Track the amount of times views are rendered

app/views/sherlock/transactions/_file_samples.html.haml

@@ -7,6 +7,7 @@
       %thead
         %tr
           %th= t('sherlock.time_inclusive')
+          %th= t('sherlock.count')
           %th= t('sherlock.path')
           %th
       %tbody
@@ -15,6 +16,7 @@
             %td
               = sample.duration.round(2)
               = t('sherlock.milliseconds')
+            %td= @transaction.view_counts.fetch(sample.file, 1)
             %td= sample.relative_path
             %td
               = link_to(t('sherlock.view'),

config/locales/sherlock.en.yml

@@ -34,3 +34,4 @@ en:
     query_plan: Query Plan
     events: Events
     percent: '%'
+    count: Count

lib/gitlab/sherlock/transaction.rb

@@ -2,7 +2,7 @@ module Gitlab
   module Sherlock
     class Transaction
       attr_reader :id, :type, :path, :queries, :file_samples, :started_at,
-        :finished_at
+        :finished_at, :view_counts
 
       # type - The type of transaction (e.g. "GET", "POST", etc)
       # path - The path of the transaction (e.g. the HTTP request path)
@@ -15,20 +15,19 @@ module Gitlab
         @started_at = nil
         @finished_at = nil
         @thread = Thread.current
+        @view_counts = Hash.new(0)
       end
 
       # Runs the transaction and returns the block's return value.
       def run
         @started_at = Time.now
 
-        subscriber = subscribe_to_active_record
-
-        retval = profile_lines { yield }
+        retval = with_subscriptions do
+          profile_lines { yield }
+        end
 
         @finished_at = Time.now
 
-        ActiveSupport::Notifications.unsubscribe(subscriber)
-
         retval
       end
 
@@ -81,21 +80,51 @@ module Gitlab
         retval
       end
 
+      def subscribe_to_active_record
+        ActiveSupport::Notifications.subscribe('sql.active_record') do |_, start, finish, _, data|
+          next unless same_thread?
+
+          track_query(data[:sql].strip, data[:binds], start, finish)
+        end
+      end
+
+      def subscribe_to_action_view
+        regex = /render_(template|partial)\.action_view/
+
+        ActiveSupport::Notifications.subscribe(regex) do |_, start, finish, _, data|
+          next unless same_thread?
+
+          track_view(data[:identifier])
+        end
+      end
+
       private
 
       def track_query(query, bindings, start, finish)
         @queries << Query.new_with_bindings(query, bindings, start, finish)
       end
 
-      def subscribe_to_active_record
-        ActiveSupport::Notifications.subscribe('sql.active_record') do |_, start, finish, _, data|
-          # In case somebody uses a multi-threaded server locally (e.g. Puma) we
-          # _only_ want to track queries that originate from the transaction
-          # thread.
-          next unless Thread.current == @thread
+      def track_view(path)
+        @view_counts[path] += 1
+      end
 
-          track_query(data[:sql].strip, data[:binds], start, finish)
-        end
+      def with_subscriptions
+        ar_subscriber = subscribe_to_active_record
+        av_subscriber = subscribe_to_action_view
+
+        retval = yield
+
+        ActiveSupport::Notifications.unsubscribe(ar_subscriber)
+        ActiveSupport::Notifications.unsubscribe(av_subscriber)
+
+        retval
+      end
+
+      # In case somebody uses a multi-threaded server locally (e.g. Puma) we
+      # _only_ want to track notifications that originate from the transaction
+      # thread.
+      def same_thread?
+        Thread.current == @thread
       end
     end
   end

spec/lib/gitlab/sherlock/transaction_spec.rb

@@ -53,6 +53,16 @@ describe Gitlab::Sherlock::Transaction do
     end
   end
 
+  describe '#view_counts' do
+    it 'returns a Hash' do
+      expect(transaction.view_counts).to be_an_instance_of(Hash)
+    end
+
+    it 'sets the default value of a key to 0' do
+      expect(transaction.view_counts['cats.rb']).to be_zero
+    end
+  end
+
   describe '#run' do
     it 'runs the transaction' do
       allow(transaction).to receive(:profile_lines).and_yield
@@ -162,4 +172,51 @@ describe Gitlab::Sherlock::Transaction do
       end
     end
   end
+
+  describe '#subscribe_to_active_record' do
+    let(:subscription) { transaction.subscribe_to_active_record }
+    let(:time) { Time.now }
+    let(:query_data) { { sql: 'SELECT 1', binds: [] } }
+
+    after do
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    it 'tracks executed queries' do
+      expect(transaction).to receive(:track_query).
+        with('SELECT 1', [], time, time)
+
+      subscription.publish('test', time, time, nil, query_data)
+    end
+
+    it 'only tracks queries triggered from the transaction thread' do
+      expect(transaction).to_not receive(:track_query)
+
+      Thread.new { subscription.publish('test', time, time, nil, query_data) }.
+        join
+    end
+  end
+
+  describe '#subscribe_to_action_view' do
+    let(:subscription) { transaction.subscribe_to_action_view }
+    let(:time) { Time.now }
+    let(:view_data) { { identifier: 'foo.rb' } }
+
+    after do
+      ActiveSupport::Notifications.unsubscribe(subscription)
+    end
+
+    it 'tracks rendered views' do
+      expect(transaction).to receive(:track_view).with('foo.rb')
+
+      subscription.publish('test', time, time, nil, view_data)
+    end
+
+    it 'only tracks views rendered from the transaction thread' do
+      expect(transaction).to_not receive(:track_view)
+
+      Thread.new { subscription.publish('test', time, time, nil, view_data) }.
+        join
+    end
+  end
 end