sliding_window.rb in improved-rack-throttle-0.8.0

- old
+ new

@@ -1,11 +1,11 @@
 module Rack; module Throttle
   ##
   # This rate limiter strategy throttles the application with
   # a sliding window (implemented as a leaky bucket). It operates
-  # on second-level resolution. It takes :burst and :average 
-  # options, which correspond to the maximum size of a traffic 
+  # on second-level resolution. It takes :burst and :average
+  # options, which correspond to the maximum size of a traffic
   # burst, and the maximum allowed average traffic level.
   class SlidingWindow < Limiter
     ##
     # @param  [#call]                    app
     # @param  [Hash{Symbol => Object}]   options
@@ -16,22 +16,22 @@
       options[:burst] ||= 5
       options[:average] ||= 1
     end
 
     ##
-    # Returns `true` if the request conforms to the 
+    # Returns `true` if the request conforms to the
     # specified :average and :burst rules
     #
     # @param  [Rack::Request] request
     # @return [Boolean]
     def allowed?(request)
       t1 = request_start_time(request)
       key = cache_key(request)
       bucket = cache_get(key) rescue nil
       bucket ||= LeakyBucket.new(options[:burst], options[:average])
       bucket.maximum, bucket.outflow = options[:burst], options[:average]
-      bucket.leak! 
+      bucket.leak!
       bucket.increment!
       allowed = !bucket.full?
       begin
         cache_set(key, bucket)
         allowed
@@ -42,10 +42,19 @@
         # This prevents the Rack application blowing up merely due to a
         # backend cache server (Memcached, Redis, etc.) being offline.
       end
     end
 
+    ##
+    # Returns the number of seconds before the client is allowed to retry an
+    # HTTP request.
+    #
+    # @return [Float]
+    def retry_after
+      @retry_after ||= (1.0 / options[:average].to_f)
+    end
+
     ###
     # LeakyBucket is an internal class used to implement the
     # SlidingWindow limiter strategy. It is a (slightly tweaked)
     # implementation of the {http://en.wikipedia.org/wiki/Leaky_bucket
     # Leaky Bucket Algorithm}.
@@ -65,10 +74,10 @@
         t = Time.now
         time = t - last_touched
         loss = (outflow * time).to_f
         if loss > 0
           @count -= loss
-          @last_touched = t 
+          @last_touched = t
         end
       end
 
       def increment!
         @count = 0 if count < 0