Miniature Redis server

This is for me to learn concepts like TCP, RESP and understand redis better. I used the blog Write your own miniature Redis with Python on charlesleifer.com

Uses RESP Protocol (Redis Serialization protocol)

Data Type	Prefix	Structure	Example
Simple String	+	+{string data}\r\n	+this is a simple string\r\n
Error	-	-{error message}\r\n	-ERR unknown command "FLUHS"\r\n
Integer	:	:{the number}\r\n	:1337\r\n
Binary	$	${number of bytes}\r\n{data}\r\n	$6\r\nfoobar\r\n
Array	*	*{number of elements}\r\n{0 or more of above}\r\n	*3\r\n+a simple string element\r\n:12345\r\n$7\r\ntesting\r\n
Dictionary	%	%{number of keys}\r\n{0 or more of above}\r\n	%3\r\n+key1\r\n+value1\r\n+key2\r\n*2\r\n+value2-0\r\n+value2-1\r\n:3\r\n$7\r\ntesting\r\n
NULL	$	$-1\r\n (string of length -1)	$-1\r\n

TCP

Client → SYN → Server ("I want to connect") - SYN = Synchronize Client ← SYN-ACK ← Server ("OK, I acknowledge") - SYN-ACK = SYN(its own sequence number), ACK (acknowledges client’s number) Client → ACK → Server ("Great, we're connected") - ACK confirming server’s sequence number

gevent

Normally each connection would need its own thread. Gevent uses green threads (lightweight coroutines) instead, so 64 clients can be handled concurrently without the overhead of 64 real OS threads.

socket

A socket is basically just a door that lets two programs talk to each other over a network AF_INET just means "use the internet (IPv4)" SOCK_STREAM means "keep the line open continuously" (as opposed to sending one-off messages)

Without sockets, two programs have no way of talking to each other at all. It's the most fundamental building block of all network communication

Run

• terminal 1 python skeleton.py

• terminal 2 python

interact with the server:

from skeleton import Client

c = Client()

c.set('name', 'Alice')       # returns 1
c.get('name')                # returns 'Alice'
c.delete('name')             # returns 1
c.get('name')                # returns None

c.mset('a', '1', 'b', '2')  # set multiple keys at once
c.mget('a', 'b')             # returns ['1', '2']

c.flush()                    # clears all keys, returns count of deleted keys