基于Golang实现Redis协议解析器
更新时间：2023年03月24日 11:08:19 作者：CSGOPHER
这篇文章主要为大家详细介绍了如何通过GO语言编写简单的Redis协议解析器，文中的示例代码讲解详细，对我们深入了解Go语言有一定的帮助，需要的可以参考一下
本文实现Redis的协议层，协议层负责解析指令，然后将指令交给核心database执行
echo database用来测试协议层的代码
https://github.com/csgopher/go-redis
RESP协议
RESP是客户端与服务端通信的协议，格式有五种：
正常回复：以“+”开头，以“\r\n”结尾的字符串形式
错误回复：以“-”开头，以“\r\n”结尾的字符串形式
整数：以“:”开头，以“\r\n”结尾的字符串形式
多行字符串：以“$”开头，后跟实际发送字节数，再以“\r\n”开头和结尾
$3\r\nabc\r\n
数组：以“*”开头，后跟成员个数
SET key value
*3\r\n$3\r\nSET\r\n$3\r\nkey\r\n$5\r\nvalue\r\n
客户端和服务器发送的命令或数据一律以 \r\n （CRLF）作为换行符。
当我们输入*3\r\n$3\r\nSET\r\n$3\r\nkey\r\n$5\r\nvalue\r\n这样一串命令，服务端接收到的是如下的命令：
*3\r\n
$3\r\n
SET\r\n
$3\r\n
key\r\n
$5\r\n
value\r\n
interface/resp/conn.go
type Connection interface {
Write([]byte) error
GetDBIndex() int
SelectDB(int)
}
interface/resp/reply.go
type Reply interface {
ToBytes() []byte
}
- Connection接口：Redis客户端的一个连接
- Write：给客户端回复消息
- GetDBIndex：Redis有16个DB
- Reply接口：响应接口
resp/reply/consts.go
type PongReply struct{}
var pongBytes = []byte("+PONG\r\n")
func (r *PongReply) ToBytes() []byte {
return pongBytes
}
var thePongReply = new(PongReply)
func MakePongReply() *PongReply {
return thePongReply
}
type OkReply struct{}
var okBytes = []byte("+OK\r\n")
func (r *OkReply) ToBytes() []byte {
return okBytes
}
var theOkReply = new(OkReply)
func MakeOkReply() *OkReply {
return theOkReply
}
var nullBulkBytes = []byte("$-1\r\n")
type NullBulkReply struct{}
func (r *NullBulkReply) ToBytes() []byte {
return nullBulkBytes
}
func MakeNullBulkReply() *NullBulkReply {
return &NullBulkReply{}
}
var emptyMultiBulkBytes = []byte("*0\r\n")
type EmptyMultiBulkReply struct{}
func (r *EmptyMultiBulkReply) ToBytes() []byte {
return emptyMultiBulkBytes
}
type NoReply struct{}
var noBytes = []byte("")
func (r *NoReply) ToBytes() []byte {
return noBytes
}
定义五种回复：回复pong，ok，null，空数组，空
resp/reply/reply.go
type ErrorReply interface {
Error() string
ToBytes() []byte
}
ErrorReply：定义错误接口
resp/reply/errors.go
type UnknownErrReply struct{}
var unknownErrBytes = []byte("-Err unknown\r\n")
func (r *UnknownErrReply) ToBytes() []byte {
return unknownErrBytes
}
func (r *UnknownErrReply) Error() string {
return "Err unknown"
}
type ArgNumErrReply struct {
Cmd string
}
func (r *ArgNumErrReply) ToBytes() []byte {
return []byte("-ERR wrong number of arguments for '" + r.Cmd + "' command\r\n")
}
func (r *ArgNumErrReply) Error() string {
return "ERR wrong number of arguments for '" + r.Cmd + "' command"
}
func MakeArgNumErrReply(cmd string) *ArgNumErrReply {
return &ArgNumErrReply{
Cmd: cmd,
}
}
type SyntaxErrReply struct{}
var syntaxErrBytes = []byte("-Err syntax error\r\n")
var theSyntaxErrReply = &SyntaxErrReply{}
func MakeSyntaxErrReply() *SyntaxErrReply {
return theSyntaxErrReply
}
func (r *SyntaxErrReply) ToBytes() []byte {
return syntaxErrBytes
}
func (r *SyntaxErrReply) Error() string {
return "Err syntax error"
}
type WrongTypeErrReply struct{}
