Added cron to prune events older than 12 months.

Since contribution calendar shows only 12 months of activity,
events older than that time are not visible anywhere and can be
safely pruned saving big amount of database storage.

Fixes #21164

CHANGELOG

@@ -4,6 +4,7 @@ v 8.12.0 (unreleased)
   - Add ability to fork to a specific namespace using API. (ritave)
   - Cleanup misalignments in Issue list view !6206
   - Prepend blank line to `Closes` message on merge request linked to issue (lukehowell)
+  - Prune events older than 12 months.
   - Filter tags by name !6121
   - Make push events have equal vertical spacing.
   - Add two-factor recovery endpoint to internal API !5510

app/workers/prune_old_events_worker.rb

+class PruneOldEventsWorker
+  include Sidekiq::Worker
+
+  def perform
+    # Contribution calendar shows maximum 12 months of events
+    Event.where('created_at < ?', (12.months + 1.day).ago).destroy_all
+  end
+end

config/initializers/1_settings.rb

@@ -299,6 +299,9 @@ Settings.cron_jobs['remove_expired_members_worker']['job_class'] = 'RemoveExpire
 Settings.cron_jobs['remove_expired_group_links_worker'] ||= Settingslogic.new({})
 Settings.cron_jobs['remove_expired_group_links_worker']['cron'] ||= '10 0 * * *'
 Settings.cron_jobs['remove_expired_group_links_worker']['job_class'] = 'RemoveExpiredGroupLinksWorker'
+Settings.cron_jobs['prune_old_events_worker'] ||= Settingslogic.new({})
+Settings.cron_jobs['prune_old_events_worker']['cron'] ||= '0 0 * * *'
+Settings.cron_jobs['prune_old_events_worker']['job_class'] = 'PruneOldEventsWorker'
 
 #
 # GitLab Shell

spec/workers/prune_old_events_worker_spec.rb

+require 'spec_helper'
+
+describe PruneOldEventsWorker do
+  describe '#perform' do
+    let!(:expired_event) { create(:event, author_id: 0, created_at: 13.months.ago) }
+    let!(:not_expired_event) { create(:event, author_id: 0,  created_at: 1.day.ago) }
+    let!(:exactly_12_months_event) { create(:event, author_id: 0, created_at: 12.months.ago) }
+
+    it 'prunes events older than 12 months' do
+      expect { subject.perform }.to change { Event.count }.by(-1)
+      expect(Event.find_by(id: expired_event.id)).to be_nil
+    end
+
+    it 'leaves fresh events' do
+      subject.perform
+      expect(not_expired_event.reload).to be_present
+    end
+
+    it 'leaves events from exactly 12 months ago' do
+      subject.perform
+      expect(exactly_12_months_event).to be_present
+    end
+  end
+end