Add issues metric instrumentation

  - Add CountIssuesMetric
  - Add CountUsersCreatingIssuesMetric

config/metrics/counts_28d/20210216181139_issues.yml

 ---
 key_path: usage_activity_by_stage_monthly.plan.issues
-description: Count of MAU creating issues
+description: Count of users creating Issues in last 28 days.
 product_section: dev
-product_stage: plan 
+product_stage: plan
 product_group: group::project management
-product_category: issue_tracking 
+product_category: issue_tracking
 value_type: number
 status: data_available
 time_frame: 28d
 data_source: database
+instrumentation_class: 'Gitlab::Usage::Metrics::Instrumentations::CountUsersCreatingIssuesMetric'
 distribution:
 - ce
-- ee 
+- ee
 tier:
 - free
-- premium 
+- premium
 - ultimate

config/metrics/counts_all/20210216181102_issues.yml

@@ -9,6 +9,7 @@ value_type: number
 status: data_available
 time_frame: all
 data_source: database
+instrumentation_class: 'Gitlab::Usage::Metrics::Instrumentations::CountIssuesMetric'
 distribution:
 - ce
 - ee

config/metrics/counts_all/20210216181115_issues.yml

@@ -9,6 +9,7 @@ value_type: number
 status: data_available
 time_frame: all
 data_source: database
+instrumentation_class: 'Gitlab::Usage::Metrics::Instrumentations::CountUsersCreatingIssuesMetric'
 distribution:
 - ce
 - ee

doc/development/usage_ping/dictionary.md

@@ -18256,7 +18256,7 @@ Tiers: `free`
 
 ### `usage_activity_by_stage_monthly.plan.issues`
 
-Count of MAU creating issues
+Count of users creating Issues in last 28 days.
 
 [YAML definition](https://gitlab.com/gitlab-org/gitlab/-/blob/master/config/metrics/counts_28d/20210216181139_issues.yml)
 

lib/gitlab/usage/metrics/instrumentations/count_issues_metric.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Usage
+    module Metrics
+      module Instrumentations
+        class CountIssuesMetric < DatabaseMetric
+          operation :count
+
+          start { Issue.minimum(:id) }
+          finish { Issue.maximum(:id) }
+
+          relation { Issue }
+        end
+      end
+    end
+  end
+end

lib/gitlab/usage/metrics/instrumentations/count_users_creating_issues_metric.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Usage
+    module Metrics
+      module Instrumentations
+        class CountUsersCreatingIssuesMetric < DatabaseMetric
+          operation :distinct_count, column: :author_id
+
+          relation { Issue }
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/usage/metrics/instrumentations/count_issues_metric_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::CountIssuesMetric do
+  let_it_be(:issue) { create(:issue) }
+
+  it_behaves_like 'a correct instrumented metric value', { time_frame: 'all', data_source: 'database' }, 1
+end

spec/lib/gitlab/usage/metrics/instrumentations/count_users_creating_issues_metric_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::CountUsersCreatingIssuesMetric do
+  let_it_be(:author) { create(:user) }
+  let_it_be(:issues) { create_list(:issue, 2, author: author, created_at: 4.days.ago) }
+  let_it_be(:old_issue) { create(:issue, author: author, created_at: 2.months.ago) }
+
+  context 'with all time frame' do
+    it_behaves_like 'a correct instrumented metric value', { time_frame: 'all', data_source: 'database' }, 1
+  end
+
+  context 'for 28d time frame' do
+    it_behaves_like 'a correct instrumented metric value', { time_frame: '28d', data_source: 'database' }, 1
+  end
+end

spec/lib/gitlab/usage_data_metrics_spec.rb

@@ -20,6 +20,18 @@ RSpec.describe Gitlab::UsageDataMetrics do
       it 'includes top level keys' do
         expect(subject).to include(:uuid)
       end
+
+      it 'includes counts keys' do
+        expect(subject[:counts]).to include(:issues)
+      end
+
+      it 'includes usage_activity_by_stage keys' do
+        expect(subject[:usage_activity_by_stage][:plan]).to include(:issues)
+      end
+
+      it 'includes usage_activity_by_stage_monthly keys' do
+        expect(subject[:usage_activity_by_stage_monthly][:plan]).to include(:issues)
+      end
     end
   end
 end