Return warnings for performance bar from backend

For each DetailedView subclass, we add a `warnings` array to:

1. The top-level response.
2. Each individual call under the `details` key.

We use the `.thresholds` hash on the DetailedView to determine what's a
warning. If that hash is empty (the default), then the warnings array
will always be empty.

lib/peek/views/active_record.rb

@@ -3,6 +3,24 @@
 module Peek
   module Views
     class ActiveRecord < DetailedView
+      DEFAULT_THRESHOLDS = {
+        calls: 100,
+        duration: 3,
+        individual_call: 1
+      }.freeze
+
+      THRESHOLDS = {
+        production: {
+          calls: 100,
+          duration: 15,
+          individual_call: 5
+        }
+      }.freeze
+
+      def self.thresholds
+        @thresholds ||= THRESHOLDS.fetch(Rails.env.to_sym, DEFAULT_THRESHOLDS)
+      end
+
       private
 
       def setup_subscribers

lib/peek/views/detailed_view.rb

@@ -3,11 +3,16 @@
 module Peek
   module Views
     class DetailedView < View
+      def self.thresholds
+        {}
+      end
+
       def results
         {
-          duration: formatted_duration,
+          duration: format_duration(duration),
           calls: calls,
-          details: details
+          details: details,
+          warnings: warnings
         }
       end
 
@@ -18,30 +23,48 @@ module Peek
       private
 
       def duration
-        detail_store.map { |entry| entry[:duration] }.sum # rubocop:disable CodeReuse/ActiveRecord
+        detail_store.map { |entry| entry[:duration] }.sum * 1000 # rubocop:disable CodeReuse/ActiveRecord
       end
 
       def calls
         detail_store.count
       end
 
+      def details
+        call_details
+          .sort { |a, b| b[:duration] <=> a[:duration] }
+          .map(&method(:format_call_details))
+      end
+
+      def warnings
+        [
+          warning_for(calls, self.class.thresholds[:calls], label: "#{key} calls"),
+          warning_for(duration, self.class.thresholds[:duration], label: "#{key} duration")
+        ].flatten.compact
+      end
+
       def call_details
         detail_store
       end
 
       def format_call_details(call)
-        call.merge(duration: (call[:duration] * 1000).round(3))
-      end
+        duration = (call[:duration] * 1000).round(3)
 
-      def details
-        call_details
-          .sort { |a, b| b[:duration] <=> a[:duration] }
-          .map(&method(:format_call_details))
+        call.merge(duration: duration,
+                   warnings: warning_for(duration, self.class.thresholds[:individual_call]))
       end
 
-      def formatted_duration
-        ms = duration * 1000
+      def warning_for(actual, threshold, label: nil)
+        if threshold && actual > threshold
+          prefix = "#{label}: " if label
+
+          ["#{prefix}#{actual} over #{threshold}"]
+        else
+          []
+        end
+      end
 
+      def format_duration(ms)
         if ms >= 1000
           "%.2fms" % ms
         else

lib/peek/views/gitaly.rb

@@ -3,6 +3,24 @@
 module Peek
   module Views
     class Gitaly < DetailedView
+      DEFAULT_THRESHOLDS = {
+        calls: 30,
+        duration: 1,
+        individual_call: 0.5
+      }.freeze
+
+      THRESHOLDS = {
+        production: {
+          calls: 30,
+          duration: 1,
+          individual_call: 0.5
+        }
+      }.freeze
+
+      def self.thresholds
+        @thresholds ||= THRESHOLDS.fetch(Rails.env.to_sym, DEFAULT_THRESHOLDS)
+      end
+
       private
 
       def duration

lib/peek/views/rugged.rb

@@ -12,7 +12,7 @@ module Peek
       private
 
       def duration
-        ::Gitlab::RuggedInstrumentation.query_time
+        ::Gitlab::RuggedInstrumentation.query_time_ms
       end
 
       def calls

spec/lib/peek/views/detailed_view_spec.rb

+# frozen_string_literal: true
+
+require 'fast_spec_helper'
+
+describe Peek::Views::DetailedView, :request_store do
+  context 'when a class defines thresholds' do
+    let(:threshold_view) do
+      Class.new(described_class) do
+        def self.thresholds
+          {
+            calls: 1,
+            duration: 10,
+            individual_call: 5
+          }
+        end
+
+        def key
+          'threshold-view'
+        end
+      end.new
+    end
+
+    context 'when the results exceed the calls threshold' do
+      before do
+        allow(threshold_view)
+          .to receive(:detail_store).and_return([{ duration: 0.001 }, { duration: 0.001 }])
+      end
+
+      it 'adds a warning to the results key' do
+        expect(threshold_view.results).to include(warnings: [a_string_matching('threshold-view calls')])
+      end
+    end
+
+    context 'when the results exceed the duration threshold' do
+      before do
+        allow(threshold_view)
+          .to receive(:detail_store).and_return([{ duration: 0.011 }])
+      end
+
+      it 'adds a warning to the results key' do
+        expect(threshold_view.results).to include(warnings: [a_string_matching('threshold-view duration')])
+      end
+    end
+
+    context 'when a single call exceeds the duration threshold' do
+      before do
+        allow(threshold_view)
+          .to receive(:detail_store).and_return([{ duration: 0.001 }, { duration: 0.006 }])
+      end
+
+      it 'adds a warning to that call detail entry' do
+        expect(threshold_view.results)
+          .to include(details: a_collection_containing_exactly(
+            { duration: 1.0, warnings: [] },
+                       { duration: 6.0, warnings: ['6.0 over 5'] }
+          ))
+      end
+    end
+  end
+
+  context 'when a view does not define thresholds' do
+    let(:no_threshold_view) { Class.new(described_class).new }
+
+    before do
+      allow(no_threshold_view)
+        .to receive(:detail_store).and_return([{ duration: 100 }, { duration: 100 }])
+    end
+
+    it 'does not add warnings to the top level' do
+      expect(no_threshold_view.results).to include(warnings: [])
+    end
+
+    it 'does not add warnings to call details entries' do
+      expect(no_threshold_view.results)
+        .to include(details: a_collection_containing_exactly(
+          { duration: 100000, warnings: [] },
+                     { duration: 100000, warnings: [] }
+        ))
+    end
+  end
+end

spec/lib/peek/views/redis_detailed_spec.rb

@@ -21,10 +21,10 @@ describe Peek::Views::RedisDetailed, :request_store do
 
       expect(subject.results[:details].count).to eq(1)
       expect(subject.results[:details].first)
-        .to eq({
-                 cmd: expected,
-                 duration: 1000
-               })
+        .to include({
+                      cmd: expected,
+                      duration: 1000
+                    })
     end
   end