HTTP Request Rate Limiter for Rack Applications =============================================== [![Code Climate](https://codeclimate.com/badge.png)](https://codeclimate.com/github/bensomers/improved-rack-throttle) [![Dependency Status](https://gemnasium.com/bensomers/improved-rack-throttle.png)](https://gemnasium.com/bensomers/improved-rack-throttle) [![Build Status](https://travis-ci.org/bensomers/improved-rack-throttle.png?branch=master)](https://travis-ci.org/bensomers/improved-rack-throttle) This is a [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). * Scopes throttling rules by request path, http method, or user_agent for applications that need a variety of rules * 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). This makes it easy to use global counters across multiple web servers. * 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] Examples -------- ### Adding throttling to a Rails 3.x application # config/application.rb require 'rack/throttle' class Application < Rails::Application config.middleware.use Rack::Throttle::Interval end ### Adding throttling to a Sinatra application #!/usr/bin/env ruby -rubygems require 'sinatra' require 'rack/throttle' use Rack::Throttle::Interval get('/hello') { "Hello, world!\n" } ### Adding throttling to a Rackup application #!/usr/bin/env rackup 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, for the foo basic auth user use Rack::Throttle::Hourly, :max => 100, :rules => {:basic_auth => /foo/} ### 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 ### Allowing 1 request per second, with bursts of up to 5 requests use Rack::Throttle::SlidingWindow, :average => 1, :burst => 5 ### 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 ### Scoping the rate-limit to a specific path and method use Rack::Throttle::Interval, :rules => {:url => /api/, :method => :post} Throttling Strategies --------------------- `Rack::Throttle` supports four 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). * `Rack::Throttle::SlidingWindow`: Throttles the application by defining an average request rate, and a burst allowance that clients can hit (as long as they stay within the average). By default, this is 1 request per second, with bursts of up to 5 requests at a time. Users who exceed the average and who have used up their burst will have all of their requests denied until they comply with the policy. 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. Scoping Rules ------------- Rack::Throttle ships with a Rack::Throttle::Matcher base class, and three implementations. Rack::Throttle::UrlMatcher and Rack::Throttle::UserAgentMatcher allow you to pass in regular expressions for request path and user agent, while Rack::Throttle::MethodMatcher will filter by request method when passed a Symbol :get, :post, :put, or :delete. These rules are additive, so you can throttle just POST requests to your '/login' page, for example. 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 can 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} * {Rack::Throttle::SlidingWindow} * {Rack::Throttle::Matcher} * {Rack::Throttle::MethodMatcher} * {Rack::Throttle::UrlMatcher} * {Rack::Throttle::UserAgentMatcher} * {Rack::Throttle::BasicAuthMatcher} Dependencies ------------ * [Rack](http://rubygems.org/gems/rack) (>= 1.0.0) Installation ------------ The recommended installation method is via [RubyGems](http://rubygems.org/). To install the latest official release of the gem, do: % [sudo] gem install improved-rack-throttle Download -------- To get a local working copy of the development repository, do: % git clone git://github.com/bensomers/improved-rack-throttle.git Alternatively, you can download the latest development version as a tarball as follows: % wget http://github.com/bensomers/improved-rack-throttle/tarball/master Authors ------- * [Ben Somers](mailto:somers.ben@gmail.com) - * [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 Support ------- Recent work on improved-rack-throttle has been funded by Rafter, Inc.