Ever wonder how Redis maintains its simplicity and efficiency over the network?
Redis (Remote Dictionary Server) is a widely used in-memory data structure store that can be used as a database, cache, and message broker. One of the key aspects of Redis's efficiency and speed is its communication protocol, RESP (REdis Serialization Protocol).
This RESP helps the Redis client to communicate with the Redis server. This protocol was designed specifically for Redis, but you can use it in any client-server project.
RESP can serialize different data types including integers, strings, and arrays. It also features an error-specific type. A client sends a request to the Redis server as an array of strings.
RESP versions
- As every protocol we have versions for RESP. Here are some of them.
- Redis 2.0 supports RESP2 which become the standard
- Redis 2 - Redis 7 supports RESP2 and RESP3
RESP Magic
We have many data types that RESP supports. Let's look into some of them
Each of the data types has SET and GET commands for more inside you can look in the Redis Docs.
- Simple String: Simple strings are encoded with a
+prefix followed by the string and terminated with\r\n.
+OK\r\n
- Errors: Errors are similar to simple strings but start with
-prefix
-Error message\r\n
- Integers: Integers are encoded with a
:prefix followed by the integer and terminated with\r\n.
:1000\r\n
- Arrays: Arrays are used to transmit multiple RESP types. They start with a
*prefix followed by the number of elements in the array, a\r\n, and then the actual elements in RESP format.
*2\r\n$3\r\nfoo\r\n$3\r\nbar\r\n
If you notice each of the elements are separated by \r\n
Communication Process
When a client sends a command to the Redis server, it uses the RESP protocol to format the command. The server parses the RESP message, executes the command, and sends a RESP-formatted response back to the client.
Example
Let's consider a simple GET command:
*2\r\n$3\r\nGET\r\n$3\r\nkey\r\n
Server response (if the key exists):
$5\r\nvalue\r\n
Server response (if the key does not exist):
$-1\r\n
Each of these is translated so that it is readable by removing the \r\n.
One example with a data type
Hashes
This is the most used data type, Hashes are maps between string fields and string values, which are perfect for representing objects.
*4\r\n$4\r\nHSET\r\n$6\r\nmyhash\r\n$4\r\nname\r\n$5\r\nAlice\r\n
Server response
:1\r\n
Getting hash field
Client request:
*3\r\n$4\r\nHGET\r\n$6\r\nmyhash\r\n$4\r\nname\r\n
Server response:
$5\r\nAlice\r\n
Conclusion
RESP plays a crucial role in Redis's performance and efficiency, providing a simple yet powerful way to encode and decode messages between clients and servers. Understanding RESP and how it handles different Redis data types can help you make the most of Redis in your applications. Whether you're dealing with strings, lists, hashes, or sets, RESP ensures that communication is fast, reliable, and easy to work with.
What we learned
- How does the RESP help us serialize Redis command over the network and help us achieve the performance?
Wanna know more about RESP more
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