utf8",
 				"enable-collect-execution-info": "tidb_enable_collect_execution_info",
+				"max-server-connections":        "max_connections",
 			},
 		},
 		{
@@ -473,6 +474,7 @@ type Instance struct {
 	EnableCollectExecutionInfo bool   `toml:"tidb_enable_collect_execution_info" json:"tidb_enable_collect_execution_info"`
 	PluginDir                  string `toml:"plugin_dir" json:"plugin_dir"`
 	PluginLoad                 string `toml:"plugin_load" json:"plugin_load"`
+	MaxConnections             uint32 `toml:"max_connections" json:"max_connections"`
 }
 
 func (l *Log) getDisableTimestamp() bool {
@@ -824,6 +826,7 @@ var defaultConf = Config{
 		EnableCollectExecutionInfo:  true,
 		PluginDir:                   "/data/deploy/plugin",
 		PluginLoad:                  "",
+		MaxConnections:              0,
 	},
 	Status: Status{
 		ReportStatus:          true,
diff --git a/config/config.toml.example b/config/config.toml.example
index e23f390e23efb..2e5eaaff24b38 100644
--- a/config/config.toml.example
+++ b/config/config.toml.example
@@ -89,9 +89,6 @@ repair-mode = false
 # In repair mode, repairing table which is not in repair list will get wrong database or wrong table error.
 repair-table-list = []
 
-# The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
-max-server-connections = 0
-
 # Whether new collations are enabled, as indicated by its name, this configuration entry take effect ONLY when a TiDB cluster bootstraps for the first time.
 new_collations_enabled_on_first_bootstrap = true
 
@@ -465,3 +462,6 @@ tidb_slow_log_threshold = 300
 # tidb_record_plan_in_slow_log is used to enable record query plan in slow log.
 # 0 is disable. 1 is enable.
 tidb_record_plan_in_slow_log = 1
+
+# The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
+max_connections = 0
diff --git a/config/config_test.go b/config/config_test.go
index 391bd874d3942..2e044062bd4e8 100644
--- a/config/config_test.go
+++ b/config/config_test.go
@@ -282,9 +282,6 @@ repair-mode = false
 # In repair mode, repairing table which is not in repair list will get wrong database or wrong table error.
 repair-table-list = []
 
-# The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
-max-server-connections = 0
-
 # Whether new collations are enabled, as indicated by its name, this configuration entry take effect ONLY when a TiDB cluster bootstraps for the first time.
 new_collations_enabled_on_first_bootstrap = true
 
@@ -309,6 +306,11 @@ deprecate-integer-display-length = false
 # See https://dev.mysql.com/doc/refman/8.0/en/string-type-syntax.html for more details.
 enable-enum-length-limit = true
 
+[instance]
+
+# The maximum permitted number of simultaneous client connections. When the value is 0, the number of connections is unlimited.
+max_connections = 0
+
 [log]
 # Log level: debug, info, warn, error, fatal.
 level = "info"
@@ -707,7 +709,7 @@ unrecognized-option-test = true
 	match, err := regexp.Match("(?:.|\n)*invalid configuration option(?:.|\n)*", []byte(err.Error()))
 	require.NoError(t, err)
 	require.True(t, match)
-	require.Equal(t, uint32(0), conf.MaxServerConnections)
+	require.Equal(t, uint32(0), conf.Instance.MaxConnections)
 
 	err = f.Truncate(0)
 	require.NoError(t, err)
@@ -722,7 +724,6 @@ delay-clean-table-lock = 5
 split-region-max-num=10000
 server-version = "test_version"
 repair-mode = true
-max-server-connections = 200
 max-index-length = 3080
 index-limit = 70
 table-column-count-limit = 4000
@@ -768,6 +769,8 @@ grpc-keepalive-timeout = 10
 grpc-concurrent-streams = 2048
 grpc-initial-window-size = 10240
 grpc-max-send-msg-size = 40960
+[instance]
+max_connections = 200
 `)
 
