Add metric to track projects with atleast 1 alert to usage ping data

ee/app/models/prometheus_alert.rb

@@ -23,6 +23,11 @@ class PrometheusAlert < ActiveRecord::Base
 
   scope :for_metric, -> (metric) { where(prometheus_metric: metric) }
 
+  def self.distinct_projects
+    sub_query = self.group(:project_id).select(1)
+    self.from(sub_query)
+  end
+
   def self.operator_to_enum(op)
     OPERATORS_MAP.invert.fetch(op)
   end

ee/changelogs/unreleased/rpereira2-7828_add-alerts-count.yml

+---
+title: Add a metric to the usage ping data to track the number of projects with at least one alert
+merge_request: 8058
+author:
+type: other

ee/lib/ee/gitlab/usage_data.rb

@@ -99,7 +99,8 @@ module EE
           ldap_keys: count(::LDAPKey),
           ldap_users: count(::User.ldap),
           projects_reporting_ci_cd_back_to_github: count(::GithubService.without_defaults.active),
-          projects_mirrored_with_pipelines_enabled: projects_mirrored_with_pipelines_enabled
+          projects_mirrored_with_pipelines_enabled: projects_mirrored_with_pipelines_enabled,
+          projects_with_prometheus_alerts: count(PrometheusAlert.distinct_projects)
         }).merge(service_desk_counts).merge(security_products_usage)
 
         usage_data

ee/spec/lib/gitlab/usage_data_spec.rb

@@ -14,6 +14,10 @@ describe Gitlab::UsageData do
       create(:ci_build, name: 'dependency_scanning', pipeline: pipeline)
       create(:ci_build, name: 'license_management', pipeline: pipeline)
       create(:ci_build, name: 'sast', pipeline: pipeline)
+
+      create(:prometheus_alert, project: projects[0])
+      create(:prometheus_alert, project: projects[0])
+      create(:prometheus_alert, project: projects[1])
     end
 
     subject { described_class.data }
@@ -54,7 +58,10 @@ describe Gitlab::UsageData do
         dependency_scanning_jobs
         license_management_jobs
         sast_jobs
+        projects_with_prometheus_alerts
       ))
+
+      expect(count_data[:projects_with_prometheus_alerts]).to eq(2)
     end
 
     it 'gathers security products usage data' do

ee/spec/models/prometheus_alert_spec.rb

@@ -6,6 +6,23 @@ describe PrometheusAlert do
   set(:project) { build(:project) }
   let(:metric) { build(:prometheus_metric) }
 
+  describe '.distinct_projects' do
+    let(:project1) { create(:project) }
+    let(:project2) { create(:project) }
+
+    before do
+      create(:prometheus_alert, project: project1)
+      create(:prometheus_alert, project: project1)
+      create(:prometheus_alert, project: project2)
+    end
+
+    subject { described_class.distinct_projects.count }
+
+    it 'returns a count of all distinct projects which have an alert' do
+      expect(subject).to eq(2)
+    end
+  end
+
   describe 'associations' do
     it { is_expected.to belong_to(:project) }
     it { is_expected.to belong_to(:environment) }