var wrongTypeErrBytes = []byte("-WRONGTYPE Operation against a key holding the wrong kind of value\r\n")
func (r *WrongTypeErrReply) ToBytes() []byte {
return wrongTypeErrBytes
}
func (r *WrongTypeErrReply) Error() string {
return "WRONGTYPE Operation against a key holding the wrong kind of value"
}
type ProtocolErrReply struct {
Msg string
}
func (r *ProtocolErrReply) ToBytes() []byte {
return []byte("-ERR Protocol error: '" + r.Msg + "'\r\n")
}
func (r *ProtocolErrReply) Error() string {
return "ERR Protocol error: '" + r.Msg
}
errors定义5种错误：UnknownErrReply 未知错误，ArgNumErrReply 参数个数错误，SyntaxErrReply 语法错误，WrongTypeErrReply 数据类型错误，ProtocolErrReply 协议错误
resp/reply/reply.go
var (
nullBulkReplyBytes = []byte("$-1")
// 协议的结尾
CRLF = "\r\n"
)
type BulkReply struct {
Arg []byte
}
func MakeBulkReply(arg []byte) *BulkReply {
return &BulkReply{
Arg: arg,
}
}
func (r *BulkReply) ToBytes() []byte {
if len(r.Arg) == 0 {
return nullBulkReplyBytes
}
return []byte("$" + strconv.Itoa(len(r.Arg)) + CRLF + string(r.Arg) + CRLF)
}
type MultiBulkReply struct {
Args [][]byte
}
func (r *MultiBulkReply) ToBytes() []byte {
argLen := len(r.Args)
var buf bytes.Buffer
buf.WriteString("*" + strconv.Itoa(argLen) + CRLF)
for _, arg := range r.Args {
if arg == nil {
buf.WriteString("$-1" + CRLF)
} else {
buf.WriteString("$" + strconv.Itoa(len(arg)) + CRLF + string(arg) + CRLF)
}
}
return buf.Bytes()
}
func MakeMultiBulkReply(args [][]byte) *MultiBulkReply {
return &MultiBulkReply{
Args: args,
}
}
type StatusReply struct {
Status string
}
func MakeStatusReply(status string) *StatusReply {
return &StatusReply{
Status: status,
}
}
func (r *StatusReply) ToBytes() []byte {
return []byte("+" + r.Status + CRLF)
}
type IntReply struct {
Code int64
}
func MakeIntReply(code int64) *IntReply {
return &IntReply{
Code: code,
}
}
func (r *IntReply) ToBytes() []byte {
return []byte(":" + strconv.FormatInt(r.Code, 10) + CRLF)
}
type StandardErrReply struct {
Status string
}
func (r *StandardErrReply) ToBytes() []byte {
return []byte("-" + r.Status + CRLF)
}
func (r *StandardErrReply) Error() string {
return r.Status
}
func MakeErrReply(status string) *StandardErrReply {
return &StandardErrReply{
Status: status,
}
}
func IsErrorReply(reply resp.Reply) bool {
return reply.ToBytes()[0] == '-'
}
- BulkReply：回复一个字符串
- MultiBulkReply：回复字符串数组
- StatusReply：状态回复
- IntReply：数字回复
- StandardErrReply：标准错误回复
- IsErrorReply：判断是否为错误回复
- ToBytes：将字符串转成RESP协议规定的格式
resp/parser/parser.go
type Payload struct {
Data resp.Reply
Err error
}
type readState struct {
readingMultiLine bool
expectedArgsCount int
msgType byte
args [][]byte
bulkLen int64
}
func (s *readState) finished() bool {
return s.expectedArgsCount > 0 && len(s.args) == s.expectedArgsCount
}
func ParseStream(reader io.Reader) <-chan *Payload {
ch := make(chan *Payload)
go parse0(reader, ch)
return ch
}
func parse0(reader io.Reader, ch chan<- *Payload) {
......