 	require.NoError(t, err)
@@ -797,7 +800,7 @@ grpc-max-send-msg-size = 40960
 	require.Equal(t, uint64(10000), conf.SplitRegionMaxNum)
 	require.True(t, conf.RepairMode)
 	require.Equal(t, uint64(16), conf.TiKVClient.ResolveLockLiteThreshold)
-	require.Equal(t, uint32(200), conf.MaxServerConnections)
+	require.Equal(t, uint32(200), conf.Instance.MaxConnections)
 	require.Equal(t, []string{"tiflash"}, conf.IsolationRead.Engines)
 	require.Equal(t, 3080, conf.MaxIndexLength)
 	require.Equal(t, 70, conf.IndexLimit)
diff --git a/server/server.go b/server/server.go
index 90b4a7e27101b..86f49884d4ab1 100644
--- a/server/server.go
+++ b/server/server.go
@@ -302,6 +302,7 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 	rand.Seed(time.Now().UTC().UnixNano())
 
 	variable.RegisterStatistics(s)
+	variable.SetMaxConnections = s.SetMaxConnections
 
 	return s, nil
 }
@@ -352,7 +353,7 @@ func setTxnScope() {
 // Export config-related metrics
 func (s *Server) reportConfig() {
 	metrics.ConfigStatus.WithLabelValues("token-limit").Set(float64(s.cfg.TokenLimit))
-	metrics.ConfigStatus.WithLabelValues("max-server-connections").Set(float64(s.cfg.MaxServerConnections))
+	metrics.ConfigStatus.WithLabelValues("max_connections").Set(float64(s.cfg.Instance.MaxConnections))
 }
 
 // Run runs the server.
@@ -605,8 +606,8 @@ func (cc *clientConn) connectInfo() *variable.ConnectionInfo {
 }
 
 func (s *Server) checkConnectionCount() error {
-	// When the value of MaxServerConnections is 0, the number of connections is unlimited.
-	if int(s.cfg.MaxServerConnections) == 0 {
+	// When the value of Instance.MaxConnections is 0, the number of connections is unlimited.
+	if int(s.cfg.Instance.MaxConnections) == 0 {
 		return nil
 	}
 
@@ -614,9 +615,28 @@ func (s *Server) checkConnectionCount() error {
 	conns := len(s.clients)
 	s.rwlock.RUnlock()
 
-	if conns >= int(s.cfg.MaxServerConnections) {
+	if conns >= int(s.cfg.Instance.MaxConnections) {
 		logutil.BgLogger().Error("too many connections",
-			zap.Uint32("max connections", s.cfg.MaxServerConnections), zap.Error(errConCount))
+			zap.Uint32("max connections", s.cfg.Instance.MaxConnections), zap.Error(errConCount))
+		return errConCount
+	}
+	return nil
+}
+
+// SetMaxConnections checks and updates the value of max_connections.
+func (s *Server) SetMaxConnections(newMaxConnections uint32) error {
+	// When the value of newMaxConnections is 0, the number of connections is unlimited.
+	if int(newMaxConnections) == 0 {
+		return nil
+	}
+
+	s.rwlock.RLock()
+	conns := len(s.clients)
+	s.rwlock.RUnlock()
+
+	if conns >= int(newMaxConnections) {
+		logutil.BgLogger().Error("Current connections number exceeds the setting value",
+			zap.Uint32("max connections", newMaxConnections), zap.Error(errConCount))
 		return errConCount
 	}
 	return nil
diff --git a/sessionctx/variable/noop.go b/sessionctx/variable/noop.go
index 4f2cdac1aa690..6eb70beabfc99 100644
--- a/sessionctx/variable/noop.go
+++ b/sessionctx/variable/noop.go
@@ -24,7 +24,6 @@ import (
 // but changing them has no effect on behavior.
 
