Merge branch 'fix/cycle-analytics-events-limit' into 'master'

app/assets/javascripts/cycle_analytics/components/stage_plan_component.js.es6

@@ -13,6 +13,12 @@
       <div>
         <div class="events-description">
           {{ stage.description }}
+          <span v-if="items.length === 50" class="events-info pull-right">
+            <i class="fa fa-warning has-tooltip"
+              title="Limited to showing 50 events at most"
+              data-placement="top"></i>
+            Showing 50 events
+          </span>
         </div>
         <ul class="stage-event-list">
           <li v-for="commit in items" class="stage-event-item">

app/assets/stylesheets/pages/cycle_analytics.scss

@@ -284,7 +284,11 @@
 
     .events-description {
       line-height: 65px;
-      padding-left: $gl-padding;
+      padding: 0 $gl-padding;
+    }
+
+    .events-info {
+      color: $gl-text-color-secondary;
     }
   }
 

changelogs/unreleased/fix-cycle-analytics-events-limit.yml

+---
+title: Add limit to the number of events showed in cycle analytics
+merge_request: 
+author: 

lib/gitlab/cycle_analytics/base_event_fetcher.rb

@@ -5,6 +5,8 @@ module Gitlab
 
       attr_reader :projections, :query, :stage, :order
 
+      MAX_EVENTS = 50
+
       def initialize(project:, stage:, options:)
         @project = project
         @stage = stage
@@ -38,7 +40,7 @@ module Gitlab
       def events_query
         diff_fn = subtract_datetimes_diff(base_query, @options[:start_time_attrs], @options[:end_time_attrs])
 
-        base_query.project(extract_diff_epoch(diff_fn).as('total_time'), *projections).order(order.desc)
+        base_query.project(extract_diff_epoch(diff_fn).as('total_time'), *projections).order(order.desc).take(MAX_EVENTS)
       end
 
       def default_order

spec/lib/gitlab/cycle_analytics/base_event_fetcher_spec.rb

+require 'spec_helper'
+
+describe Gitlab::CycleAnalytics::BaseEventFetcher do
+  let(:max_events) { 2 }
+  let(:project) { create(:project) }
+  let(:user) { create(:user, :admin) }
+  let(:start_time_attrs) { Issue.arel_table[:created_at] }
+  let(:end_time_attrs) { [Issue::Metrics.arel_table[:first_associated_with_milestone_at]] }
+  let(:options) do 
+    { start_time_attrs: start_time_attrs,
+      end_time_attrs: end_time_attrs,
+      from: 30.days.ago } 
+  end
+
+  subject do
+    described_class.new(project: project,
+                        stage: :issue,
+                        options: options).fetch
+  end
+
+  before do
+    allow_any_instance_of(Gitlab::ReferenceExtractor).to receive(:issues).and_return(Issue.all)
+    allow_any_instance_of(Gitlab::CycleAnalytics::BaseEventFetcher).to receive(:serialize) do |event|
+      event
+    end
+
+    stub_const('Gitlab::CycleAnalytics::BaseEventFetcher::MAX_EVENTS', max_events)
+
+    setup_events(count: 3)
+  end
+
+  it 'limits the rows to the max number' do
+    expect(subject.count).to eq(max_events)
+  end
+
+  def setup_events(count:)
+    count.times do
+      issue = create(:issue, project: project, created_at: 2.days.ago)
+      milestone = create(:milestone, project: project)
+
+      issue.update(milestone: milestone)
+      create_merge_request_closing_issue(issue)
+    end
+  end
+end