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基于Golang实现内存数据库的示例详解

2023-03-27 09:01:14 作者：CSGOPHER

这篇文章主要为大家详细介绍了如何基于Golang实现内存数据库，文中的示例代码讲解详细，具有一定的借鉴价值，需要的小伙伴可以参考一下

GO实现内存数据库

实现Redis的database层（核心层：处理命令并返回）

https://github.com/csgopher/go-redis

本文涉及以下文件：dict：定义字典的一些方法

sync_dict：实现dict
db：分数据库
command：定义指令
ping，keys，string：指令的具体处理逻辑
database：单机版数据库

datastruct/dict/dict.go

type Consumer func(key string, val interface{}) bool

type Dict interface {
   Get(key string) (val interface{}, exists bool)
   Len() int
   Put(key string, val interface{}) (result int)
   PutIfAbsent(key string, val interface{}) (result int)
   PutIfExists(key string, val interface{}) (result int)
   Remove(key string) (result int)
   ForEach(consumer Consumer)
   Keys() []string
   RandomKeys(limit int) []string
   RandomDistinctKeys(limit int) []string
   Clear()
}

Dict接口：Redis数据结构的接口。这里我们使用sync.Map作为字典的实现，如果想用别的数据结构，换一个实现即可

Consumer：遍历字典所有的键值对，返回值是布尔，true继续遍历，false停止遍历

datastruct/dict/sync_dict.go

type SyncDict struct {
   m sync.Map
}

func MakeSyncDict() *SyncDict {
   return &SyncDict{}
}

func (dict *SyncDict) Get(key string) (val interface{}, exists bool) {
   val, ok := dict.m.Load(key)
   return val, ok
}

func (dict *SyncDict) Len() int {
   length := 0
   dict.m.Range(func(k, v interface{}) bool {
      length++
      return true
   })
   return length
}

func (dict *SyncDict) Put(key string, val interface{}) (result int) {
   _, existed := dict.m.Load(key)
   dict.m.Store(key, val)
   if existed {
      return 0
   }
   return 1
}

func (dict *SyncDict) PutIfAbsent(key string, val interface{}) (result int) {
   _, existed := dict.m.Load(key)
   if existed {
      return 0
   }
   dict.m.Store(key, val)
   return 1
}

func (dict *SyncDict) PutIfExists(key string, val interface{}) (result int) {
   _, existed := dict.m.Load(key)
   if existed {
      dict.m.Store(key, val)
      return 1
   }
   return 0
}

func (dict *SyncDict) Remove(key string) (result int) {
   _, existed := dict.m.Load(key)
   dict.m.Delete(key)
   if existed {
      return 1
   }
   return 0
}

func (dict *SyncDict) ForEach(consumer Consumer) {
   dict.m.Range(func(key, value interface{}) bool {
      consumer(key.(string), value)
      return true
   })
}

func (dict *SyncDict) Keys() []string {
   result := make([]string, dict.Len())
   i := 0
   dict.m.Range(func(key, value interface{}) bool {
      result[i] = key.(string)
      i++
      return true
   })
   return result
}

func (dict *SyncDict) RandomKeys(limit int) []string {
   result := make([]string, limit)
   for i := 0; i < limit; i++ {
      dict.m.Range(func(key, value interface{}) bool {
         result[i] = key.(string)
         return false
      })
   }
   return result
}

func (dict *SyncDict) RandomDistinctKeys(limit int) []string {
   result := make([]string, limit)
   i := 0
   dict.m.Range(func(key, value interface{}) bool {
      result[i] = key.(string)
      i++
      if i == limit {
         return false
      }
      return true
   })
   return result
}

func (dict *SyncDict) Clear() {
   *dict = *MakeSyncDict()
}

使用sync.Map实现Dict接口

database/db.go

type DB struct {
	index int
	data  dict.Dict
}

type ExecFunc func(db *DB, args [][]byte) resp.Reply

type CmdLine = [][]byte

func makeDB() *DB {
	db := &DB{
		data: dict.MakeSyncDict(),
	}
	return db
}

func (db *DB) Exec(c resp.Connection, cmdLine [][]byte) resp.Reply {
	cmdName := strings.ToLower(string(cmdLine[0]))
	cmd, ok := cmdTable[cmdName]
	if !ok {
		return reply.MakeErrReply("ERR unknown command '" + cmdName + "'")
	}
	if !validateArity(cmd.arity, cmdLine) {
		return reply.MakeArgNumErrReply(cmdName)
	}
	fun := cmd.executor
	return fun(db, cmdLine[1:]) // 把 set k v 中的set切掉
}

func validateArity(arity int, cmdArgs [][]byte) bool {
	argNum := len(cmdArgs)
	if arity >= 0 {
		return argNum == arity
	}
	return argNum >= -arity
}