 var noopSysVars = []*SysVar{
-	{Scope: ScopeGlobal, Name: MaxConnections, Value: "151", Type: TypeUnsigned, MinValue: 1, MaxValue: 100000},
 	// It is unsafe to pretend that any variation of "read only" is enabled when the server
 	// does not support it. It is possible that these features will be supported in future,
 	// but until then...
diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
index 06e206c98ab8a..9506bdb0c4223 100644
--- a/sessionctx/variable/sysvar.go
+++ b/sessionctx/variable/sysvar.go
@@ -415,6 +415,16 @@ var defaultSysVars = []*SysVar{
 	{Scope: ScopeInstance, Name: PluginDir, Value: "/data/deploy/plugin", ReadOnly: true, GetGlobal: func(s *SessionVars) (string, error) {
 		return config.GetGlobalConfig().Instance.PluginDir, nil
 	}},
+	{Scope: ScopeInstance, Name: MaxConnections, Value: strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), Type: TypeUnsigned, MinValue: 0, MaxValue: math.MaxUint32, SetGlobal: func(s *SessionVars, val string) error {
+		newVal := uint32(TidbOptInt64(val, 0))
+		if err := SetMaxConnections(newVal); err != nil {
+			return err
+		}
+		config.GetGlobalConfig().Instance.MaxConnections = newVal
+		return nil
+	}, GetGlobal: func(s *SessionVars) (string, error) {
+		return strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), nil
+	}},
 
 	/* The system variables below have GLOBAL scope  */
 	{Scope: ScopeGlobal, Name: MaxPreparedStmtCount, Value: strconv.FormatInt(DefMaxPreparedStmtCount, 10), Type: TypeInt, MinValue: -1, MaxValue: 1048576},
diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
index 64c1916292c73..c2e9356d7d8d2 100644
--- a/sessionctx/variable/tidb_vars.go
+++ b/sessionctx/variable/tidb_vars.go
@@ -994,4 +994,6 @@ var (
 	GetMemQuotaAnalyze func() int64 = nil
 	// SetStatsCacheCapacity is the func registered by domain to set statsCache memory quota.
 	SetStatsCacheCapacity atomic.Value
+	// SetMaxConnections is the func registered by derver to set the value of max_connections.
+	SetMaxConnections func(newMaxConnections uint32) error = nil
 )
diff --git a/tidb-server/main.go b/tidb-server/main.go
index 40dd3cacfd5a1..10c3245eccdf8 100644
--- a/tidb-server/main.go
+++ b/tidb-server/main.go
@@ -558,6 +558,8 @@ func setGlobalVars() {
 					cfg.Instance.CheckMb4ValueInUTF8.Store(cfg.CheckMb4ValueInUTF8.Load())
 				case "enable-collect-execution-info":
 					cfg.Instance.EnableCollectExecutionInfo = cfg.EnableCollectExecutionInfo
+				case "max-server-connections":
+					cfg.Instance.MaxConnections = cfg.MaxServerConnections
 				}
 			case "log":
 				switch oldName {

From 67ff2ad09494f52debe10194ad6f5891a9b35fff Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Thu, 16 Jun 2022 20:58:19 +0800
Subject: [PATCH 2/6] Fix UT fails.

---
 executor/set_test.go           | 13 +++++++------
 expression/integration_test.go |  4 ++--
 sessionctx/variable/sysvar.go  |  8 +++++---
 3 files changed, 14 insertions(+), 11 deletions(-)

diff --git a/executor/set_test.go b/executor/set_test.go
index 4f0151b6d2129..1a9acb0e6e989 100644
--- a/executor/set_test.go
+++ b/executor/set_test.go
@@ -914,16 +914,17 @@ func TestValidateSetVar(t *testing.T) {
 	result.Check(testkit.Rows("SYSTEM"))
 
 	// The following cases test value out of range and illegal type when setting system variables.
-	// See https://dev.mysql.com/doc/refman/5.7/en/server-system-variables.html for more details.
+	// See https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html for more details.
 	tk.MustExec("set @@global.max_connections=100001")
 	tk.MustQuery("show warnings").Check(testkit.RowsWithSep("|", "Warning|1292|Truncated incorrect max_connections value: '100001'"))
 	result = tk.MustQuery("select @@global.max_connections;")
 	result.Check(testkit.Rows("100000"))
 
