forked from vitessio/vitess
/
conn.go
687 lines (590 loc) · 20.7 KB
/
conn.go
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package mysqlconn
import (
"bufio"
"fmt"
"io"
"net"
"github.com/youtube/vitess/go/sqldb"
querypb "github.com/youtube/vitess/go/vt/proto/query"
)
const (
// connBufferSize is how much we buffer for reading and
// writing. It is also how much we allocate for ephemeral buffers.
connBufferSize = 16 * 1024
)
// Constants for how ephemeral buffers were used for reading / writing.
const (
// ephemeralUnused means the ephemeral buffer is not in use at this
// moment. This is the default value, and is checked so we don't
// read a packet while writing one.
ephemeralUnused = iota
// ephemeralGlobalBuffer means conn.buffer was used.
// The first four bytes contain size and sequence.
ephemeralGlobalBuffer
// ephemeralSingleBuffer means a single buffer was allocated.
// It is in c.currentEphemeralPacket. The first four bytes
// contain size and sequence.
ephemeralSingleBuffer
// ephemeralBigBuffer means a big buffer was allocated, and
// will need to be split when sending.
// The allocated buffer is in c.currentEphemeralPacket.
ephemeralBigBuffer
)
// A Getter has a Get()
type Getter interface {
Get() *querypb.VTGateCallerID
}
// Conn is a connection between a client and a server, using the MySQL
// binary protocol. It is built on top of an existing net.Conn, that
// has already been established.
//
// Use Connect on the client side to create a connection.
// Use NewListener to create a server side and listen for connections.
type Conn struct {
// conn is the underlying network connection.
// Calling Close() on the Conn will close this connection.
// If there are any ongoing reads or writes, they may get interrupted.
conn net.Conn
// ConnectionID is set:
// - at Connect() time for clients, with the value returned by
// the server.
// - at accept time for the server.
ConnectionID uint32
// Capabilities is the current set of features this connection
// is using. It is the features that are both supported by
// the client and the server, and currently in use.
// It is set during the initial handshake.
//
// It is only used for CapabilityClientDeprecateEOF.
Capabilities uint32
// CharacterSet is the character set used by the other side of the
// connection.
// It is set during the initial handshake.
// See the values in constants.go.
CharacterSet uint8
// User is the name used by the client to connect.
// It is set during the initial handshake.
User string
// UserData is custom data returned by the AuthServer module.
// It is set during the initial handshake.
UserData Getter
// SchemaName is the default database name to use. It is set
// during handshake, and by ComInitDb packets. Both client and
// servers maintain it.
SchemaName string
// ServerVersion is set during Connect with the server
// version. It is not changed afterwards. It is unused for
// server-side connections.
ServerVersion string
// StatusFlags are the status flags we will base our returned flags on.
// This is a bit field, with values documented in constants.go.
// An interesting value here would be ServerStatusAutocommit.
// It is only used by the server. These flags can be changed
// by Handler methods.
StatusFlags uint16
// ClientData is a place where an application can store any
// connection-related data. Mostly used on the server side, to
// avoid maps indexed by ConnectionID for instance.
ClientData interface{}
// Packet encoding variables.
reader *bufio.Reader
writer *bufio.Writer
sequence uint8
// Internal variables for sqldb.Conn API for stream queries.
// This is set only if a streaming query is in progress, it is
// nil if no streaming query is in progress. If the streaming
// query returned no fields, this is set to an empty array
// (but not nil).
fields []*querypb.Field
// Internal buffer for zero-allocation reads and writes. This
// uses the fact that both sides of a connection either read
// packets, or write packets, but never do both, and both
// sides know who is expected to read or write a packet next.
//
// Reading side: if the next expected packet will most likely be
// small, and we don't need to hand on to the memory after reading
// the packet, use readEphemeralPacket instead of readPacket.
// If the packet is too big, it will revert to the usual read.
// But if the packet is smaller than connBufferSize, this buffer
// will be used instead.
//
// Writing side: if the next packet to write is smaller than
// connBufferSize-4, this buffer can be used to create a
// packet. It will contain both the size and sequence header,
// and the contents of the packet.
// Call startEphemeralPacket(length) to get a buffer. If length
// is smaller or equal than connBufferSize-4, this buffer will be used.
