Merge pull request #492 from Shopify/resource-counting-perf

Resource counting perf

lib/liquid/block_body.rb

@@ -69,8 +69,7 @@ module Liquid
 
     def render(context)
       output = []
-      context.resource_limits[:render_length_current] = 0
-      context.resource_limits[:render_score_current] += @nodelist.length
+      context.resource_limits.render_score += @nodelist.length
 
       @nodelist.each do |token|
         # Break out if we have any unhanded interrupts.
@@ -104,12 +103,13 @@ module Liquid
 
     def render_token(token, context)
       token_output = (token.respond_to?(:render) ? token.render(context) : token)
-      context.increment_used_resources(:render_length_current, token_output)
-      if context.resource_limits_reached?
-        context.resource_limits[:reached] = true
+      token_str = token_output.is_a?(Array) ? token_output.join : token_output.to_s
+
+      context.resource_limits.render_length += token_str.length
+      if context.resource_limits.reached?
         raise MemoryError.new("Memory limits exceeded".freeze)
       end
-      token_output
+      token_str
     end
 
     def create_variable(token, options)

lib/liquid/context.rb

@@ -21,9 +21,7 @@ module Liquid
       @scopes           = [(outer_scope || {})]
       @registers        = registers
       @errors           = []
-      @resource_limits  = resource_limits || Template.default_resource_limits.dup
-      @resource_limits[:render_score_current] = 0
-      @resource_limits[:assign_score_current] = 0
+      @resource_limits  = resource_limits || ResourceLimits.new(Template.default_resource_limits)
       squash_instance_assigns_with_environments
 
       @this_stack_used = false
@@ -36,20 +34,6 @@ module Liquid
       @filters = []
     end
 
-    def increment_used_resources(key, obj)
-      @resource_limits[key] += if obj.kind_of?(String) || obj.kind_of?(Array) || obj.kind_of?(Hash)
-        obj.length
-      else
-        1
-      end
-    end
-
-    def resource_limits_reached?
-      (@resource_limits[:render_length_limit] && @resource_limits[:render_length_current] > @resource_limits[:render_length_limit]) ||
-      (@resource_limits[:render_score_limit]  && @resource_limits[:render_score_current]  > @resource_limits[:render_score_limit] ) ||
-      (@resource_limits[:assign_score_limit]  && @resource_limits[:assign_score_current]  > @resource_limits[:assign_score_limit] )
-    end
-
     def strainer
       @strainer ||= Strainer.create(self, @filters)
     end

lib/liquid/resource_limits.rb

@@ -0,0 +1,23 @@
+module Liquid
+  class ResourceLimits
+    attr_accessor :render_length, :render_score, :assign_score,
+                  :render_length_limit, :render_score_limit, :assign_score_limit
+
+    def initialize(limits)
+      @render_length_limit = limits[:render_length_limit]
+      @render_score_limit = limits[:render_score_limit]
+      @assign_score_limit = limits[:assign_score_limit]
+      reset
+    end
+
+    def reached?
+      (@render_length_limit && @render_length > @render_length_limit) ||
+      (@render_score_limit  && @render_score  > @render_score_limit ) ||
+      (@assign_score_limit  && @assign_score  > @assign_score_limit )
+    end
+
+    def reset
+      @render_length = @render_score = @assign_score = 0
+    end
+  end
+end

lib/liquid/tags/assign.rb

@@ -25,7 +25,10 @@ module Liquid
     def render(context)
       val = @from.render(context)
       context.scopes.last[@to] = val
-      context.increment_used_resources(:assign_score_current, val)
+
+      inc = val.instance_of?(String) || val.instance_of?(Array) || val.instance_of?(Hash) ? val.length : 1
+      context.resource_limits.assign_score += inc
+
       ''.freeze
     end
 

lib/liquid/tags/capture.rb

@@ -25,7 +25,7 @@ module Liquid
     def render(context)
       output = super
       context.scopes.last[@to] = output
-      context.increment_used_resources(:assign_score_current, output)
+      context.resource_limits.assign_score += output.length
       ''.freeze
     end
 

lib/liquid/template.rb

@@ -18,7 +18,9 @@ module Liquid
       :locale => I18n.new
     }
 
-    attr_accessor :root, :resource_limits
+    attr_accessor :root
+    attr_reader :resource_limits
+
     @@file_system = BlankFileSystem.new
 
     class TagRegistry
@@ -110,7 +112,7 @@ module Liquid
     end
 
     def initialize
-      @resource_limits = self.class.default_resource_limits.dup
+      @resource_limits = ResourceLimits.new(self.class.default_resource_limits)
     end
 
     # Parse source code.
@@ -203,6 +205,9 @@ module Liquid
         context.add_filters(args.pop)
       end
 
+      # Retrying a render resets resource usage
+      context.resource_limits.reset
+
       begin
         # render the nodelist.
         # for performance reasons we get an array back here. join will make a string out of it.