config: add configuration entry make TiDB version string configurable (#13775)

config/config.go

@@ -29,6 +29,7 @@ import (
 	"github.com/BurntSushi/toml"
 	"github.com/pingcap/errors"
 	zaplog "github.com/pingcap/log"
+	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/util/logutil"
 	tracing "github.com/uber/jaeger-client-go/config"
 	"go.uber.org/atomic"
@@ -74,8 +75,8 @@ type Config struct {
 	TxnLocalLatches  TxnLocalLatches `toml:"txn-local-latches" json:"txn-local-latches"`
 	// Set sys variable lower-case-table-names, ref: https://dev.mysql.com/doc/refman/5.7/en/identifier-case-sensitivity.html.
 	// TODO: We actually only support mode 2, which keeps the original case, but the comparison is case-insensitive.
-	LowerCaseTableNames int `toml:"lower-case-table-names" json:"lower-case-table-names"`
-
+	LowerCaseTableNames int               `toml:"lower-case-table-names" json:"lower-case-table-names"`
+	ServerVersion       string            `toml:"server-version" json:"server-version"`
 	Log                 Log               `toml:"log" json:"log"`
 	Security            Security          `toml:"security" json:"security"`
 	Status              Status            `toml:"status" json:"status"`
@@ -450,6 +451,7 @@ var defaultConf = Config{
 		Capacity: 2048000,
 	},
 	LowerCaseTableNames: 2,
+	ServerVersion:       "",
 	Log: Log{
 		Level:               "info",
 		Format:              "text",
@@ -643,6 +645,9 @@ func (c *Config) Load(confFile string) error {
 	if c.TokenLimit == 0 {
 		c.TokenLimit = 1000
 	}
+	if len(c.ServerVersion) > 0 {
+		mysql.ServerVersion = c.ServerVersion
+	}
 	// If any items in confFile file are not mapped into the Config struct, issue
 	// an error and stop the server from starting.
 	undecoded := metaData.Undecoded()

config/config.toml.example

@@ -74,6 +74,12 @@ split-region-max-num = 1000
 # In order to support "drop primary key" operation , this flag must be true and the table does not have the pkIsHandle flag.
 alter-primary-key = false
 
+# server-version is used to change the version string of TiDB in the following scenarios:
+# 1. the server version returned by builtin-function `VERSION()`.
+# 2. the server version filled in handshake packets of MySQL Connection Protocol, see https://dev.mysql.com/doc/internals/en/connection-phase-packets.html#packet-Protocol::Handshake for more details.
+# if server-version = "", the default value(original TiDB version string) is used.
+server-version = ""
+
 # repair mode is used to repair the broken table meta in TiKV in extreme cases.
 repair-mode = false
 

config/config_test.go

@@ -23,6 +23,7 @@ import (
 	"github.com/BurntSushi/toml"
 	. "github.com/pingcap/check"
 	zaplog "github.com/pingcap/log"
+	"github.com/pingcap/parser/mysql"
 	"github.com/pingcap/tidb/util/logutil"
 	tracing "github.com/uber/jaeger-client-go/config"
 )
@@ -179,6 +180,7 @@ alter-primary-key = true
 delay-clean-table-lock = 5
 split-region-max-num=10000
 enable-batch-dml = true
+server-version = "test_version"
 repair-mode = true
 [performance]
 txn-total-size-limit=2000
@@ -197,6 +199,8 @@ max-sql-length=1024
 
 	c.Assert(conf.Load(configFile), IsNil)
 
+	c.Assert(conf.ServerVersion, Equals, "test_version")
+	c.Assert(mysql.ServerVersion, Equals, conf.ServerVersion)
 	// Test that the original value will not be clear by load the config file that does not contain the option.
 	c.Assert(conf.Binlog.Enable, Equals, true)
 	c.Assert(conf.Binlog.Strategy, Equals, "hash")