// Otherwise memory will be allocated for it.
buffer []byte
// Keep track of how and of the buffer we allocated for an
// ephemeral packet on the write side.
// These fields are used by the startEphemeralPacket /
// writeEphemeralPacket methods.
currentEphemeralPolicy int
currentEphemeralPacket []byte
}
func newConn(conn net.Conn) *Conn {
return &Conn{
conn: conn,
reader: bufio.NewReaderSize(conn, connBufferSize),
writer: bufio.NewWriterSize(conn, connBufferSize),
sequence: 0,
buffer: make([]byte, connBufferSize),
}
}
// readPacketDirect attempts to read a packet from the socket directly.
// It needs to be used for the first handshake packet the server receives,
// so we do't buffer the SSL negotiation packet. As a shortcut, only
// packets smaller than MaxPacketSize can be read here.
func (c *Conn) readPacketDirect() ([]byte, error) {
var header [4]byte
if _, err := io.ReadFull(c.conn, header[:]); err != nil {
return nil, fmt.Errorf("io.ReadFull(header size) failed: %v", err)
}
sequence := uint8(header[3])
if sequence != c.sequence {
return nil, fmt.Errorf("invalid sequence, expected %v got %v", c.sequence, sequence)
}
c.sequence++
length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
if length <= cap(c.buffer) {
// Fast path: read into buffer, we're good.
c.buffer = c.buffer[:length]
if _, err := io.ReadFull(c.conn, c.buffer); err != nil {
return nil, fmt.Errorf("io.ReadFull(direct packet body of length %v) failed: %v", length, err)
}
return c.buffer, nil
}
// Sanity check
if length == MaxPacketSize {
return nil, fmt.Errorf("readPacketDirect doesn't support more than one packet")
}
// Slow path, revert to allocating.
data := make([]byte, length)
if _, err := io.ReadFull(c.conn, data); err != nil {
return nil, fmt.Errorf("io.ReadFull(packet body of length %v) failed: %v", length, err)
}
return data, nil
}
// readEphemeralPacket attempts to read a packet into c.buffer. Do
// not use this method if the contents of the packet needs to be kept
// after the next readEphemeralPacket. If the packet is bigger than
// connBufferSize, we revert to using the same behavior as a regular readPacket.
func (c *Conn) readEphemeralPacket() ([]byte, error) {
if c.currentEphemeralPolicy != ephemeralUnused {
panic(fmt.Errorf("readEphemeralPacket: unexpected currentEphemeralPolicy: %v", c.currentEphemeralPolicy))
}
var header [4]byte
if _, err := io.ReadFull(c.reader, header[:]); err != nil {
return nil, fmt.Errorf("io.ReadFull(header size) failed: %v", err)
}
sequence := uint8(header[3])
if sequence != c.sequence {
return nil, fmt.Errorf("invalid sequence, expected %v got %v", c.sequence, sequence)
}
c.sequence++
length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
if length == 0 {
// This can be caused by the packet after a packet of
// exactly size MaxPacketSize.
return nil, nil
}
if length <= cap(c.buffer) {
// Fast path: read into buffer, we're good.
c.buffer = c.buffer[:length]
if _, err := io.ReadFull(c.reader, c.buffer); err != nil {
return nil, fmt.Errorf("io.ReadFull(packet body of length %v) failed: %v", length, err)
}
return c.buffer, nil
}
// Slow path, revert to allocating.
data := make([]byte, length)
if _, err := io.ReadFull(c.reader, data); err != nil {
return nil, fmt.Errorf("io.ReadFull(packet body of length %v) failed: %v", length, err)
}
// This is a single packet.
if length < MaxPacketSize {
return data, nil
}
// There is more than one packet, read them all.
for {
next, err := c.readOnePacket()
if err != nil {
return nil, err
}
if len(next) == 0 {
// Again, the packet after a packet of exactly size MaxPacketSize.
break
}
data = append(data, next...)
if len(next) < MaxPacketSize {
break
}
}
return data, nil
}
// readOnePacket reads a single packet into a newly allocated buffer.
func (c *Conn) readOnePacket() ([]byte, error) {
var header [4]byte
if _, err := io.ReadFull(c.reader, header[:]); err != nil {
return nil, fmt.Errorf("io.ReadFull(header size) failed: %v", err)
}
sequence := uint8(header[3])
if sequence != c.sequence {
return nil, fmt.Errorf("invalid sequence, expected %v got %v", c.sequence, sequence)
}
c.sequence++
length := int(uint32(header[0]) | uint32(header[1])<<8 | uint32(header[2])<<16)
if length == 0 {
// This can be caused by the packet after a packet of
// exactly size MaxPacketSize.
return nil, nil
}
data := make([]byte, length)
if _, err := io.ReadFull(c.reader, data); err != nil {
return nil, fmt.Errorf("io.ReadFull(packet body of length %v) failed: %v", length, err)
}
return data, nil
}
// readPacket reads a packet from the underlying connection.
