Add gitlab:db:active task

To be used for setting up GEO replication in the omnibus-gitalb package.
Intended to help prevent users from accidentally deleting actively used
databases.

* Returns 0 if there is sign that the database has been modified by the
  user
* Returns 1 if there is no sign that the database has been modified by
  the user

changelogs/unreleased/add-gitlab-db-active-task.yml

+---
+title: Add gitlab:db:active task
+merge_request: 48083
+author:
+type: fixed

lib/tasks/gitlab/db.rake

@@ -203,5 +203,25 @@ namespace :gitlab do
       Gitlab::AppLogger.error(e)
       raise
     end
+
+    desc 'Check if there have been user additions to the database'
+    task active: :environment do
+      if ActiveRecord::Base.connection.migration_context.needs_migration?
+        puts "Migrations pending. Database not active"
+        exit 1
+      end
+
+      # A list of projects that GitLab creates automatically on install/upgrade
+      # gc = Gitlab::CurrentSettings.current_application_settings
+      seed_projects = [Gitlab::CurrentSettings.current_application_settings.self_monitoring_project]
+
+      if (Project.count - seed_projects.count {|x| !x.nil? }).eql?(0)
+        puts "No user created projects. Database not active"
+        exit 1
+      end
+
+      puts "Found user created projects. Database active"
+      exit 0
+    end
   end
 end

spec/tasks/gitlab/db_rake_spec.rb

@@ -261,6 +261,34 @@ RSpec.describe 'gitlab:db namespace rake task' do
     end
   end
 
+  describe 'active' do
+    using RSpec::Parameterized::TableSyntax
+
+    let(:task) { 'gitlab:db:active' }
+    let(:self_monitoring) { double('self_monitoring') }
+
+    where(:needs_migration, :self_monitoring_project, :project_count, :exit_status, :exit_code) do
+      true | nil | nil | 1 | false
+      false | :self_monitoring | 1 | 1 | false
+      false | nil | 0 | 1 | false
+      false | :self_monitoring | 2 | 0 | true
+    end
+
+    with_them do
+      it 'exits 0 or 1 depending on user modifications to the database' do
+        allow_any_instance_of(ActiveRecord::MigrationContext).to receive(:needs_migration?).and_return(needs_migration)
+        allow_any_instance_of(ApplicationSetting).to receive(:self_monitoring_project).and_return(self_monitoring_project)
+        allow(Project).to receive(:count).and_return(project_count)
+
+        expect { run_rake_task(task) }.to raise_error do |error|
+          expect(error).to be_a(SystemExit)
+          expect(error.status).to eq(exit_status)
+          expect(error.success?).to be(exit_code)
+        end
+      end
+    end
+  end
+
   def run_rake_task(task_name, arguments = '')
     Rake::Task[task_name].reenable
     Rake.application.invoke_task("#{task_name}#{arguments}")