my_redis

This is a pure-Python implementation of Redis (just a small subset of its features). I learn about event loops and the asyncio library here.

Redis is an in-memory key-value store, which can hold values that are not restricted to strings (lists, hashes, sets, etc.). It is efficient due to its in-memory data structures and single-threaded architecture.

Implementation

The idea is to use asyncio to provide a server that accepts client connections that can parse the wire protocol for redis. There is one RedisServerProtocol per client connection, which stores state that is scoped to the lifetime of that connection. The protocol class is handed to create_server, which is called on an event loop instance.

Event loop

Event loop 
--> wait_for_key --> queue.get() --> yield --> future
--> value for key --> queue.put() --> value unlocks future --> yield on value --> resume execution

Functionality

• GET
• SET
  • SET foo bar px 2000 sets expiry of key = foo to 2 seconds
• PUBLISH
• SUBSCRIBE
• RPUSH
• LRANGE
• LPOP
• BLPOP

  Client 1: BLPOP foo
  Client 2: BLPOP foo
  Client 3: RPUSH foo bar

  Since Client 1 and 2 are indefinitely waiting, Client 3 will send bar to whichever client has been waiting the longest.
• Server replication

TODO

• PSYNC
• RDB persistence

How to run

./run_server.sh

Then install and run redis-cli