+	// "max_connections == 0" means there is no limitation on the number of connections.
 	tk.MustExec("set @@global.max_connections=-1")
 	tk.MustQuery("show warnings").Check(testkit.RowsWithSep("|", "Warning|1292|Truncated incorrect max_connections value: '-1'"))
 	result = tk.MustQuery("select @@global.max_connections;")
-	result.Check(testkit.Rows("1"))
+	result.Check(testkit.Rows("0"))
 
 	err = tk.ExecToErr("set @@global.max_connections='hello'")
 	require.True(t, terror.ErrorEqual(err, variable.ErrWrongTypeForVar))
@@ -970,7 +971,7 @@ func TestValidateSetVar(t *testing.T) {
 	tk.MustExec("set @@global.max_connections=-1")
 	tk.MustQuery("show warnings").Check(testkit.RowsWithSep("|", "Warning|1292|Truncated incorrect max_connections value: '-1'"))
 	result = tk.MustQuery("select @@global.max_connections;")
-	result.Check(testkit.Rows("1"))
+	result.Check(testkit.Rows("0"))
 
 	err = tk.ExecToErr("set @@global.max_connections='hello'")
 	require.True(t, terror.ErrorEqual(err, variable.ErrWrongTypeForVar))
@@ -1226,15 +1227,15 @@ func TestSelectGlobalVar(t *testing.T) {
 	defer clean()
 	tk := testkit.NewTestKit(t, store)
 
-	tk.MustQuery("select @@global.max_connections;").Check(testkit.Rows("151"))
-	tk.MustQuery("select @@max_connections;").Check(testkit.Rows("151"))
+	tk.MustQuery("select @@global.max_connections;").Check(testkit.Rows("0"))
+	tk.MustQuery("select @@max_connections;").Check(testkit.Rows("0"))
 
 	tk.MustExec("set @@global.max_connections=100;")
 
 	tk.MustQuery("select @@global.max_connections;").Check(testkit.Rows("100"))
 	tk.MustQuery("select @@max_connections;").Check(testkit.Rows("100"))
 
-	tk.MustExec("set @@global.max_connections=151;")
+	tk.MustExec("set @@global.max_connections=0;")
 
 	// test for unknown variable.
 	err := tk.ExecToErr("select @@invalid")
diff --git a/expression/integration_test.go b/expression/integration_test.go
index 53be8080bb6fd..5b8d81a8a36a5 100644
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -6212,11 +6212,11 @@ func TestGlobalCacheCorrectness(t *testing.T) {
 	defer clean()
 
 	tk := testkit.NewTestKit(t, store)
-	tk.MustQuery("SHOW VARIABLES LIKE 'max_connections'").Check(testkit.Rows("max_connections 151"))
+	tk.MustQuery("SHOW VARIABLES LIKE 'max_connections'").Check(testkit.Rows("max_connections 0"))
 	tk.MustExec("SET GLOBAL max_connections=1234")
 	tk.MustQuery("SHOW VARIABLES LIKE 'max_connections'").Check(testkit.Rows("max_connections 1234"))
 	// restore
-	tk.MustExec("SET GLOBAL max_connections=151")
+	tk.MustExec("SET GLOBAL max_connections=0")
 }
 
 func TestRedundantColumnResolve(t *testing.T) {
diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
index 9506bdb0c4223..fd870e912c8d6 100644
--- a/sessionctx/variable/sysvar.go
+++ b/sessionctx/variable/sysvar.go
@@ -415,10 +415,12 @@ var defaultSysVars = []*SysVar{
 	{Scope: ScopeInstance, Name: PluginDir, Value: "/data/deploy/plugin", ReadOnly: true, GetGlobal: func(s *SessionVars) (string, error) {
 		return config.GetGlobalConfig().Instance.PluginDir, nil
 	}},
-	{Scope: ScopeInstance, Name: MaxConnections, Value: strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), Type: TypeUnsigned, MinValue: 0, MaxValue: math.MaxUint32, SetGlobal: func(s *SessionVars, val string) error {
+	{Scope: ScopeInstance, Name: MaxConnections, Value: strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), Type: TypeUnsigned, MinValue: 0, MaxValue: 100000, SetGlobal: func(s *SessionVars, val string) error {
 		newVal := uint32(TidbOptInt64(val, 0))
-		if err := SetMaxConnections(newVal); err != nil {
-			return err
+		if SetMaxConnections != nil {
+			if err := SetMaxConnections(newVal); err != nil {
+				return err
+			}
 		}
 		config.GetGlobalConfig().Instance.MaxConnections = newVal
 		return nil