func (db *DB) GetEntity(key string) (*database.DataEntity, bool) {
	raw, ok := db.data.Get(key)
	if !ok {
		return nil, false
	}
	entity, _ := raw.(*database.DataEntity)
	return entity, true
}

func (db *DB) PutEntity(key string, entity *database.DataEntity) int {
	return db.data.Put(key, entity)
}

func (db *DB) PutIfExists(key string, entity *database.DataEntity) int {
	return db.data.PutIfExists(key, entity)
}

func (db *DB) PutIfAbsent(key string, entity *database.DataEntity) int {
	return db.data.PutIfAbsent(key, entity)
}

func (db *DB) Remove(key string) {
	db.data.Remove(key)
}

func (db *DB) Removes(keys ...string) (deleted int) {
	deleted = 0
	for _, key := range keys {
		_, exists := db.data.Get(key)
		if exists {
			db.Remove(key)
			deleted++
		}
	}
	return deleted
}

func (db *DB) Flush() {
	db.data.Clear()
}

实现Redis中的分数据库

ExecFunc：所有Redis的指令都写成这样的类型

validateArity方法：

定长：set k v => arity=3；
变长：exists k1 k2 k3 ... => arity=-2，表示参数>=2个

database/command.go

var cmdTable = make(map[string]*command)

type command struct {
   executor ExecFunc
   arity    int 
}

func RegisterCommand(name string, executor ExecFunc, arity int) {
   name = strings.ToLower(name)
   cmdTable[name] = &command{
      executor: executor,
      arity:    arity,
   }
}

command：每一个command结构体都是一个指令，例如ping，keys等等

arity：参数数量
cmdTable：记录所有指令和command结构体的关系
RegisterCommand：注册指令的实现，在程序

database/ping.go

func Ping(db *DB, args [][]byte) resp.Reply {
    if len(args) == 0 {
        return &reply.PongReply{}
    } else if len(args) == 1 {
        return reply.MakeStatusReply(string(args[0]))
    } else {
        return reply.MakeErrReply("ERR wrong number of arguments for 'ping' command")
    }
}

func init() {
    RegisterCommand("ping", Ping, 1)
}

init方法：在启动程序时就会调用这个方法，用于初始化

database/keys.go

func execDel(db *DB, args [][]byte) resp.Reply {
   keys := make([]string, len(args))
   for i, v := range args {
      keys[i] = string(v)
   }

   deleted := db.Removes(keys...)
   return reply.MakeIntReply(int64(deleted))
}

func execExists(db *DB, args [][]byte) resp.Reply {
   result := int64(0)
   for _, arg := range args {
      key := string(arg)
      _, exists := db.GetEntity(key)
      if exists {
         result++
      }
   }
   return reply.MakeIntReply(result)
}

func execFlushDB(db *DB, args [][]byte) resp.Reply {
   db.Flush()
   return &reply.OkReply{}
}

func execType(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   entity, exists := db.GetEntity(key)
   if !exists {
      return reply.MakeStatusReply("none")
   }
   switch entity.Data.(type) {
   case []byte:
      return reply.MakeStatusReply("string")
   }
   return &reply.UnknownErrReply{}
}

func execRename(db *DB, args [][]byte) resp.Reply {
   if len(args) != 2 {
      return reply.MakeErrReply("ERR wrong number of arguments for 'rename' command")
   }
   src := string(args[0])
   dest := string(args[1])
   
   entity, ok := db.GetEntity(src)
   if !ok {
      return reply.MakeErrReply("no such key")
   }
   db.PutEntity(dest, entity)
   db.Remove(src)
   return &reply.OkReply{}
}

func execRenameNx(db *DB, args [][]byte) resp.Reply {
   src := string(args[0])
   dest := string(args[1])

   _, exist := db.GetEntity(dest)
   if exist {
      return reply.MakeIntReply(0)
   }

   entity, ok := db.GetEntity(src)
   if !ok {
      return reply.MakeErrReply("no such key")
   }
   db.Removes(src, dest)
   db.PutEntity(dest, entity)
   return reply.MakeIntReply(1)
}

func execKeys(db *DB, args [][]byte) resp.Reply {
   pattern := wildcard.CompilePattern(string(args[0]))
   result := make([][]byte, 0)
   db.data.ForEach(func(key string, val interface{}) bool {
      if pattern.IsMatch(key) {
         result = append(result, []byte(key))
      }
      return true
   })
   return reply.MakeMultiBulkReply(result)
}

func init() {
   RegisterCommand("Del", execDel, -2)
   RegisterCommand("Exists", execExists, -2)
   RegisterCommand("Keys", execKeys, 2)
   RegisterCommand("FlushDB", execFlushDB, -1)
   RegisterCommand("Type", execType, 2)
   RegisterCommand("Rename", execRename, 3)
   RegisterCommand("RenameNx", execRenameNx, 3)
}

