Add project with alerts created metric

changelogs/unreleased/263552-number-of-projects-active-alerts.yml

+---
+title: Add metric count for projects with alerts created
+merge_request: 46636
+author:
+type: added

lib/gitlab/usage_data.rb

@@ -160,6 +160,7 @@ module Gitlab
             projects_with_tracing_enabled: count(ProjectTracingSetting),
             projects_with_error_tracking_enabled: count(::ErrorTracking::ProjectErrorTrackingSetting.where(enabled: true)),
             projects_with_alerts_service_enabled: count(AlertsService.active),
+            projects_with_alerts_created: distinct_count(::AlertManagement::Alert, :project_id),
             projects_with_prometheus_alerts: distinct_count(PrometheusAlert, :project_id),
             projects_with_terraform_reports: distinct_count(::Ci::JobArtifact.terraform_reports, :project_id),
             projects_with_terraform_states: distinct_count(::Terraform::State, :project_id),
@@ -215,7 +216,8 @@ module Gitlab
             # rubocop: enable UsageData/LargeTable:
             packages: count(::Packages::Package.where(last_28_days_time_period)),
             personal_snippets: count(PersonalSnippet.where(last_28_days_time_period)),
-            project_snippets: count(ProjectSnippet.where(last_28_days_time_period))
+            project_snippets: count(ProjectSnippet.where(last_28_days_time_period)),
+            projects_with_alerts_created: distinct_count(::AlertManagement::Alert.where(last_28_days_time_period), :project_id)
           }.merge(
             snowplow_event_counts(last_28_days_time_period(column: :collector_tstamp))
           ).tap do |data|

spec/lib/gitlab/usage_data_spec.rb

@@ -302,6 +302,7 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
         operations_dashboard_default_dashboard: 2,
         projects_with_tracing_enabled: 2
       )
+
       expect(described_class.usage_activity_by_stage_monitor(described_class.last_28_days_time_period)).to include(
         clusters: 1,
         clusters_applications_prometheus: 1,
@@ -463,6 +464,7 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
       expect(count_data[:projects_with_prometheus_alerts]).to eq(2)
       expect(count_data[:projects_with_terraform_reports]).to eq(2)
       expect(count_data[:projects_with_terraform_states]).to eq(2)
+      expect(count_data[:projects_with_alerts_created]).to eq(1)
       expect(count_data[:protected_branches]).to eq(2)
       expect(count_data[:protected_branches_except_default]).to eq(1)
       expect(count_data[:terraform_reports]).to eq(6)
@@ -604,6 +606,7 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
         create(:deployment, :success, deployment_options)
         create(:project_snippet, project: project, created_at: n.days.ago)
         create(:personal_snippet, created_at: n.days.ago)
+        create(:alert_management_alert, project: project, created_at: n.days.ago)
       end
 
       stub_application_setting(self_monitoring_project: project)
@@ -624,6 +627,7 @@ RSpec.describe Gitlab::UsageData, :aggregate_failures do
       expect(counts_monthly[:snippets]).to eq(2)
       expect(counts_monthly[:personal_snippets]).to eq(1)
       expect(counts_monthly[:project_snippets]).to eq(1)
+      expect(counts_monthly[:projects_with_alerts_created]).to eq(1)
       expect(counts_monthly[:packages]).to eq(1)
       expect(counts_monthly[:promoted_issues]).to eq(1)
     end