From 1015d5350fbfe63eb129c2b05664484b9f647e32 Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Thu, 16 Jun 2022 23:44:38 +0800
Subject: [PATCH 3/6] Fix

---
 server/server.go                 | 2 +-
 sessionctx/variable/tidb_vars.go | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/server/server.go b/server/server.go
index 86f49884d4ab1..e4a009f7f1937 100644
--- a/server/server.go
+++ b/server/server.go
@@ -634,7 +634,7 @@ func (s *Server) SetMaxConnections(newMaxConnections uint32) error {
 	conns := len(s.clients)
 	s.rwlock.RUnlock()
 
-	if conns >= int(newMaxConnections) {
+	if conns > int(newMaxConnections) {
 		logutil.BgLogger().Error("Current connections number exceeds the setting value",
 			zap.Uint32("max connections", newMaxConnections), zap.Error(errConCount))
 		return errConCount
diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
index c2e9356d7d8d2..657e88d161398 100644
--- a/sessionctx/variable/tidb_vars.go
+++ b/sessionctx/variable/tidb_vars.go
@@ -994,6 +994,6 @@ var (
 	GetMemQuotaAnalyze func() int64 = nil
 	// SetStatsCacheCapacity is the func registered by domain to set statsCache memory quota.
 	SetStatsCacheCapacity atomic.Value
-	// SetMaxConnections is the func registered by derver to set the value of max_connections.
+	// SetMaxConnections is the func registered by server to set the value of max_connections.
 	SetMaxConnections func(newMaxConnections uint32) error = nil
 )

From 8a0a06dac9d397cfa337f7c2e1a388412d082b2b Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Mon, 20 Jun 2022 20:11:47 +0800
Subject: [PATCH 4/6] Change error information

---
 server/server.go                 | 27 +++++----------------------
 sessionctx/variable/sysvar.go    |  8 +-------
 sessionctx/variable/tidb_vars.go |  2 --
 3 files changed, 6 insertions(+), 31 deletions(-)

diff --git a/server/server.go b/server/server.go
index e4a009f7f1937..aa5a5f744d38b 100644
--- a/server/server.go
+++ b/server/server.go
@@ -302,7 +302,6 @@ func NewServer(cfg *config.Config, driver IDriver) (*Server, error) {
 	rand.Seed(time.Now().UTC().UnixNano())
 
 	variable.RegisterStatistics(s)
-	variable.SetMaxConnections = s.SetMaxConnections
 
 	return s, nil
 }
@@ -515,11 +514,14 @@ func (s *Server) onConn(conn *clientConn) {
 			})
 			terror.Log(err)
 		}
-		if errors.Cause(err) == io.EOF {
+		switch errors.Cause(err) {
+		case io.EOF:
 			// `EOF` means the connection is closed normally, we do not treat it as a noticeable error and log it in 'DEBUG' level.
 			logutil.BgLogger().With(zap.Uint64("conn", conn.connectionID)).
 				Debug("EOF", zap.String("remote addr", conn.bufReadConn.RemoteAddr().String()))
-		} else {
+		case errConCount:
+			_ = conn.writeError(ctx, err)
+		default:
 			metrics.HandShakeErrorCounter.Inc()
 			logutil.BgLogger().With(zap.Uint64("conn", conn.connectionID)).
 				Warn("Server.onConn handshake", zap.Error(err),
@@ -623,25 +625,6 @@ func (s *Server) checkConnectionCount() error {
 	return nil
 }
 