}
Payload结构体：客服端给我们发的数据
Reply：客户端与服务端互相发的数据都称为Reply
readState结构体：
- readingMultiLine：解析单行还是多行数据
- expectedArgsCount：应该读取的参数个数
- msgType：消息类型
- args：消息内容
- bulkLen：数据长度
finished方法：判断解析是否完成
ParseStream方法：异步解析数据后放入管道，返回管道数据
func readLine(bufReader *bufio.Reader, state *readState) ([]byte, bool, error) {
var msg []byte
var err error
if state.bulkLen == 0 {
msg, err = bufReader.ReadBytes('\n')
if err != nil {
return nil, true, err
}
if len(msg) == 0 || msg[len(msg)-2] != '\r' {
return nil, false, errors.New("protocol error: " + string(msg))
}
} else {
msg = make([]byte, state.bulkLen+2)
_, err = io.ReadFull(bufReader, msg)
if err != nil {
return nil, true, err
}
if len(msg) == 0 || msg[len(msg)-2] != '\r' || msg[len(msg)-1] != '\n' {
return nil, false, errors.New("protocol error: " + string(msg))
}
state.bulkLen = 0
}
return msg, false, nil
}
readLine：一行一行的读取。读正常的行，以\n分隔。读正文中包含\r\n字符的行时，state.bulkLen加上换行符\r\n（state.bulkLen+2）
func parseMultiBulkHeader(msg []byte, state *readState) error {
var err error
var expectedLine uint64
expectedLine, err = strconv.ParseUint(string(msg[1:len(msg)-2]), 10, 32)
if err != nil {
return errors.New("protocol error: " + string(msg))
}
if expectedLine == 0 {
state.expectedArgsCount = 0
return nil
} else if expectedLine > 0 {
state.msgType = msg[0]
state.readingMultiLine = true
state.expectedArgsCount = int(expectedLine)
state.args = make([][]byte, 0, expectedLine)
return nil
} else {
return errors.New("protocol error: " + string(msg))
}
}
func parseBulkHeader(msg []byte, state *readState) error {
var err error
state.bulkLen, err = strconv.ParseInt(string(msg[1:len(msg)-2]), 10, 64)
if err != nil {
return errors.New("protocol error: " + string(msg))
}
if state.bulkLen == -1 { // null bulk
return nil
} else if state.bulkLen > 0 {
state.msgType = msg[0]
state.readingMultiLine = true
state.expectedArgsCount = 1
state.args = make([][]byte, 0, 1)
return nil
} else {
return errors.New("protocol error: " + string(msg))
}
}
parseMultiBulkHeader：解析数组的头部，设置期望的行数和相关参数。
parseBulkHeader：解析多行字符串的头部。
func parseSingleLineReply(msg []byte) (resp.Reply, error) {
str := strings.TrimSuffix(string(msg), "\r\n")
var result resp.Reply
switch msg[0] {
case '+': // status reply
result = reply.MakeStatusReply(str[1:])
case '-': // err reply
result = reply.MakeErrReply(str[1:])
case ':': // int reply
val, err := strconv.ParseInt(str[1:], 10, 64)
if err != nil {
return nil, errors.New("protocol error: " + string(msg))
}
result = reply.MakeIntReply(val)
}
return result, nil
}
func readBody(msg []byte, state *readState) error {
line := msg[0 : len(msg)-2]
var err error
if line[0] == '$' {
// bulk reply
state.bulkLen, err = strconv.ParseInt(string(line[1:]), 10, 64)
if err != nil {
return errors.New("protocol error: " + string(msg))
}
if state.bulkLen <= 0 { // null bulk in multi bulks
state.args = append(state.args, []byte{})
state.bulkLen = 0
}
} else {
state.args = append(state.args, line)
