retwis

Retwis is the Redis Hello World. A minimal Twitter-style social network clone written using Redis and PHP. The source code is designed to be very simple and at the same time to show different Redis data structures.

You can find a tutorial explaining step by step how the example was created in the Twitter clone tutorial of the Redis documentation.

This code was written back in 2009 when Redis was initially published, in order to expose interested developers to the Redis concepts and data types. Later, in May 2014, it was reworked in order to update it to modern Redis, since when the example was introduced Redis lacked sorted sets, hashes, and many other features.

The following is a description of the data layout.

Users

User IDs are generated sequencially via increments:

INCR next_user_id => 1000

(We'll use the example user ID 1000 in the next examples)

Users are stored into Redis hashes, the key name of the hash representing a given user is user:1000. Every hash has the following fields:

username (the username of the user)
password (password of course)
auth 9458sd893448dfd

There are additional keys for following, followers, and posts:

following:1000 (sorted set of user ids)
followers:1000 (sorted set of user ids)
posts:1000 (list of posts ids)

In order to reverse lookup the user ID from the authentication toke or username we have the following two additional keys:

The key `auths` is an hash mapping auth tokens to user IDs.
Example of field and value: 9458sd893448dfd => 1000

The key `users` is an hash mapping usernames to user IDs.
Example of field and value: antirez => 1000

Additionally we take a sorted set with usernames indexed by registration time (the score is the unix time the user joined), so that we can populate our "latest users" view. The key is called users_by_time.

Posts

Posts also have sequencial IDs, generated by incrementing the following key:

INCR next_post_id => 134

Every post is stored into an hash named post:134 with the following fields:

user_id
time
body

Timeline

Just a list of post IDs in the timeline key.