/
cmd_processor_exec.go
370 lines (348 loc) · 11.8 KB
/
cmd_processor_exec.go
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// Copyright 2023 PingCAP, Inc.
// SPDX-License-Identifier: Apache-2.0
package backend
import (
"encoding/binary"
"strings"
"github.com/go-mysql-org/go-mysql/mysql"
"github.com/pingcap/tidb/parser"
"github.com/pingcap/tiproxy/lib/util/errors"
pnet "github.com/pingcap/tiproxy/pkg/proxy/net"
"github.com/siddontang/go/hack"
"go.uber.org/zap"
)
// executeCmd forwards requests and responses between the client and the backend.
// holdRequest: should the proxy send the request to the new backend.
// err: unexpected errors or MySQL errors.
func (cp *CmdProcessor) executeCmd(request []byte, clientIO, backendIO *pnet.PacketIO, waitingRedirect bool) (holdRequest bool, err error) {
backendIO.ResetSequence()
if waitingRedirect && cp.needHoldRequest(request) {
var response []byte
if _, response, err = cp.query(backendIO, "COMMIT"); err != nil {
// If commit fails, forward the response to the client.
if pnet.IsMySQLError(err) {
if writeErr := clientIO.WritePacket(response, true); writeErr != nil {
return false, writeErr
}
}
// commit txn fails; read packet fails; write packet fails.
return false, err
}
return true, err
}
return false, cp.forwardCommand(clientIO, backendIO, request)
}
func (cp *CmdProcessor) forwardCommand(clientIO, backendIO *pnet.PacketIO, request []byte) error {
cmd := pnet.Command(request[0])
// ComChangeUser is special: we need to modify the packet before forwarding.
if cmd != pnet.ComChangeUser {
if err := backendIO.WritePacket(request, true); err != nil {
return err
}
}
switch cmd {
case pnet.ComStmtPrepare:
return cp.forwardPrepareCmd(clientIO, backendIO)
case pnet.ComStmtFetch:
return cp.forwardFetchCmd(clientIO, backendIO, request)
case pnet.ComQuery, pnet.ComStmtExecute, pnet.ComProcessInfo:
return cp.forwardQueryCmd(clientIO, backendIO, request)
case pnet.ComStmtClose:
return cp.forwardCloseCmd(request)
case pnet.ComStmtSendLongData:
return cp.forwardSendLongDataCmd(request)
case pnet.ComChangeUser:
return cp.forwardChangeUserCmd(clientIO, backendIO, request)
case pnet.ComStatistics:
return cp.forwardStatisticsCmd(clientIO, backendIO)
case pnet.ComFieldList:
return cp.forwardFieldListCmd(clientIO, backendIO, request)
case pnet.ComQuit:
return cp.forwardQuitCmd()
}
// For other commands, an OK / Error / EOF packet is expected.
response, err := forwardOnePacket(clientIO, backendIO, true)
if err != nil {
return err
}
switch response[0] {
case pnet.OKHeader.Byte():
cp.handleOKPacket(request, response)
return nil
case pnet.ErrHeader.Byte():
return cp.handleErrorPacket(response)
case pnet.EOFHeader.Byte():
if cp.capability&pnet.ClientDeprecateEOF == 0 {
cp.handleEOFPacket(request, response)
} else {
cp.handleOKPacket(request, response)
}
return nil
}
// impossible here
return errors.Errorf("unexpected response, cmd:%d resp:%d", cmd, response[0])
}
func forwardOnePacket(destIO, srcIO *pnet.PacketIO, flush bool) (data []byte, err error) {
if data, err = srcIO.ReadPacket(); err != nil {
return
}
return data, destIO.WritePacket(data, flush)
}
func (cp *CmdProcessor) forwardUntilResultEnd(clientIO, backendIO *pnet.PacketIO, request []byte) (uint16, error) {
var serverStatus uint16
err := backendIO.ForwardUntil(clientIO, func(firstByte byte, length int) (end, needData bool) {
switch {
case pnet.IsErrorPacket(firstByte):
return true, true
case cp.capability&pnet.ClientDeprecateEOF == 0:
return pnet.IsEOFPacket(firstByte, length), true
default:
return pnet.IsResultSetOKPacket(firstByte, length), true
}
}, func(response []byte) error {
switch {
case pnet.IsErrorPacket(response[0]):
if err := clientIO.Flush(); err != nil {
return err
}
return cp.handleErrorPacket(response)
case cp.capability&pnet.ClientDeprecateEOF == 0:
serverStatus = cp.handleEOFPacket(request, response)
return clientIO.Flush()
default:
serverStatus = cp.handleOKPacket(request, response)
return clientIO.Flush()
}
})
return serverStatus, err
}
func (cp *CmdProcessor) forwardPrepareCmd(clientIO, backendIO *pnet.PacketIO) error {
response, err := forwardOnePacket(clientIO, backendIO, false)
if err != nil {
return err
}
switch response[0] {
case pnet.OKHeader.Byte():
// The OK packet doesn't contain a server status.
