Encode connection attribute only once.

Author: methane

connection.go

@@ -27,6 +27,7 @@ type mysqlConn struct{
 affectedRowsuint64
 insertIduint64
 cfg*Config
+connector*connector
 maxAllowedPacketint
 maxWriteSizeint
 writeTimeout time.Duration

connector.go

@@ -11,11 +11,54 @@ package mysql
 import (
 "context"
 "database/sql/driver"
+"fmt"
 "net"
+"os"
+"strconv"
+"strings"
 )
 
 typeconnectorstruct{
-cfg*Config// immutable private copy.
+cfg*Config// immutable private copy.
+encodedAttributesstring// Encoded connection attributes.
+}
+
+funcencodeConnectionAttributes(textAttributesstring) string{
+connAttrsBuf:=make([]byte, 0, 251)
+
+// default connection attributes
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrClientName)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrClientNameValue)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrOS)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrOSValue)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPlatform)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPlatformValue)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPid)
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, strconv.Itoa(os.Getpid()))
+
+// user-defined connection attributes
+for_, connAttr:=rangestrings.Split(textAttributes, ","){
+attr:=strings.SplitN(connAttr, ":", 2)
+iflen(attr) !=2{
+continue
+ }
+for_, v:=rangeattr{
+connAttrsBuf=appendLengthEncodedString(connAttrsBuf, v)
+ }
+ }
+
+returnstring(connAttrsBuf)
+}
+
+funcnewConnector(cfg*Config) (*connector, error){
+encodedAttributes:=encodeConnectionAttributes(cfg.ConnectionAttributes)
+iflen(encodedAttributes) >250{
+returnnil, fmt.Errorf("connection attributes are longer than 250 bytes: %dbytes (%q)", len(encodedAttributes), cfg.ConnectionAttributes)
+ }
+return&connector{
+cfg: cfg,
+encodedAttributes: encodedAttributes,
+ }, nil
 }
 
 // Connect implements driver.Connector interface.
@@ -29,6 +72,7 @@ func (c *connector) Connect(ctx context.Context) (driver.Conn, error){
 maxWriteSize: maxPacketSize-1,
 closech: make(chanstruct{}),
 cfg: c.cfg,
+connector: c,
  }
 mc.parseTime=mc.cfg.ParseTime
 

connector_test.go

@@ -8,13 +8,16 @@ import (
 )
 
 funcTestConnectorReturnsTimeout(t*testing.T){
-connector:=&connector{&Config{
+connector, err:=newConnector(&Config{
 Net: "tcp",
 Addr: "1.1.1.1:1234",
 Timeout: 10*time.Millisecond,
- }}
+ })
+iferr!=nil{
+t.Fatal(err)
+ }
 
-_, err:=connector.Connect(context.Background())
+_, err=connector.Connect(context.Background())
 iferr==nil{
 t.Fatal("error expected")
  }

driver.go

@@ -85,8 +85,9 @@ func (d MySQLDriver) Open(dsn string) (driver.Conn, error){
 iferr!=nil{
 returnnil, err
  }
-c:=&connector{
-cfg: cfg,
+c, err:=newConnector(cfg)
+iferr!=nil{
+returnnil, err
  }
 returnc.Connect(context.Background())
 }
@@ -103,7 +104,7 @@ func NewConnector(cfg *Config) (driver.Connector, error){
 iferr:=cfg.normalize(); err!=nil{
 returnnil, err
  }
-return&connector{cfg: cfg}, nil
+returnnewConnector(cfg)
 }
 
 // OpenConnector implements driver.DriverContext.
@@ -112,7 +113,5 @@ func (d MySQLDriver) OpenConnector(dsn string) (driver.Connector, error){
 iferr!=nil{
 returnnil, err
  }
-return&connector{
-cfg: cfg,
- }, nil
+returnnewConnector(cfg)
 }

packets.go

@@ -18,9 +18,6 @@ import (
 "fmt"
 "io"
 "math"
-"os"
-"strconv"
-"strings"
 "time"
 )
 
@@ -322,31 +319,12 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 pktLen+=n+1
  }
 
-connAttrsBuf:=make([]byte, 0, 100)
-
-// default connection attributes
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrClientName)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrClientNameValue)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrOS)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrOSValue)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPlatform)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPlatformValue)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, connAttrPid)
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, strconv.Itoa(os.Getpid()))
-
-// user-defined connection attributes
-for_, connAttr:=rangestrings.Split(mc.cfg.ConnectionAttributes, ","){
-attr:=strings.Split(connAttr, ":")
-iflen(attr) !=2{
-continue
- }
-for_, v:=rangeattr{
-connAttrsBuf=appendLengthEncodedString(connAttrsBuf, v)
- }
- }
-
 // 1 byte to store length of all key-values
-pktLen+=len(connAttrsBuf) +1
+// NOTE: Actually, this is length encoded integer.
+// But we support only len(connAttrBuf) < 251 for now because takeSmallBuffer
+// doesn't support buffer size more than 4096 bytes.
+// TODO(methane): Rewrite buffer management.
+pktLen+=1+len(mc.connector.encodedAttributes)
 
 // Calculate packet length and get buffer with that size
 data, err:=mc.buf.takeSmallBuffer(pktLen+4)
@@ -425,9 +403,9 @@ func (mc *mysqlConn) writeHandshakeResponsePacket(authResp []byte, plugin string
 pos++
 
 // Connection Attributes
-data[pos] =byte(len(connAttrsBuf))
+data[pos] =byte(len(mc.connector.encodedAttributes))
 pos++
-pos+=copy(data[pos:], connAttrsBuf)
+pos+=copy(data[pos:], []byte(mc.connector.encodedAttributes))
 
 // Send Auth packet
 returnmc.writePacket(data[:pos])

packets_test.go

@@ -96,9 +96,14 @@ var _ net.Conn = new(mockConn)
 
 funcnewRWMockConn(sequenceuint8) (*mockConn, *mysqlConn){
 conn:=new(mockConn)
+connector, err:=newConnector(NewConfig())
+iferr!=nil{
+panic(err)
+ }
 mc:=&mysqlConn{
 buf: newBuffer(conn),
-cfg: NewConfig(),
+cfg: connector.cfg,
+connector: connector,
 netConn: conn,
 closech: make(chanstruct{}),
 maxAllowedPacket: defaultMaxAllowedPacket,