A Lua script extension for Redis that provides smooth, configurable, space-efficient & blazing fast rate limiting.

Configuration

Example

key = "api-access"                                                                                 
value = {"1000", "3600", "300"}                                                                    

Each actor will be rate limited to 1000 api-access events per 3600 seconds. Once the limit
is reached, the actor will be locked out for 300 seconds. Note that the rate limit applies over
a rolling window.

Features

This rate-limiting solution -

1. Does not use buckets & does not enumerate events. So it is space-efficient. It stores everything
   in a three-tuple for each actor,event pair.
2. Uses a simple linear decay function to compute available quota. So it is blazing fast.
3. Can be easily configured to rate limit over a few seconds or a few hours or a few days.

Usage

1. To check available quota without registering an event.
evalsha <SHA> 2 api-access <actor-id> <current-timestamp-seconds-since-epoch>                      

2. To check available quota while registering an event.
evalsha <SHA> 2 api-access <actor-id> <current-timestamp-seconds-since-epoch> 1                      

Included test.sh provides an example of how to configure an event type. It also shows the rate limiting in action.

The script returns available quota as a fraction. So when the rate limit is reached, it returns "0".

Performance

Processor: Intel® Core™ i7-8550U CPU @ 1.80GHz × 8
Using: benchmark.sh
Results: 142836.73 requests per second with 99% of them being served in under 0.6 ms
Note that client and server were running on the same machine. Even so, it proves that performance of this Lua script should not be an issue.