redis-cell

> Rate limiting is one of the most common Redis use cases. Traditionally, users implemented rate limiters using server-side Lua scripts combined with client logic. In Redis 8.8, we introduce a window counter rate limiter (by @raffertyyu, together with the Redis team). I had a look for this and it turns out it's slightly mis-described there - it's not a window counter, it's a "GCRA (Generic Cell Rate Algorithm)" - a leaky bucket algorithm. Code here: https://github.com/redis/redis/blob/unstable/src/gcra.c The code comments say it was heavily influenced by https://github.com/brandur/redis-cell by Brandur Leach. It's a neat algorithm (I just learned about it today) - it only needs to store a single integer for each rate-limited key, which is the "Theoretical Arrival Time" when the bucket would next be empty.

Ah, it turns out my former colleagues @brandur, who worked on rate limiting at Stripe for some time after the blog post was written, has a Redis rate-limiting module published here: https://github.com/brandur/redis-cell/

For my site, I use Redis in addition to PostgreSQL for these purposes: - User session storage - Asynchronous "queues" for background processing using Streams (was able to eliminate RabbitMQ from my stack when I switched to this) - Rate-limiting with a GCRA (via https://github.com/brandur/redis-cell) - Bloom filter checks, specifically for making sure people aren't using passwords in data breaches (via https://github.com/RedisBloom/RedisBloom with data from https://haveibeenpwned.com/passwords)

A more efficient (but no histogram) way would be native redis module (rust) https://github.com/brandur/redis-cell

I don’t see what’s wrong with using a scripting language to extend a data store. Regardless, Redis now has modules so that you can implement these extensions in native code instead of/as well as Lua. In fact it seems the author of the post already has done so with https://github.com/brandur/redis-cell

https://github.com/brandur/redis-cell This is fast becoming my go-to tool for any sort of rate limiting at the application level.

FYI: Redis now has a module that does rate limiting for you: https://github.com/brandur/redis-cell

Personally, modules have been the thing I wanted most in redis for years, and it's been a delightful experience working on modules for the past months. I really think it's a game changer for redis and I can't wait to see where this will take it in the coming years. Some modules that are already out there (full disclosure - I work at Redis Labs and I've developed a couple of those): * redis-cell - a rate limiter module https://github.com/brandur/redis-cell * Redis Graph - a graph DB with a subset of Cipher for querying. https://github.com/swilly22/redis-module-graph * RediSeach - fast full-text search engine with fuzzy auto-suggest. https://github.com/RedisLabsModules/RediSearch * redis-ml: Machine learning models as redis data types. https://github.com/RedisLabsModules/redis-ml * redablooms - scalable bloom filters https://github.com/Redi

Author here: this was a pretty fun side project to experiment with Redis' (relatively) new module system [1], and to help me learn Rust. It uses Rust's FFI module [2] to call into a C binary, and thanks to Rust's minimal runtime and lack of a GC, this turns out to work out very well. Its benchmarks are quite good [3]. Redis provides a fairly novel API for plugging into it in that instead of using a shared object (.so), it's only exposed as a C header file. To compensate for this in a non-C language, I have a build step that compiles a library for Rust to link against [4]. It was a pleasant surprise to find that this functionality is built right into Rust's compiler. [1] https://github.com/antirez/redis/blob/unstable/src/modules/I... [2] https://doc.rust-lang.org/book/ffi.html [3] https://gist.github.com/brandur/90698498bd543598d00df46e32b