// It re-assembles packets that span more than one message.
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) readPacket() ([]byte, error) {
// Optimize for a single packet case.
data, err := c.readOnePacket()
if err != nil {
return nil, err
}
// This is a single packet.
if len(data) < MaxPacketSize {
return data, nil
}
// There is more than one packet, read them all.
for {
next, err := c.readOnePacket()
if err != nil {
return nil, err
}
if len(next) == 0 {
// Again, the packet after a packet of exactly size MaxPacketSize.
break
}
data = append(data, next...)
if len(next) < MaxPacketSize {
break
}
}
return data, nil
}
// ReadPacket reads a packet from the underlying connection.
// it is the public API version, that returns a sqldb.SQLError.
// The memory for the packet is always allocated, and it is owned by the caller
// after this function returns.
func (c *Conn) ReadPacket() ([]byte, error) {
result, err := c.readPacket()
if err != nil {
return nil, sqldb.NewSQLError(CRServerLost, SSUnknownSQLState, "%v", err)
}
return result, err
}
// writePacket writes a packet, possibly cutting it into multiple
// chunks. Note this is not very efficient, as the client probably
// has to build the []byte and that makes a memory copy.
// Try to use startEphemeralPacket/writeEphemeralPacket instead.
//
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) writePacket(data []byte) error {
index := 0
length := len(data)
for {
// Packet length is capped to MaxPacketSize.
packetLength := length
if packetLength > MaxPacketSize {
packetLength = MaxPacketSize
}
// Compute and write the header.
var header [4]byte
header[0] = byte(packetLength)
header[1] = byte(packetLength >> 8)
header[2] = byte(packetLength >> 16)
header[3] = c.sequence
if n, err := c.writer.Write(header[:]); err != nil {
return fmt.Errorf("Write(header) failed: %v", err)
} else if n != 4 {
return fmt.Errorf("Write(header) returned a short write: %v < 4", n)
}
// Write the body.
if n, err := c.writer.Write(data[index : index+packetLength]); err != nil {
return fmt.Errorf("Write(packet) failed: %v", err)
} else if n != packetLength {
return fmt.Errorf("Write(packet) returned a short write: %v < %v", n, packetLength)
}
// Update our state.
c.sequence++
length -= packetLength
if length == 0 {
if packetLength == MaxPacketSize {
// The packet we just sent had exactly
// MaxPacketSize size, we need to
// sent a zero-size packet too.
header[0] = 0
header[1] = 0
header[2] = 0
header[3] = c.sequence
if n, err := c.writer.Write(header[:]); err != nil {
return fmt.Errorf("Write(empty header) failed: %v", err)
} else if n != 4 {
return fmt.Errorf("Write(empty header) returned a short write: %v < 4", n)
}
c.sequence++
}
return nil
}
index += packetLength
}
}
func (c *Conn) startEphemeralPacket(length int) []byte {
if c.currentEphemeralPolicy != ephemeralUnused {
panic("startEphemeralPacket cannot be used while a packet is already started.")
}
// Fast path: we can reuse a single memory buffer for
// both the header and the data.
if length <= cap(c.buffer)-4 {
c.currentEphemeralPolicy = ephemeralGlobalBuffer
c.buffer = c.buffer[:length+4]
c.buffer[0] = byte(length)
c.buffer[1] = byte(length >> 8)
c.buffer[2] = byte(length >> 16)
c.buffer[3] = c.sequence
c.sequence++
return c.buffer[4:]
}
// Slower path: we can use a single buffer for both the header and the data, but it has to be allocated.