keys.go实现以下指令：

execDel：del k1 k2 k3 ...
execExists：exist k1 k2 k3 ...
execFlushDB：flushdb
execType：type k1
execRename：rename k1 k2
execRenameNx：renamenx k1 k2
execKeys：keys（依赖lib包的工具类wildcard.go）

database/string.go

func execGet(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   bytes, err := db.getAsString(key)
   if err != nil {
      return err
   }
   if bytes == nil {
      return &reply.NullBulkReply{}
   }
   return reply.MakeBulkReply(bytes)
}

func (db *DB) getAsString(key string) ([]byte, reply.ErrorReply) {
   entity, ok := db.GetEntity(key)
   if !ok {
      return nil, nil
   }
   bytes, ok := entity.Data.([]byte)
   if !ok {
      return nil, &reply.WrongTypeErrReply{}
   }
   return bytes, nil
}

func execSet(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   value := args[1]
   entity := &database.DataEntity{
      Data: value,
   }
   db.PutEntity(key, entity)
   return &reply.OkReply{}
}

func execSetNX(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   value := args[1]
   entity := &database.DataEntity{
      Data: value,
   }
   result := db.PutIfAbsent(key, entity)
   return reply.MakeIntReply(int64(result))
}

func execGetSet(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   value := args[1]

   entity, exists := db.GetEntity(key)
   db.PutEntity(key, &database.DataEntity{Data: value})
   if !exists {
      return reply.MakeNullBulkReply()
   }
   old := entity.Data.([]byte)
   return reply.MakeBulkReply(old)
}

func execStrLen(db *DB, args [][]byte) resp.Reply {
   key := string(args[0])
   entity, exists := db.GetEntity(key)
   if !exists {
      return reply.MakeNullBulkReply()
   }
   old := entity.Data.([]byte)
   return reply.MakeIntReply(int64(len(old)))
}

func init() {
   RegisterCommand("Get", execGet, 2)
   RegisterCommand("Set", execSet, -3)
   RegisterCommand("SetNx", execSetNX, 3)
   RegisterCommand("GetSet", execGetSet, 3)
   RegisterCommand("StrLen", execStrLen, 2)
}

string.go实现以下指令：

execGet：get k1
execSet：set k v
execSetNX：setnex k v
execGetSet：getset k v 返回旧值
execStrLen：strlen k

database/database.go

type Database struct {
   dbSet []*DB
}

func NewDatabase() *Database {
   mdb := &Database{}
   if config.Properties.Databases == 0 {
      config.Properties.Databases = 16
   }
   mdb.dbSet = make([]*DB, config.Properties.Databases)
   for i := range mdb.dbSet {
      singleDB := makeDB()
      singleDB.index = i
      mdb.dbSet[i] = singleDB
   }
   return mdb
}

func (mdb *Database) Exec(c resp.Connection, cmdLine [][]byte) (result resp.Reply) {
   defer func() {
      if err := recover(); err != nil {
         logger.Warn(fmt.Sprintf("error occurs: %v\n%s", err, string(debug.Stack())))
      }
   }()

   cmdName := strings.ToLower(string(cmdLine[0]))
   if cmdName == "select" {
      if len(cmdLine) != 2 {
         return reply.MakeArgNumErrReply("select")
      }
      return execSelect(c, mdb, cmdLine[1:])
   }
   dbIndex := c.GetDBIndex()
   selectedDB := mdb.dbSet[dbIndex]
   return selectedDB.Exec(c, cmdLine)
}

func execSelect(c resp.Connection, mdb *Database, args [][]byte) resp.Reply {
   dbIndex, err := strconv.Atoi(string(args[0]))
   if err != nil {
      return reply.MakeErrReply("ERR invalid DB index")
   }
   if dbIndex >= len(mdb.dbSet) {
      return reply.MakeErrReply("ERR DB index is out of range")
   }
   c.SelectDB(dbIndex)
   return reply.MakeOkReply()
}

func (mdb *Database) Close() {
}

func (mdb *Database) AfterClientClose(c resp.Connection) {
}

Database：一组db的集合
Exec：执行切换db指令或者其他指令
execSelect方法：选择db（指令：select 2）

resp/handler/handler.go

import (
	database2 "go-redis/database"
)

func MakeHandler() *RespHandler {
   var db database.Database
   db = database2.NewDatabase()
   return &RespHandler{
      db: db,
   }
}

修改实现协议层handler的database实现

架构小结

TCP层服务TCP的连接，然后将连接交给RESP协议层的handler，handler监听客户端的连接，将指令解析后发给管道，管道转给database层（database/database.go），核心层根据命令类型执行不同的方法，然后返回。

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