}
return nil
}
parseSingleLineReply：解析单行命令
readBody：读取多行的命令，如果是$开头，设置bulkLen，读取下一行时根据这个+2，不是$开头则直接添加到args
func parse0(reader io.Reader, ch chan<- *Payload) {
defer func() {
if err := recover(); err != nil {
logger.Error(string(debug.Stack()))
}
}()
bufReader := bufio.NewReader(reader)
var state readState
var err error
var msg []byte
for {
var ioErr bool
msg, ioErr, err = readLine(bufReader, &state)
if err != nil {
if ioErr {
ch <- &Payload{
Err: err,
}
close(ch)
return
}
ch <- &Payload{
Err: err,
}
state = readState{}
continue
}
if !state.readingMultiLine {
if msg[0] == '*' {
// multi bulk reply
err = parseMultiBulkHeader(msg, &state)
if err != nil {
ch <- &Payload{
Err: errors.New("protocol error: " + string(msg)),
}
state = readState{}
continue
}
if state.expectedArgsCount == 0 {
ch <- &Payload{
Data: &reply.EmptyMultiBulkReply{},
}
state = readState{}
continue
}
} else if msg[0] == '$' { // bulk reply
err = parseBulkHeader(msg, &state)
if err != nil {
ch <- &Payload{
Err: errors.New("protocol error: " + string(msg)),
}
state = readState{} // reset state
continue
}
if state.bulkLen == -1 { // null bulk reply
ch <- &Payload{
Data: &reply.NullBulkReply{},
}
state = readState{} // reset state
continue
}
} else {
// single line reply
result, err := parseSingleLineReply(msg)
ch <- &Payload{
Data: result,
Err: err,
}
state = readState{} // reset state
continue
}
} else {
// read bulk reply
err = readBody(msg, &state)
if err != nil {
ch <- &Payload{
Err: errors.New("protocol error: " + string(msg)),
}
state = readState{} // reset state
continue
}
// if sending finished
if state.finished() {
var result resp.Reply
if state.msgType == '*' {
result = reply.MakeMultiBulkReply(state.args)
} else if state.msgType == '$' {
result = reply.MakeBulkReply(state.args[0])
}
ch <- &Payload{
Data: result,
Err: err,
}
state = readState{}
}
}
}
}
parse0：解析指令，解析完成后通过channel发出去
resp/connection/conn.go
type Connection struct {
conn net.Conn
waitingReply wait.Wait
mu sync.Mutex // 避免多个协程往客户端中写
selectedDB int
}
func NewConn(conn net.Conn) *Connection {
return &Connection{
conn: conn,
}
}
func (c *Connection) RemoteAddr() net.Addr {
return c.conn.RemoteAddr()
}
func (c *Connection) Close() error {
c.waitingReply.WaitWithTimeout(10 * time.Second)
_ = c.conn.Close()
return nil
}
func (c *Connection) Write(b []byte) error {
if len(b) == 0 {
return nil
}
c.mu.Lock()
c.waitingReply.Add(1)
defer func() {
c.waitingReply.Done()
c.mu.Unlock()
}()
_, err := c.conn.Write(b)
return err
}
func (c *Connection) GetDBIndex() int {
return c.selectedDB
}
func (c *Connection) SelectDB(dbNum int) {
c.selectedDB = dbNum
}
之前写的EchoHandler是用户传过来什么，我们传回去什么。现在要写一个RespHandler来代替EchoHandler，让解析器来解析。RespHandler中要有一个管理客户端连接的结构体Connection。
Connection：客户端连接，在协议层的handler中会用到
resp/handler/handler.go
var (
unknownErrReplyBytes = []byte("-ERR unknown\r\n")
)
type RespHandler struct {
activeConn sync.Map
db databaseface.Database
