Use custom code for instrumenting method calls

config/initializers/metrics.rb

@@ -7,7 +7,6 @@ if Gitlab::Metrics.enabled?
   # ActiveSupport.
   require 'gitlab/metrics/subscribers/action_view'
   require 'gitlab/metrics/subscribers/active_record'
-  require 'gitlab/metrics/subscribers/method_call'
 
   Gitlab::Application.configure do |config|
     config.middleware.use(Gitlab::Metrics::RackMiddleware)

lib/gitlab/metrics/instrumentation.rb

@@ -9,6 +9,8 @@ module Gitlab
     #
     #     Gitlab::Metrics::Instrumentation.instrument_method(User, :by_login)
     module Instrumentation
+      SERIES = 'method_calls'
+
       # Instruments a class method.
       #
       # mod  - The module to instrument as a Module/Class.
@@ -31,19 +33,42 @@ module Gitlab
         alias_name = "_original_#{name}"
         target     = type == :instance ? mod : mod.singleton_class
 
+        if type == :instance
+          target = mod
+          label  = "#{mod.name}##{name}"
+        else
+          target = mod.singleton_class
+          label  = "#{mod.name}.#{name}"
+        end
+
         target.class_eval <<-EOF, __FILE__, __LINE__ + 1
           alias_method :#{alias_name}, :#{name}
 
           def #{name}(*args, &block)
-            ActiveSupport::Notifications
-              .instrument("#{type}_method.method_call",
-                          module: #{mod.name.inspect},
-                          name: #{name.inspect}) do
-                #{alias_name}(*args, &block)
-              end
+            trans = Gitlab::Metrics::Instrumentation.transaction
+
+            if trans
+              start    = Time.now
+              retval   = #{alias_name}(*args, &block)
+              duration = (Time.now - start) * 1000.0
+
+              trans.add_metric(Gitlab::Metrics::Instrumentation::SERIES,
+                               { duration: duration },
+                               method: #{label.inspect})
+
+              retval
+            else
+              #{alias_name}(*args, &block)
+            end
           end
         EOF
       end
+
+      # Small layer of indirection to make it easier to stub out the current
+      # transaction.
+      def self.transaction
+        Transaction.current
+      end
     end
   end
 end

lib/gitlab/metrics/subscribers/method_call.rb

-module Gitlab
-  module Metrics
-    module Subscribers
-      # Class for tracking method call timings.
-      class MethodCall < ActiveSupport::Subscriber
-        attach_to :method_call
-
-        SERIES = 'method_calls'
-
-        def instance_method(event)
-          return unless current_transaction
-
-          label = "#{event.payload[:module]}##{event.payload[:name]}"
-
-          add_metric(label, event.duration)
-        end
-
-        def class_method(event)
-          return unless current_transaction
-
-          label = "#{event.payload[:module]}.#{event.payload[:name]}"
-
-          add_metric(label, event.duration)
-        end
-
-        private
-
-        def add_metric(label, duration)
-          file, line = Metrics.last_relative_application_frame
-
-          values = { duration: duration, file: file, line: line }
-
-          current_transaction.add_metric(SERIES, values, method: label)
-        end
-
-        def current_transaction
-          Transaction.current
-        end
-      end
-    end
-  end
-end

spec/lib/gitlab/metrics/instrumentation_spec.rb

 require 'spec_helper'
 
 describe Gitlab::Metrics::Instrumentation do
+  let(:transaction) { Gitlab::Metrics::Transaction.new }
+
   before do
     @dummy = Class.new do
       def self.foo(text = 'foo')
@@ -31,9 +33,13 @@ describe Gitlab::Metrics::Instrumentation do
         expect(@dummy.foo).to eq('foo')
       end
 
-      it 'fires an ActiveSupport notification upon calling the method' do
-        expect(ActiveSupport::Notifications).to receive(:instrument).
-          with('class_method.method_call', module: 'Dummy', name: :foo)
+      it 'tracks the call duration upon calling the method' do
+        allow(Gitlab::Metrics::Instrumentation).to receive(:transaction).
+          and_return(transaction)
+
+        expect(transaction).to receive(:add_metric).
+          with(described_class::SERIES, an_instance_of(Hash),
+               method: 'Dummy.foo')
 
         @dummy.foo
       end
@@ -69,9 +75,13 @@ describe Gitlab::Metrics::Instrumentation do
         expect(@dummy.new.bar).to eq('bar')
       end
 
-      it 'fires an ActiveSupport notification upon calling the method' do
-        expect(ActiveSupport::Notifications).to receive(:instrument).
-          with('instance_method.method_call', module: 'Dummy', name: :bar)
+      it 'tracks the call duration upon calling the method' do
+        allow(Gitlab::Metrics::Instrumentation).to receive(:transaction).
+          and_return(transaction)
+
+        expect(transaction).to receive(:add_metric).
+          with(described_class::SERIES, an_instance_of(Hash),
+               method: 'Dummy#bar')
 
         @dummy.new.bar
       end

spec/lib/gitlab/metrics/subscribers/method_call_spec.rb

-require 'spec_helper'
-
-describe Gitlab::Metrics::Subscribers::MethodCall do
-  let(:transaction) { Gitlab::Metrics::Transaction.new }
-
-  let(:subscriber) { described_class.new }
-
-  let(:event) do
-    double(:event, duration: 0.2, payload: { module: 'Foo', name: :foo })
-  end
-
-  before do
-    allow(subscriber).to receive(:current_transaction).and_return(transaction)
-
-    allow(Gitlab::Metrics).to receive(:last_relative_application_frame).
-      and_return(['app/models/foo.rb', 4])
-  end
-
-  describe '#instance_method' do
-    it 'tracks the execution of an instance method' do
-      values = { duration: 0.2, file: 'app/models/foo.rb', line: 4 }
-
-      expect(transaction).to receive(:add_metric).
-        with(described_class::SERIES, values, method: 'Foo#foo')
-
-      subscriber.instance_method(event)
-    end
-  end
-
-  describe '#class_method' do
-    it 'tracks the execution of a class method' do
-      values = { duration: 0.2, file: 'app/models/foo.rb', line: 4 }
-
-      expect(transaction).to receive(:add_metric).
-        with(described_class::SERIES, values, method: 'Foo.foo')
-
-      subscriber.class_method(event)
-    end
-  end
-end