// See https://mariadb.com/kb/en/com_stmt_prepare/
numColumns := binary.LittleEndian.Uint16(response[5:])
numParams := binary.LittleEndian.Uint16(response[7:])
expectedPackets := int(numColumns) + int(numParams)
if cp.capability&pnet.ClientDeprecateEOF == 0 {
if numColumns > 0 {
expectedPackets++
}
if numParams > 0 {
expectedPackets++
}
}
// Ignore this status because PREPARE doesn't affect status.
if expectedPackets > 0 {
i := 0
err = backendIO.ForwardUntil(clientIO, func(firstByte byte, firstPktLen int) (end, needData bool) {
i++
return i >= expectedPackets, false
}, nil)
if err != nil {
return err
}
}
return clientIO.Flush()
case pnet.ErrHeader.Byte():
if err := clientIO.Flush(); err != nil {
return err
}
return cp.handleErrorPacket(response)
}
// impossible here
return errors.Errorf("unexpected response, cmd:%d resp:%d", pnet.ComStmtPrepare, response[0])
}
func (cp *CmdProcessor) forwardFetchCmd(clientIO, backendIO *pnet.PacketIO, request []byte) error {
_, err := cp.forwardUntilResultEnd(clientIO, backendIO, request)
return err
}
func (cp *CmdProcessor) forwardFieldListCmd(clientIO, backendIO *pnet.PacketIO, request []byte) error {
_, err := cp.forwardUntilResultEnd(clientIO, backendIO, request)
return err
}
func (cp *CmdProcessor) forwardQueryCmd(clientIO, backendIO *pnet.PacketIO, request []byte) error {
for {
var serverStatus uint16
var first byte
err := backendIO.ForwardUntil(clientIO, func(firstByte byte, _ int) (end, needData bool) {
first = firstByte
switch firstByte {
case pnet.OKHeader.Byte(), pnet.ErrHeader.Byte():
return true, true
default:
return true, false
}
}, func(response []byte) error {
var err error
switch first {
case pnet.OKHeader.Byte():
serverStatus = cp.handleOKPacket(request, response)
err = clientIO.Flush()
case pnet.ErrHeader.Byte():
if err = clientIO.Flush(); err != nil {
return err
}
// Subsequent statements won't be executed even if it's a multi-statement.
return cp.handleErrorPacket(response)
case pnet.LocalInFileHeader.Byte():
serverStatus, err = cp.forwardLoadInFile(clientIO, backendIO, request)
default:
serverStatus, err = cp.forwardResultSet(clientIO, backendIO, request)
}
return err
})
if err != nil {
return err
}
// If it's not the last statement in multi-statements, continue.
if serverStatus&pnet.ServerMoreResultsExists == 0 {
break
}
}
return nil
}
func (cp *CmdProcessor) forwardLoadInFile(clientIO, backendIO *pnet.PacketIO, request []byte) (serverStatus uint16, err error) {
if err = clientIO.Flush(); err != nil {
return
}
// The client sends file data until an empty packet.
for {
var data []byte
// Do not call PacketIO.ForwardUntil. It peeks 5 bytes but there may be only 4 bytes here.
if data, err = forwardOnePacket(backendIO, clientIO, false); err != nil {
return
}
if len(data) == 0 {
if err := backendIO.Flush(); err != nil {
return 0, err
}
break
}
}
var response []byte
if response, err = forwardOnePacket(clientIO, backendIO, true); err != nil {
return
}
switch response[0] {
case pnet.OKHeader.Byte():
return cp.handleOKPacket(request, response), nil
case pnet.ErrHeader.Byte():
return serverStatus, cp.handleErrorPacket(response)
}
// impossible here
return serverStatus, errors.Errorf("unexpected response, cmd:%d resp:%d", pnet.ComQuery, response[0])
}
func (cp *CmdProcessor) forwardResultSet(clientIO, backendIO *pnet.PacketIO, request []byte) (uint16, error) {
if cp.capability&pnet.ClientDeprecateEOF == 0 {
var serverStatus uint16
// read columns
err := backendIO.ForwardUntil(clientIO, func(firstByte byte, firstPktLen int) (end, needData bool) {
return pnet.IsEOFPacket(firstByte, firstPktLen), true
}, func(response []byte) error {
serverStatus = binary.LittleEndian.Uint16(response[3:])
// If a cursor exists, only columns are sent this time. The client will then send COM_STMT_FETCH to fetch rows.