closing atomic.Boolean
}
func MakeHandler() *RespHandler {
var db databaseface.Database
db = database.NewEchoDatabase()
return &RespHandler{
db: db,
}
}
func (h *RespHandler) closeClient(client *connection.Connection) {
_ = client.Close()
h.db.AfterClientClose(client)
h.activeConn.Delete(client)
}
func (h *RespHandler) Handle(ctx context.Context, conn net.Conn) {
if h.closing.Get() {
// closing handler refuse new connection
_ = conn.Close()
}
client := connection.NewConn(conn)
h.activeConn.Store(client, 1)
ch := parser.ParseStream(conn)
for payload := range ch {
if payload.Err != nil {
if payload.Err == io.EOF ||
payload.Err == io.ErrUnexpectedEOF ||
strings.Contains(payload.Err.Error(), "use of closed network connection") {
// connection closed
h.closeClient(client)
logger.Info("connection closed: " + client.RemoteAddr().String())
return
}
// protocol err
errReply := reply.MakeErrReply(payload.Err.Error())
err := client.Write(errReply.ToBytes())
if err != nil {
h.closeClient(client)
logger.Info("connection closed: " + client.RemoteAddr().String())
return
}
continue
}
if payload.Data == nil {
logger.Error("empty payload")
continue
}
r, ok := payload.Data.(*reply.MultiBulkReply)
if !ok {
logger.Error("require multi bulk reply")
continue
}
result := h.db.Exec(client, r.Args)
if result != nil {
_ = client.Write(result.ToBytes())
} else {
_ = client.Write(unknownErrReplyBytes)
}
}
}
func (h *RespHandler) Close() error {
logger.Info("handler shutting down...")
h.closing.Set(true)
// TODO: concurrent wait
h.activeConn.Range(func(key interface{}, val interface{}) bool {
client := key.(*connection.Connection)
_ = client.Close()
return true
})
h.db.Close()
return nil
}
RespHandler：和之前的echo类似，加了核心层的db.exec执行解析的指令
interface/database/database.go
type CmdLine = [][]byte
type Database interface {
Exec(client resp.Connection, args [][]byte) resp.Reply
AfterClientClose(c resp.Connection)
Close()
}
type DataEntity struct {
Data interface{}
}
Exec：核心层的执行
AfterClientClose：关闭之后的善后方法
CmdLine：二维字节数组的指令别名
DataEntity：表示Redis的数据，包括string, list, set等等
database/echo_database.go
type EchoDatabase struct {
}
func NewEchoDatabase() *EchoDatabase {
return &EchoDatabase{}
}
func (e EchoDatabase) Exec(client resp.Connection, args [][]byte) resp.Reply {
return reply.MakeMultiBulkReply(args)
}
func (e EchoDatabase) AfterClientClose(c resp.Connection) {
logger.Info("EchoDatabase AfterClientClose")
}
func (e EchoDatabase) Close() {
logger.Info("EchoDatabase Close")
}
echo_database：测试协议层
Exec：指令解析后，再使用MakeMultiBulkReply包装一下返回去
main.go
err := tcp.ListenAndServeWithSignal(
&tcp.Config{
Address: fmt.Sprintf("%s:%d",
config.Properties.Bind,
config.Properties.Port),
},
handler.MakeHandler())
if err != nil {
logger.Error(err)
}
main改成刚才写的：handler.MakeHandler()
到此这篇关于基于Golang实现Redis协议解析器的文章就介绍到这了,更多相关Golang Redis协议解析器内容请搜索脚本之家以前的文章或继续浏览下面的相关文章希望大家以后多多支持脚本之家！
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