golang implements redis

Redis is a high-performance key-value storage database that is very popular and is widely used in scenarios such as caching, message queues, and data storage. This article will introduce how to use Go language to implement a simple Redis database.

Redis data structure

Redis is a key-value storage database in which both keys and values ​​can be of various data types. Redis supports five basic data types:

1. String: The most basic data type of Redis. String types are binary safe, meaning they can contain any data. The maximum data length is 512 MB.
2. List (List): The list type is a doubly linked list. Each node contains a string, allowing operations such as hanging, moving, and popping at both ends of the list.
3. Set: The set type is an unordered collection that contains unique, non-repeating strings.
4. Hash table (Hash): The hash table type is an unordered hash table with string fields and corresponding values. The string fields are unique and used to store key-value pairs.
5. Ordered Set (ZSet): The ordered set type is a ranked unordered set containing unique, non-duplicate members and an ordered score associated with each member.

Among the above data types, strings, lists, hash tables and ordered sets are the most commonly used types.

Different from other databases, Redis uses a single-threaded model for performance reasons and uses a large amount of memory, requiring data to be written to disk frequently.

Redis commands

Redis commands (Commands) are messages sent by the client to the Redis server. They are usually in plain text format and use
as the delimiter between commands and parameters. symbol. Each command consists of one or more parameters, where the first parameter is the command name. Redis commands can be used to operate data in the Redis database, such as reading and writing data, creating and deleting keys, etc.

The following are examples of several commonly used commands:

1. SET: Set a key-value pair.

   set key value

2. GET: Get the value of the specified key.

   get key

3. INCR: Increase the value of the specified key by 1.

   incr key

4. DECR: Decrement the value of the specified key by 1.

   decr key

5. EXPIRE: Set the expiration time of the key.

   expire key seconds

Implementing Redis database

In order to implement Redis database, we need to create five types of data structures : Strings, lists, sets, hash tables, and sorted sets. We also need to implement the Redis server so that it can accept client commands and process them.

First, we need to define a Redis database structure, which can store all key-value pairs and contains five types of data structures:

type RedisDB struct {
   StringData map[string]string
   ListData map[string][]string
   SetData map[string]map[string]bool
   HashData map[string]map[string]string
   ZsetData map[string]map[string]float64
}

Next, we define the processing of Redis command method. We can use the switch statement to write a case statement for each command name, and then dispatch to the corresponding method based on the command name and parameters, for example:

func (r *RedisDB) ExecuteCommand(command []string) interface{} {
   switch strings.ToLower(command[0]) {
   case "get":
      return r.Get(command[1])
   case "set":
      r.Set(command[1], command[2])
      return "OK"
   case "del":
      r.Del(command[1:]...)
      return "OK"
   case "exists":
      return r.Exists(command[1])
   case "expire":
      r.Expire(command[1], command[2])
      return "OK"
   }
   return fmt.Sprintf("Error: unknown command %s", command[0])
}

We need to implement a method to handle each Redis command. For example, the following is the implementation of the GET command:

func (r *RedisDB) Get(key string) interface{} {
   result, ok := r.StringData[key]
   if !ok {
      return nil
   }
   return result
}

The implementation of the SET command is as follows:

func (r *RedisDB) Set(key, value string) {
   r.StringData[key] = value
}

The implementation of the DEL command is as follows:

func (r *RedisDB) Del(keys ...string) {
   for i := range keys {
      delete(r.StringData, keys[i]) // 删除字符串
      delete(r.ListData, keys[i])   // 删除列表
      delete(r.SetData, keys[i])    // 删除集合
      delete(r.HashData, keys[i])   // 删除哈希表
      delete(r.ZsetData, keys[i])   // 删除有序集合
   }
}

EXISTS command is as follows:

func (r *RedisDB) Exists(key string) interface{} {
   _, ok1 := r.StringData[key]
   _, ok2 := r.ListData[key]
   _, ok3 := r.SetData[key]
   _, ok4 := r.HashData[key]
   _, ok5 := r.ZsetData[key]
   if ok1 || ok2 || ok3 || ok4 || ok5 {
      return true
   }
   return false
}

Finally, we implemented a simple command parser for the Redis database, which receives commands from the client and passes them to the database's command processing method to obtain a result. The code is as follows:

func (r *RedisDB) CommandParser(conn net.Conn) {
   defer conn.Close()
   reader := bufio.NewReader(conn)
   for {
      command, err := reader.ReadString('
')
      if err != nil {
         return
      }
      command = strings.TrimRight(command, "
")
      if len(command) == 0 {
         continue
      }

      args := strings.Split(command, " ")
      result := r.ExecuteCommand(args)
      data, _ := json.Marshal(result)
      conn.Write(data)
      conn.Write([]byte("
"))
   }
}

In this way, we have implemented a simple Redis database.

Test the Redis database

We can use telnet to test the Redis database. First, run the Redis server:

redis := RedisDB{
   StringData: make(map[string]string),
   ListData: make(map[string][]string),
   SetData: make(map[string]map[string]bool),
   HashData: make(map[string]map[string]string),
   ZsetData: make(map[string]map[string]float64),
}
listener, err := net.Listen("tcp", ":6379")
if err != nil {
   log.Fatal("Unable to listen on port 6379", err)
}
for {
   conn, err := listener.Accept()
   if err != nil {
      log.Println("Error accepting connection", err)
      continue
   }
   go redis.CommandParser(conn)
}

Then, use telnet to connect to the Redis server:

telnet localhost 6379

Enter the command in telnet to test the Redis database:

set name john
OK
get name
"john"
exists name
true
expire name 60
OK
del name
OK

In this way, we Successfully implemented a simple Redis database. Of course, this is just a basic implementation, and the actual Redis database also contains many advanced features, such as publish/subscribe, Lua scripts, transactions, persistence, clustering, and more. But the simple version provided in this article is enough for you to understand the basic implementation principles of Redis.

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