Add an reader for the epoch_time variable in the cache so that it can also be returned in the data from the throttle.

This is allows access to the same time that the cache uses for the count. This can be important for clients that want to provide rate limit information for well-behaved clients

README.md

@@ -254,13 +254,13 @@ Here's an example response that includes conventional `X-RateLimit-*` headers:
 
 ```ruby
 Rack::Attack.throttled_response = lambda do |env|
-  now = Time.now
   match_data = env['rack.attack.match_data']
+  now = match_data[:epoch_time]
 
   headers = {
     'X-RateLimit-Limit' => match_data[:limit].to_s,
     'X-RateLimit-Remaining' => '0',
-    'X-RateLimit-Reset' => (now + (match_data[:period] - now.to_i % match_data[:period])).to_s
+    'X-RateLimit-Reset' => (now + (match_data[:period] - now % match_data[:period])).to_s
   }
 
   [ 429, headers, ["Throttled\n"]]
@@ -271,7 +271,7 @@ end
 For responses that did not exceed a throttle limit, Rack::Attack annotates the env with match data:
 
 ```ruby
-request.env['rack.attack.throttle_data'][name] # => { :count => n, :period => p, :limit => l }
+request.env['rack.attack.throttle_data'][name] # => { :count => n, :period => p, :limit => l, :epoch_time => t }
 ```
 
 ## Logging & Instrumentation

lib/rack/attack/cache.rb

@@ -3,6 +3,7 @@ module Rack
     class Cache
 
       attr_accessor :prefix
+      attr_reader :last_epoch_time
 
       def initialize
         self.store = ::Rails.cache if defined?(::Rails.cache)
@@ -39,10 +40,10 @@ module Rack
       private
 
       def key_and_expiry(unprefixed_key, period)
-        epoch_time = Time.now.to_i
+        @last_epoch_time = Time.now.to_i
         # Add 1 to expires_in to avoid timing error: http://git.io/i1PHXA
-        expires_in = (period - (epoch_time % period) + 1).to_i
-        ["#{prefix}:#{(epoch_time / period).to_i}:#{unprefixed_key}", expires_in]
+        expires_in = (period - (@last_epoch_time % period) + 1).to_i
+        ["#{prefix}:#{(@last_epoch_time / period).to_i}:#{unprefixed_key}", expires_in]
       end
 
       def do_count(key, expires_in)

lib/rack/attack/throttle.rb

@@ -26,12 +26,15 @@ module Rack
         current_limit  = limit.respond_to?(:call) ? limit.call(req) : limit
         key            = "#{name}:#{discriminator}"
         count          = cache.count(key, current_period)
+        epoch_time     = cache.last_epoch_time
 
         data = {
           :count => count,
           :period => current_period,
-          :limit => current_limit
+          :limit => current_limit,
+          :epoch_time => epoch_time
         }
+
         (req.env['rack.attack.throttle_data'] ||= {})[name] = data
 
         (count > current_limit).tap do |throttled|

spec/rack_attack_throttle_spec.rb

@@ -20,7 +20,7 @@ describe 'Rack::Attack.throttle' do
     end
 
     it 'should populate throttle data' do
-      data = { :count => 1, :limit => 1, :period => @period }
+      data = { :count => 1, :limit => 1, :period => @period, epoch_time: Rack::Attack.cache.last_epoch_time.to_i }
       last_request.env['rack.attack.throttle_data']['ip/sec'].must_equal data
     end
   end
@@ -37,7 +37,7 @@ describe 'Rack::Attack.throttle' do
     it 'should tag the env' do
       last_request.env['rack.attack.matched'].must_equal 'ip/sec'
       last_request.env['rack.attack.match_type'].must_equal :throttle
-      last_request.env['rack.attack.match_data'].must_equal({:count => 2, :limit => 1, :period => @period})
+      last_request.env['rack.attack.match_data'].must_equal({:count => 2, :limit => 1, :period => @period, epoch_time: Rack::Attack.cache.last_epoch_time.to_i})
       last_request.env['rack.attack.match_discriminator'].must_equal('1.2.3.4')
     end
 
@@ -65,7 +65,7 @@ describe 'Rack::Attack.throttle with limit as proc' do
     end
 
     it 'should populate throttle data' do
-      data = { :count => 1, :limit => 1, :period => @period }
+      data = { :count => 1, :limit => 1, :period => @period, epoch_time: Rack::Attack.cache.last_epoch_time.to_i }
       last_request.env['rack.attack.throttle_data']['ip/sec'].must_equal data
     end
   end
@@ -89,7 +89,7 @@ describe 'Rack::Attack.throttle with period as proc' do
     end
 
     it 'should populate throttle data' do
-      data = { :count => 1, :limit => 1, :period => @period }
+      data = { :count => 1, :limit => 1, :period => @period, epoch_time: Rack::Attack.cache.last_epoch_time.to_i }
       last_request.env['rack.attack.throttle_data']['ip/sec'].must_equal data
     end
   end