if length < MaxPacketSize {
c.currentEphemeralPolicy = ephemeralSingleBuffer
c.currentEphemeralPacket = make([]byte, length+4)
c.currentEphemeralPacket[0] = byte(length)
c.currentEphemeralPacket[1] = byte(length >> 8)
c.currentEphemeralPacket[2] = byte(length >> 16)
c.currentEphemeralPacket[3] = c.sequence
c.sequence++
return c.currentEphemeralPacket[4:]
}
// Even slower path: create a full size buffer and return it.
c.currentEphemeralPolicy = ephemeralBigBuffer
c.currentEphemeralPacket = make([]byte, length)
return c.currentEphemeralPacket
}
func (c *Conn) writeEphemeralPacket(direct bool) error {
defer func() {
c.currentEphemeralPolicy = ephemeralUnused
}()
var w io.Writer = c.writer
if direct {
w = c.conn
}
switch c.currentEphemeralPolicy {
case ephemeralUnused:
// Programming error.
panic("trying to call writeEphemeralPacket while currentEphemeralPolicy is ephemeralUnused")
case ephemeralGlobalBuffer:
// Just write c.buffer as a single buffer.
// It has both header and data.
if n, err := w.Write(c.buffer); err != nil {
return fmt.Errorf("Write(c.buffer) failed: %v", err)
} else if n != len(c.buffer) {
return fmt.Errorf("Write(c.buffer) returned a short write: %v < %v", n, len(c.buffer))
}
case ephemeralSingleBuffer:
// Write the allocated buffer as a single buffer.
// It has both header and data.
if n, err := w.Write(c.currentEphemeralPacket); err != nil {
return fmt.Errorf("Write(c.currentEphemeralPacket) failed: %v", err)
} else if n != len(c.currentEphemeralPacket) {
return fmt.Errorf("Write(c.currentEphemeralPacket) returned a short write: %v < %v", n, len(c.currentEphemeralPacket))
}
case ephemeralBigBuffer:
// This is the slower path for big data.
// With direct=true, the caller expects a flush, so we call it
// manually.
if err := c.writePacket(c.currentEphemeralPacket); err != nil {
return err
}
if direct {
return c.flush()
}
}
return nil
}
// flush flushes the written data to the socket.
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) flush() error {
if err := c.writer.Flush(); err != nil {
return fmt.Errorf("Flush() failed: %v", err)
}
return nil
}
// writeComQuit writes a Quit message for the server, to indicate we
// want to close the connection.
// Client -> Server.
// Returns sqldb.SQLError(CRServerGone) if it can't.
func (c *Conn) writeComQuit() error {
// This is a new command, need to reset the sequence.
c.sequence = 0
data := c.startEphemeralPacket(1)
data[0] = ComQuit
if err := c.writeEphemeralPacket(true); err != nil {
return sqldb.NewSQLError(CRServerGone, SSUnknownSQLState, err.Error())
}
return nil
}
// RemoteAddr returns the underlying socket RemoteAddr().
func (c *Conn) RemoteAddr() net.Addr {
return c.conn.RemoteAddr()
}
// Close closes the connection. It can be called from a different go
// routine to interrupt the current connection.
func (c *Conn) Close() {
c.conn.Close()
}
//
// Packet writing methods, for generic packets.
//
// writeOKPacket writes an OK packet, directly. Do not use this if
// there is already a packet in the buffer.
// Server -> Client.
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) writeOKPacket(affectedRows, lastInsertID uint64, flags uint16, warnings uint16) error {
length := 1 + // OKPacket
lenEncIntSize(affectedRows) +
lenEncIntSize(lastInsertID) +
2 + // flags
2 // warnings
data := c.startEphemeralPacket(length)
pos := 0
pos = writeByte(data, pos, OKPacket)
pos = writeLenEncInt(data, pos, affectedRows)
pos = writeLenEncInt(data, pos, lastInsertID)
pos = writeUint16(data, pos, flags)
pos = writeUint16(data, pos, warnings)
return c.writeEphemeralPacket(true)
}
// writeOKPacketWithEOFHeader writes an OK packet with an EOF header.
// This is used at the end of a result set if
// CapabilityClientDeprecateEOF is set.
// Server -> Client.