-// SetMaxConnections checks and updates the value of max_connections.
-func (s *Server) SetMaxConnections(newMaxConnections uint32) error {
-	// When the value of newMaxConnections is 0, the number of connections is unlimited.
-	if int(newMaxConnections) == 0 {
-		return nil
-	}
-
-	s.rwlock.RLock()
-	conns := len(s.clients)
-	s.rwlock.RUnlock()
-
-	if conns > int(newMaxConnections) {
-		logutil.BgLogger().Error("Current connections number exceeds the setting value",
-			zap.Uint32("max connections", newMaxConnections), zap.Error(errConCount))
-		return errConCount
-	}
-	return nil
-}
-
 // ShowProcessList implements the SessionManager interface.
 func (s *Server) ShowProcessList() map[uint64]*util.ProcessInfo {
 	rs := make(map[uint64]*util.ProcessInfo)
diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
index fd870e912c8d6..01879fde2943c 100644
--- a/sessionctx/variable/sysvar.go
+++ b/sessionctx/variable/sysvar.go
@@ -416,13 +416,7 @@ var defaultSysVars = []*SysVar{
 		return config.GetGlobalConfig().Instance.PluginDir, nil
 	}},
 	{Scope: ScopeInstance, Name: MaxConnections, Value: strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), Type: TypeUnsigned, MinValue: 0, MaxValue: 100000, SetGlobal: func(s *SessionVars, val string) error {
-		newVal := uint32(TidbOptInt64(val, 0))
-		if SetMaxConnections != nil {
-			if err := SetMaxConnections(newVal); err != nil {
-				return err
-			}
-		}
-		config.GetGlobalConfig().Instance.MaxConnections = newVal
+		config.GetGlobalConfig().Instance.MaxConnections = uint32(TidbOptInt64(val, 0))
 		return nil
 	}, GetGlobal: func(s *SessionVars) (string, error) {
 		return strconv.FormatUint(uint64(config.GetGlobalConfig().Instance.MaxConnections), 10), nil
diff --git a/sessionctx/variable/tidb_vars.go b/sessionctx/variable/tidb_vars.go
index 657e88d161398..64c1916292c73 100644
--- a/sessionctx/variable/tidb_vars.go
+++ b/sessionctx/variable/tidb_vars.go
@@ -994,6 +994,4 @@ var (
 	GetMemQuotaAnalyze func() int64 = nil
 	// SetStatsCacheCapacity is the func registered by domain to set statsCache memory quota.
 	SetStatsCacheCapacity atomic.Value
-	// SetMaxConnections is the func registered by server to set the value of max_connections.
-	SetMaxConnections func(newMaxConnections uint32) error = nil
 )

From 50017824b288d00d7704062691cb8843ef292d9f Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Wed, 22 Jun 2022 16:00:39 +0800
Subject: [PATCH 5/6] Add error handlinr in server.go

---
 server/server.go | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/server/server.go b/server/server.go
index aa5a5f744d38b..b657b2ef9a81e 100644
--- a/server/server.go
+++ b/server/server.go
@@ -47,7 +47,6 @@ import (
 	"time"
 	"unsafe"
 
-	"github.com/blacktear23/go-proxyprotocol"
 	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/domain"
@@ -520,7 +519,11 @@ func (s *Server) onConn(conn *clientConn) {
 			logutil.BgLogger().With(zap.Uint64("conn", conn.connectionID)).
 				Debug("EOF", zap.String("remote addr", conn.bufReadConn.RemoteAddr().String()))
 		case errConCount:
-			_ = conn.writeError(ctx, err)
+			if err := conn.writeError(ctx, err); err != nil {
+				logutil.BgLogger().With(zap.Uint64("conn", conn.connectionID)).
+					Warn("error in writing errConCount", zap.Error(err),
+						zap.String("remote addr", conn.bufReadConn.RemoteAddr().String()))
+			}
 		default:
 			metrics.HandShakeErrorCounter.Inc()
 			logutil.BgLogger().With(zap.Uint64("conn", conn.connectionID)).

From d6724625ded8cb009b1985c3b2337ce41afe4a3a Mon Sep 17 00:00:00 2001
From: cbcwestwolf <1004626265@qq.com>
Date: Wed, 22 Jun 2022 16:14:26 +0800
Subject: [PATCH 6/6] Fix

---
 server/server.go | 1 +
 1 file changed, 1 insertion(+)

diff --git a/server/server.go b/server/server.go
index b657b2ef9a81e..13ed052391f59 100644
--- a/server/server.go
+++ b/server/server.go
@@ -47,6 +47,7 @@ import (
 	"time"
 	"unsafe"
 
+	"github.com/blacktear23/go-proxyprotocol"
 	"github.com/pingcap/errors"
 	"github.com/pingcap/tidb/config"
 	"github.com/pingcap/tidb/domain"