Metric name lambdas

README.md

@@ -136,6 +136,14 @@ AWS::S3::Base.singleton_class.extend StatsD::Instrument
 AWS::S3::Base.singleton_class.statsd_measure :request, 'S3.request'
 ```
 
+### Lambda As Metric Name
+
+Send a lambda instead of a string as the metric name to dynamically set the name of the metric. Useful when measuring sub classes.
+
+``` ruby
+GoogleBase.statsd_count :insert, lamdba{|object| object.class.to_s.downcase + ".insert" }
+```
+
 ## Reliance on DNS
 Out of the box StatsD is set up to be unidirectional fire-and-forget over UDP. Configuring the StatsD host to be a non-ip will trigger a DNS lookup (ie synchronous round trip network call) for each metric sent. This can be particularly problematic in clouds that have a shared DNS infrastructure such as AWS.
 

lib/statsd/instrument.rb

@@ -30,7 +30,7 @@ module Instrument
     def statsd_measure(method, name, sample_rate = StatsD.default_sample_rate)
       add_to_method(method, name, :measure) do |old_method, new_method, metric_name, *args|
         define_method(new_method) do |*args, &block|
-          StatsD.measure(metric_name, nil, sample_rate) { send(old_method, *args, &block) }
+          StatsD.measure(metric_name.respond_to?(:call) ? metric_name.call(self) : metric_name, nil, sample_rate) { send(old_method, *args, &block) }
         end
       end
     end
@@ -47,7 +47,7 @@ def statsd_count_success(method, name, sample_rate = StatsD.default_sample_rate)
             truthiness = (yield(result) rescue false) if block_given?
             result
           ensure
-            StatsD.increment("#{metric_name}." + (truthiness == false ? 'failure' : 'success'), sample_rate)
+            StatsD.increment("#{metric_name.respond_to?(:call) ? metric_name.call(self) : metric_name}." + (truthiness == false ? 'failure' : 'success'), sample_rate)
           end
         end
       end
@@ -65,7 +65,7 @@ def statsd_count_if(method, name, sample_rate = StatsD.default_sample_rate)
             truthiness = (yield(result) rescue false) if block_given?
             result
           ensure
-            StatsD.increment(metric_name, sample_rate) if truthiness
+            StatsD.increment((metric_name.respond_to?(:call) ? metric_name.call(self) : metric_name), sample_rate) if truthiness
           end
         end
       end
@@ -74,7 +74,7 @@ def statsd_count_if(method, name, sample_rate = StatsD.default_sample_rate)
     def statsd_count(method, name, sample_rate = StatsD.default_sample_rate)
       add_to_method(method, name, :count) do |old_method, new_method, metric_name|
         define_method(new_method) do |*args, &block|
-          StatsD.increment(metric_name, sample_rate)
+          StatsD.increment((metric_name.respond_to?(:call) ? metric_name.call(self) : metric_name), sample_rate)
           send(old_method, *args, &block)
         end
       end

test/statsd-instrument_test.rb

@@ -53,6 +53,9 @@ def purchase(arg)
   end
 end
 
+class GatewaySubClass < ActiveMerchant::Gateway
+end
+
 ActiveMerchant::Base.extend StatsD::Instrument
 
 class StatsDTest < Test::Unit::TestCase
@@ -128,6 +131,13 @@ def test_statsd_count
     ActiveMerchant::Gateway.new.purchase(true)
   end
 
+  def test_statsd_count_with_name_as_lambda
+    ActiveMerchant::Gateway.statsd_count(:ssl_post, lambda {|object| object.class.to_s.downcase + ".insert"})
+
+    StatsD.expects(:increment).with('gatewaysubclass.insert', StatsD.default_sample_rate)
+    GatewaySubClass.new.purchase(true)
+  end
+
   def test_statsd_count_with_method_receiving_block
     ActiveMerchant::Base.statsd_count :post_with_block, 'ActiveMerchant.Base.post_with_block'