// Otherwise, columns and rows are both sent once.
if serverStatus&pnet.ServerStatusCursorExists > 0 {
serverStatus = cp.handleEOFPacket(request, response)
return clientIO.Flush()
}
return nil
})
if err != nil || serverStatus&pnet.ServerStatusCursorExists > 0 {
return serverStatus, err
}
}
// Deprecate EOF or no cursor.
return cp.forwardUntilResultEnd(clientIO, backendIO, request)
}
func (cp *CmdProcessor) forwardCloseCmd(request []byte) error {
// No packet is sent to the client for COM_STMT_CLOSE.
cp.updatePrepStmtStatus(request, 0)
return nil
}
func (cp *CmdProcessor) forwardSendLongDataCmd(request []byte) error {
// No packet is sent to the client for COM_STMT_SEND_LONG_DATA.
cp.updatePrepStmtStatus(request, 0)
return nil
}
func (cp *CmdProcessor) forwardChangeUserCmd(clientIO, backendIO *pnet.PacketIO, request []byte) error {
req, err := pnet.ParseChangeUser(request, cp.capability)
if err != nil {
cp.logger.Warn("parse COM_CHANGE_USER packet encounters error", zap.Error(err))
var warning *errors.Warning
if !errors.As(err, &warning) {
return mysql.ErrMalformPacket
}
}
// The client may use the TiProxy salt to generate the auth data instead of using the TiDB salt,
// so we need another switch-auth request to pass the TiDB salt to the client.
// See https://github.com/pingcap/tiproxy/issues/127.
req.AuthPlugin = unknownAuthPlugin
req.AuthData = nil
if err := backendIO.WritePacket(pnet.MakeChangeUser(req, cp.capability), true); err != nil {
return err
}
for {
response, err := forwardOnePacket(clientIO, backendIO, true)
if err != nil {
return err
}
switch response[0] {
case pnet.OKHeader.Byte():
cp.handleOKPacket(request, response)
return nil
case pnet.ErrHeader.Byte():
return cp.handleErrorPacket(response)
default:
// If the server sends a switch-auth request, the proxy forwards the auth data to the server.
if _, err = forwardOnePacket(backendIO, clientIO, true); err != nil {
return err
}
}
}
}
func (cp *CmdProcessor) forwardStatisticsCmd(clientIO, backendIO *pnet.PacketIO) error {
// It just sends a string.
_, err := forwardOnePacket(clientIO, backendIO, true)
return err
}
func (cp *CmdProcessor) forwardQuitCmd() error {
// No returning, just disconnect.
cp.serverStatus |= StatusQuit
return nil
}
// When the following conditions are matched, we can hold the command after redirecting:
// - The proxy has received a redirect signal.
// - The session is in a transaction and waits for it to finish.
// - The incoming statement is `BEGIN` or `START TRANSACTION`, which commits the current transaction implicitly.
// The application may always omit `COMMIT` and thus the session can never be redirected.
// We can send a `COMMIT` statement to the current backend and then forward the `BEGIN` statement to the new backend.
func (cp *CmdProcessor) needHoldRequest(request []byte) bool {
cmd, data := pnet.Command(request[0]), request[1:]
// BEGIN/START TRANSACTION statements cannot be prepared.
if cmd != pnet.ComQuery {
return false
}
// Hold request only when it's waiting for the end of the transaction.
if cp.serverStatus&StatusInTrans == 0 {
return false
}
// Opening result sets can still be fetched after COMMIT/ROLLBACK, so don't hold.
if cp.hasPendingPreparedStmts() {
return false
}
if len(data) > 0 && data[len(data)-1] == 0 {
data = data[:len(data)-1]
}
query := hack.String(data)
return isBeginStmt(query)
}
func isBeginStmt(query string) bool {
normalized := parser.Normalize(query)
return strings.HasPrefix(normalized, "begin") || strings.HasPrefix(normalized, "start transaction")
}