1 files changed, 136 insertions, 0 deletions
diff --git a/lib/gitlab/sherlock/transaction.rb b/lib/gitlab/sherlock/transaction.rb
new file mode 100644
index 00000000000..3489fb251b6
--- /dev/null
+++ b/lib/gitlab/sherlock/transaction.rb
@@ -0,0 +1,136 @@
+module Gitlab
+  module Sherlock
+    class Transaction
+      attr_reader :id, :type, :path, :queries, :file_samples, :started_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)
+      def initialize(type, path)
+        @id = SecureRandom.uuid
+        @type = type
+        @path = path
+        @queries = []
+        @file_samples = []
+        @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
+
+        retval = with_subscriptions do
+          profile_lines { yield }
+        end
+
+        @finished_at = Time.now
+
+        retval
+      end
+
+      # Returns the duration in seconds.
+      def duration
+        @duration ||= started_at && finished_at ? finished_at - started_at : 0
+      end
+
+      # Returns the total query duration in seconds.
+      def query_duration
+        @query_duration ||= @queries.map { |q| q.duration }.inject(:+) / 1000.0
+      end
+
+      def to_param
+        @id
+      end
+
+      # Returns the queries sorted in descending order by their durations.
+      def sorted_queries
+        @queries.sort { |a, b| b.duration <=> a.duration }
+      end
+
+      # Returns the file samples sorted in descending order by their durations.
+      def sorted_file_samples
+        @file_samples.sort { |a, b| b.duration <=> a.duration }
+      end
+
+      # Finds a query by the given ID.
+      #
+      # id - The query ID as a String.
+      #
+      # Returns a Query object if one could be found, nil otherwise.
+      def find_query(id)
+        @queries.find { |query| query.id == id }
+      end
+
+      # Finds a file sample by the given ID.
+      #
+      # id - The query ID as a String.
+      #
+      # Returns a FileSample object if one could be found, nil otherwise.
+      def find_file_sample(id)
+        @file_samples.find { |sample| sample.id == id }
+      end
+
+      def profile_lines
+        retval = nil
+
+        if Sherlock.enable_line_profiler?
+          retval, @file_samples = LineProfiler.new.profile { yield }
+        else
+          retval = yield
+        end
+
+        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 track_view(path)
+        @view_counts[path] += 1
+      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
+end