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) writeOKPacketWithEOFHeader(affectedRows, lastInsertID uint64, flags uint16, warnings uint16) error {
length := 1 + // EOFPacket
lenEncIntSize(affectedRows) +
lenEncIntSize(lastInsertID) +
2 + // flags
2 // warnings
data := c.startEphemeralPacket(length)
pos := 0
pos = writeByte(data, pos, EOFPacket)
pos = writeLenEncInt(data, pos, affectedRows)
pos = writeLenEncInt(data, pos, lastInsertID)
pos = writeUint16(data, pos, flags)
pos = writeUint16(data, pos, warnings)
if err := c.writeEphemeralPacket(false); err != nil {
return err
}
if err := c.flush(); err != nil {
return err
}
return nil
}
// writeErrorPacket writes an error packet.
// It writes directly to the socket, so this cannot be called after other
// packets have already been written.
// Server -> Client.
// This method returns a generic error, not a sqldb.SQLError.
func (c *Conn) writeErrorPacket(errorCode uint16, sqlState string, format string, args ...interface{}) error {
errorMessage := fmt.Sprintf(format, args...)
length := 1 + 2 + 1 + 5 + len(errorMessage)
data := c.startEphemeralPacket(length)
pos := 0
pos = writeByte(data, pos, ErrPacket)
pos = writeUint16(data, pos, errorCode)
pos = writeByte(data, pos, '#')
if sqlState == "" {
sqlState = SSUnknownSQLState
}
if len(sqlState) != 5 {
panic("sqlState has to be 5 characters long")
}
pos = writeEOFString(data, pos, sqlState)
pos = writeEOFString(data, pos, errorMessage)
if err := c.writeEphemeralPacket(true); err != nil {
return err
}
return nil
}
// writeErrorPacketFromError writes an error packet, from a regular error.
// See writeErrorPacket for other info.
func (c *Conn) writeErrorPacketFromError(err error) error {
if se, ok := err.(*sqldb.SQLError); ok {
return c.writeErrorPacket(uint16(se.Num), se.State, "%v", se.Message)
}
return c.writeErrorPacket(ERUnknownError, SSUnknownSQLState, "unknown error: %v", err)
}
// writeEOFPacket writes an EOF packet, through the buffer, and
// doesn't flush (as it is used as part of a query result).
func (c *Conn) writeEOFPacket(flags uint16, warnings uint16) error {
length := 5
data := c.startEphemeralPacket(length)
pos := 0
pos = writeByte(data, pos, EOFPacket)
pos = writeUint16(data, pos, warnings)
pos = writeUint16(data, pos, flags)
return c.writeEphemeralPacket(false)
}
//
// Packet parsing methods, for generic packets.
//
func parseOKPacket(data []byte) (uint64, uint64, uint16, uint16, error) {
// We already read the type.
pos := 1
// Affected rows.
affectedRows, pos, ok := readLenEncInt(data, pos)
if !ok {
return 0, 0, 0, 0, fmt.Errorf("invalid OK packet affectedRows: %v", data)
}
// Last Insert ID.
lastInsertID, pos, ok := readLenEncInt(data, pos)
if !ok {
return 0, 0, 0, 0, fmt.Errorf("invalid OK packet lastInsertID: %v", data)
}
// Status flags.
statusFlags, pos, ok := readUint16(data, pos)
if !ok {
return 0, 0, 0, 0, fmt.Errorf("invalid OK packet statusFlags: %v", data)
}
// Warnings.
warnings, pos, ok := readUint16(data, pos)
if !ok {
return 0, 0, 0, 0, fmt.Errorf("invalid OK packet warnings: %v", data)
}
return affectedRows, lastInsertID, statusFlags, warnings, nil
}
// parseErrorPacket parses the error packet and returns a sqldb.SQLError.
func parseErrorPacket(data []byte) error {
// We already read the type.
pos := 1
// Error code is 2 bytes.
code, pos, ok := readUint16(data, pos)
if !ok {
return sqldb.NewSQLError(CRUnknownError, SSUnknownSQLState, "invalid error packet code: %v", data)
}
// '#' marker of the SQL state is 1 byte. Ignored.
pos++
// SQL state is 5 bytes
sqlState, pos, ok := readBytes(data, pos, 5)
if !ok {
return sqldb.NewSQLError(CRUnknownError, SSUnknownSQLState, "invalid error packet sqlState: %v", data)
}
// Human readable error message is the rest.
msg := string(data[pos:])
return sqldb.NewSQLError(int(code), string(sqlState), "%v", msg)
}