Only instrument methods defined directly

When using instrument_methods/instrument_instance_methods we only want
to instrument methods defined directly in a class, not those included
via mixins (e.g. whatever RSpec throws in during development).

In case an externally included method _has_ to be instrumented we can
still use the regular instrument_method/instrument_instance_method
methods.

lib/gitlab/metrics/instrumentation.rb

@@ -36,7 +36,9 @@ module Gitlab
       # mod - The module to instrument.
       def self.instrument_methods(mod)
         mod.public_methods(false).each do |name|
-          instrument_method(mod, name)
+          method = mod.method(name)
+
+          instrument_method(mod, name) if method.owner == mod.singleton_class
         end
       end
 
@@ -45,7 +47,9 @@ module Gitlab
       # mod - The module to instrument.
       def self.instrument_instance_methods(mod)
         mod.public_instance_methods(false).each do |name|
-          instrument_instance_method(mod, name)
+          method = mod.instance_method(name)
+
+          instrument_instance_method(mod, name) if method.owner == mod
         end
       end
 
@@ -77,7 +81,7 @@ module Gitlab
 
             if trans
               start    = Time.now
-              retval   =
+              retval   = __send__(#{alias_name.inspect}, *args, &block)
               duration = (Time.now - start) * 1000.0
 
               trans.add_metric(Gitlab::Metrics::Instrumentation::SERIES,

spec/lib/gitlab/metrics/instrumentation_spec.rb

@@ -119,6 +119,19 @@ describe Gitlab::Metrics::Instrumentation do
 
       expect(@dummy).to respond_to(:_original_foo)
     end
+
+    it 'only instruments methods directly defined in the module' do
+      mod = Module.new do
+        def kittens
+        end
+      end
+
+      @dummy.extend(mod)
+
+      described_class.instrument_methods(@dummy)
+
+      expect(@dummy).to_not respond_to(:_original_kittens)
+    end
   end
 
   describe '.instrument_instance_methods' do
@@ -131,5 +144,18 @@ describe Gitlab::Metrics::Instrumentation do
 
       expect(@dummy.method_defined?(:_original_bar)).to eq(true)
     end
+
+    it 'only instruments methods directly defined in the module' do
+      mod = Module.new do
+        def kittens
+        end
+      end
+
+      @dummy.include(mod)
+
+      described_class.instrument_instance_methods(@dummy)
+
+      expect(@dummy.method_defined?(:_original_kittens)).to eq(false)
+    end
   end
 end