The validate_config task should reconnect to the main database

It should not keep the geo as "ActiveRecord::Base" connection

lib/tasks/gitlab/db/validate_config.rake

@@ -6,7 +6,7 @@ namespace :gitlab do
   namespace :db do
     desc 'Validates `config/database.yml` to ensure a correct behavior is configured'
     task validate_config: :environment do
-      should_reconnect = ActiveRecord::Base.connection_pool.active_connection?
+      original_db_config = ActiveRecord::Base.connection_db_config
 
       # The include_replicas: is a legacy name to fetch all hidden entries (replica: true or database_tasks: false)
       # Once we upgrade to Rails 7.x this should be changed to `include_hidden: true`
@@ -97,9 +97,7 @@ namespace :gitlab do
       end
 
     ensure
-      if should_reconnect
-        ActiveRecord::Base.establish_connection(ActiveRecord::Tasks::DatabaseTasks.env.to_sym) # rubocop: disable Database/EstablishConnection
-      end
+      ActiveRecord::Base.establish_connection(original_db_config) # rubocop: disable Database/EstablishConnection
     end
 
     Rake::Task['db:migrate'].enhance(['gitlab:db:validate_config'])

spec/tasks/gitlab/db/validate_config_rake_spec.rb

@@ -46,6 +46,12 @@ RSpec.describe 'gitlab:db:validate_config', :silence_stdout do
         expect { run_rake_task('gitlab:db:validate_config') }.not_to raise_error
       end
 
+      it 'always re-establishes ActiveRecord::Base connection to main config' do
+        run_rake_task('gitlab:db:validate_config')
+
+        expect(ActiveRecord::Base.connection_db_config.configuration_hash).to include(main_database_config) # rubocop: disable Database/MultipleDatabases
+      end
+
       it 'if GITLAB_VALIDATE_DATABASE_CONFIG is set' do
         stub_env('GITLAB_VALIDATE_DATABASE_CONFIG', '1')
         allow(Gitlab).to receive(:dev_or_test_env?).and_return(false)
@@ -78,6 +84,12 @@ RSpec.describe 'gitlab:db:validate_config', :silence_stdout do
         expect { run_rake_task('gitlab:db:validate_config') }.to raise_error(match)
       end
 
+      it 'always re-establishes ActiveRecord::Base connection to main config' do
+        expect { run_rake_task('gitlab:db:validate_config') }.to raise_error(match)
+
+        expect(ActiveRecord::Base.connection_db_config.configuration_hash).to include(main_database_config) # rubocop: disable Database/MultipleDatabases
+      end
+
       it 'if GITLAB_VALIDATE_DATABASE_CONFIG=1' do
         stub_env('GITLAB_VALIDATE_DATABASE_CONFIG', '1')