Rolling::Limit
A redis-backed rate limiter, using redis sorted sets.
The operations are not guaranteed to be atomic, so this will be subject to race conditions - but it should be good enough for most uses where the intent is to prevent high usage, rather than to accurately count the exact number of operations within a particular time period.
Installation
Add this line to your application's Gemfile:
gem 'rolling-limit'And then execute:
$ bundle
Or install it yourself as:
$ gem install rolling-limit
Usage
Instantiate a Rolling::Limit object and then use #remaining to determine if an operation may be performed within the specified limits.
e.g.
require 'rolling/limit'
limit = Rolling::Limit.new(redis: redis, key: "u:#{user.id}:api", max_operations: 100, timespan: 60)
if limit.remaining
perform_api_operation(user)
else
raise "Limit exceeded - try again soon"
endor
e.g
require 'rolling/limit'
limit = Rolling::Limit.new(redis: connection, key: "unique key",
max_operations: 5, timespan: 60)
limit.remaining # => 4
limit.remaining # => 3
limit.remaining # => 2
limit.remaining # => 1
limit.remaining # => 0
limit.remaining # => false
# ... 61s later
limit.remaining # => 4 # Rolling::Limit is a class that maintains a rolling limit of no more than
# <max_operations> operations for a given <key> within <timespan> seconds.
class Rolling::Limit
def initialize(redis:, key:, max_operations:, timespan:)
# Increments the counter and returns truthy (with number of remaining
# operations)
def remaining
# Resets this counter
def reset!
# Returns true if there are remaining operations, without incrementing
def remaining?Development
Run docker-compose build to build a Docker image. You can then run docker-compose run --rm app bundle exec rspec to run automated tests.
To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.
Contributing
Bug reports and pull requests are welcome on GitHub at https://github.com/livelink/rolling-limit.