HTTP Request Rate Limiter for Rack Applications =============================================== This is [Rack][] middleware that provides logic for rate-limiting incoming HTTP requests to Rack applications. You can use `Rack::Throttle` with any Ruby web framework based on Rack, including with Ruby on Rails 3.0 and with Sinatra. * Features -------- * Throttles a Rack application by enforcing a minimum time interval between subsequent HTTP requests from a particular client, as well as by defining a maximum number of allowed HTTP requests per a given time period (hourly or daily). * Compatible with any Rack application and any Rack-based framework. * Stores rate-limiting counters in any key/value store implementation that responds to `#[]`/`#[]=` (like Ruby's hashes) or to `#get`/`#set` (like memcached or Redis). * Compatible with the [gdbm][] binding included in Ruby's standard library. * Compatible with the [memcached][], [memcache-client][], [memcache][] and [redis][] gems. * Compatible with [Heroku][]'s [memcached add-on][Heroku memcache] (currently available as a free beta service). Examples -------- ### Adding throttling to a Rackup application require 'rack/throttle' use Rack::Throttle::Interval run lambda { |env| [200, {'Content-Type' => 'text/plain'}, "Hello, world!\n"] } ### Enforcing a minimum 3-second interval between requests use Rack::Throttle::Interval, :min => 3.0 ### Allowing a maximum of 100 requests per hour use Rack::Throttle::Hourly, :max => 100 ### Allowing a maximum of 1,000 requests per day use Rack::Throttle::Daily, :max => 1000 ### Combining various throttling constraints into one overall policy use Rack::Throttle::Daily, :max => 1000 # requests use Rack::Throttle::Hourly, :max => 100 # requests use Rack::Throttle::Interval, :min => 3.0 # seconds ### Storing the rate-limiting counters in a GDBM database require 'gdbm' use Rack::Throttle::Interval, :cache => GDBM.new('tmp/throttle.db') ### Storing the rate-limiting counters on a Memcached server require 'memcached' use Rack::Throttle::Interval, :cache => Memcached.new, :key_prefix => :throttle ### Storing the rate-limiting counters on a Redis server require 'redis' use Rack::Throttle::Interval, :cache => Redis.new, :key_prefix => :throttle Throttling Strategies --------------------- `Rack::Throttle` supports three built-in throttling strategies: * `Rack::Throttle::Interval`: Throttles the application by enforcing a minimum interval (by default, 1 second) between subsequent HTTP requests. * `Rack::Throttle::Hourly`: Throttles the application by defining a maximum number of allowed HTTP requests per hour (by default, 3,600 requests per 60 minutes, which works out to an average of 1 request per second). * `Rack::Throttle::Daily`: Throttles the application by defining a maximum number of allowed HTTP requests per day (by default, 86,400 requests per 24 hours, which works out to an average of 1 request per second). You can fully customize the implementation details of any of these strategies by simply subclassing one of the aforementioned default implementations. And, of course, should your application-specific requirements be significantly more complex than what we've provided for, you can also define entirely new kinds of throttling strategies by subclassing the `Rack::Throttle::Limiter` base class directly. HTTP Client Identification -------------------------- The rate-limiting counters stored and maintained by `Rack::Throttle` are keyed to unique HTTP clients. By default, HTTP clients are uniquely identified by their IP address as returned by `Rack::Request#ip`. If you wish to instead use a more granular, application-specific identifier such as a session key or a user account name, you need only subclass a throttling strategy implementation and override the `#client_identifier` method. HTTP Response Codes and Headers ------------------------------- ### 403 Forbidden (Rate Limit Exceeded) When a client exceeds their rate limit, `Rack::Throttle` by default returns a "403 Forbidden" response with an associated "Rate Limit Exceeded" message in the response body. An HTTP 403 response means that the server understood the request, but is refusing to respond to it and an accompanying message will explain why. This indicates an error on the client's part in exceeding the rate limits outlined in the acceptable use policy for the site, service, or API. ### 503 Service Unavailable (Rate Limit Exceeded) However, there exists a widespread practice of instead returning a "503 Service Unavailable" response when a client exceeds the set rate limits. This is technically dubious because it indicates an error on the server's part, which is certainly not the case with rate limiting - it was the client that committed the oops, not the server. An HTTP 503 response would be correct in situations where the server was genuinely overloaded and couldn't handle more requests, but for rate limiting an HTTP 403 response is more appropriate. Nonetheless, if you think otherwise, `Rack::Throttle` does allow you to override the returned HTTP status code by passing in a `:code => 503` option when constructing a `Rack::Throttle::Limiter` instance. Documentation ------------- * {Rack::Throttle} * {Rack::Throttle::Interval} * {Rack::Throttle::Daily} * {Rack::Throttle::Hourly} Dependencies ------------ * [Rack](http://rubygems.org/gems/rack) (>= 1.0.0) Installation ------------ The recommended installation method is via RubyGems. To install the latest official release, do: % [sudo] gem install rack-throttle Download -------- To get a local working copy of the development repository, do: % git clone git://github.com/datagraph/rack-throttle.git Alternatively, you can download the latest development version as a tarball as follows: % wget http://github.com/datagraph/rack-throttle/tarball/master Authors ------- * [Arto Bendiken](mailto:arto.bendiken@gmail.com) - * [Brendon Murphy](mailto:disposable.20.xternal@spamourmet.com>) - License ------- `Rack::Throttle` is free and unencumbered public domain software. For more information, see or the accompanying UNLICENSE file. [Rack]: http://rack.rubyforge.org/ [gdbm]: http://ruby-doc.org/stdlib/libdoc/gdbm/rdoc/classes/GDBM.html [memcached]: http://rubygems.org/gems/memcached [memcache-client]: http://rubygems.org/gems/memcache-client [memcache]: http://rubygems.org/gems/memcache [redis]: http://rubygems.org/gems/redis [Heroku]: http://heroku.com/ [Heroku memcache]: http://docs.heroku.com/memcache