Add leaky-bucket algorithm

[jeroenvisser101]

The Leaky Bucket Algorithm seems like a more natural algorithm to throttle requests. I've integrated this in a PHP port of rack-attack and authored it as a individual plugin: jeroenvisser101/LeakyBucket. I'd love to contribute this, as Ruby code, to rack-attack. Is this something that would fit in the vision of rack-attack?

[jeroenvisser101]

(I would add this as an additional throttle, I'm not thinking about replacing the old one)

[ktheory]

That's an interesting possibility.

Do you think it's possible to implement a leaky bucket algorithm in memcached? It's not obvious to me. 😊

[jeroenvisser101]

Yes, you'd save both the capacity and the last time it was updated, you set the TTL to the maximum time it would take to leak. Then, before you update a value, you can calculate how many seconds have passed, update the number to reflect what had leaked out, and then increase the 'drops'.

[jeroenvisser101]

I'll see if I can build a PoC for this to show how it would work!

[jeroenvisser101]

Hey @ktheory, I've created a PR (and it's green 🎉), let me know if you've got any questions or remarks!