Fix problematic Database/MultipleDatabases offenses

- Fix places where we are ignoring the Database/MultipleDatabase rule.
Instead of using ActiveRecord::Base connection/transaction,
we are using the proper class.

Changelog: changed
Related to https://gitlab.com/gitlab-org/gitlab/-/issues/335808
EE: true

app/mailers/previews/notify_preview.rb

@@ -246,7 +246,7 @@ class NotifyPreview < ActionMailer::Preview
   def cleanup
     email = nil
 
-    ActiveRecord::Base.transaction do # rubocop: disable Database/MultipleDatabases
+    ApplicationRecord.transaction do
       email = yield
       raise ActiveRecord::Rollback
     end

app/models/internal_id.rb

@@ -57,7 +57,7 @@ class InternalId < ApplicationRecord
       self.internal_id_transactions_total.increment(
         operation: operation,
         usage: usage.to_s,
-        in_transaction: ActiveRecord::Base.connection.transaction_open?.to_s # rubocop: disable Database/MultipleDatabases
+        in_transaction: InternalId.connection.transaction_open?.to_s
       )
     end
 

app/services/auto_merge/base_service.rb

@@ -6,7 +6,7 @@ module AutoMerge
     include MergeRequests::AssignsMergeParams
 
     def execute(merge_request)
-      ActiveRecord::Base.transaction do # rubocop: disable Database/MultipleDatabases
+      ApplicationRecord.transaction do
         register_auto_merge_parameters!(merge_request)
         yield if block_given?
       end
@@ -29,7 +29,7 @@ module AutoMerge
     end
 
     def cancel(merge_request)
-      ActiveRecord::Base.transaction do # rubocop: disable Database/MultipleDatabases
+      ApplicationRecord.transaction do
         clear_auto_merge_parameters!(merge_request)
         yield if block_given?
       end
@@ -41,7 +41,7 @@ module AutoMerge
     end
 
     def abort(merge_request, reason)
-      ActiveRecord::Base.transaction do # rubocop: disable Database/MultipleDatabases
+      ApplicationRecord.transaction do
         clear_auto_merge_parameters!(merge_request)
         yield if block_given?
       end

app/services/deployments/update_environment_service.rb

@@ -26,7 +26,7 @@ module Deployments
     end
 
     def update_environment(deployment)
-      ActiveRecord::Base.transaction do # rubocop: disable Database/MultipleDatabases
+      ApplicationRecord.transaction do
         # Renew attributes at update
         renew_external_url
         renew_auto_stop_in

ee/lib/ee/gitlab/checks/push_rule_check.rb

@@ -99,8 +99,8 @@ module EE
 
               yield
             end
-          ensure # rubocop: disable Layout/RescueEnsureAlignment
-            ActiveRecord::Base.clear_active_connections! # rubocop: disable Database/MultipleDatabases
+          ensure
+            ApplicationRecord.clear_active_connections!
           end
         end
       end

lib/gitlab/database/grant.rb

@@ -10,7 +10,7 @@ module Gitlab
         # We _must not_ use quote_table_name as this will produce double
         # quotes on PostgreSQL and for "has_table_privilege" we need single
         # quotes.
-        connection = ActiveRecord::Base.connection # rubocop: disable Database/MultipleDatabases
+        connection = ApplicationRecord.connection
         quoted_table = connection.quote(table)
 
         begin

lib/gitlab/database/load_balancing/setup.rb

@@ -104,11 +104,9 @@ module Gitlab
             end
           end
 
-          # rubocop:disable Database/MultipleDatabases
           def connection
-            use_model_load_balancing? ? super : ActiveRecord::Base.connection
+            use_model_load_balancing? ? super : ApplicationRecord.connection
           end
-          # rubocop:enable Database/MultipleDatabases
         end
       end
     end

spec/lib/gitlab/metrics/samplers/database_sampler_spec.rb

@@ -62,7 +62,7 @@ RSpec.describe Gitlab::Metrics::Samplers::DatabaseSampler do
       end
 
       context 'when replica hosts are configured' do
-        let(:main_load_balancer) { ActiveRecord::Base.load_balancer } # rubocop:disable Database/MultipleDatabases
+        let(:main_load_balancer) { ApplicationRecord.load_balancer }
         let(:main_replica_host) { main_load_balancer.host }
 
         let(:ci_load_balancer) { double(:load_balancer, host_list: ci_host_list, configuration: configuration) }
@@ -117,7 +117,7 @@ RSpec.describe Gitlab::Metrics::Samplers::DatabaseSampler do
       end
 
       context 'when the base model has replica connections' do
-        let(:main_load_balancer) { ActiveRecord::Base.load_balancer } # rubocop:disable Database/MultipleDatabases
+        let(:main_load_balancer) { ApplicationRecord.load_balancer }
         let(:main_replica_host) { main_load_balancer.host }
 
         let(:ci_load_balancer) { double(:load_balancer, host_list: ci_host_list, configuration: configuration) }

spec/models/application_record_spec.rb

@@ -147,22 +147,20 @@ RSpec.describe ApplicationRecord do
       end
     end
 
-    # rubocop:disable Database/MultipleDatabases
     it 'increments a counter when a transaction is created in ActiveRecord' do
       expect(described_class.connection.transaction_open?).to be false
 
       expect(::Gitlab::Database::Metrics)
         .to receive(:subtransactions_increment)
-        .with('ActiveRecord::Base')
+        .with('ApplicationRecord')
         .once
 
-      ActiveRecord::Base.transaction do
-        ActiveRecord::Base.transaction(requires_new: true) do
-          expect(ActiveRecord::Base.connection.transaction_open?).to be true
+      ApplicationRecord.transaction do
+        ApplicationRecord.transaction(requires_new: true) do
+          expect(ApplicationRecord.connection.transaction_open?).to be true
         end
       end
     end
-    # rubocop:enable Database/MultipleDatabases
   end
 
   describe '.with_fast_read_statement_timeout' do

spec/models/internal_id_spec.rb

@@ -87,7 +87,7 @@ RSpec.describe InternalId do
 
     context 'when executed outside of transaction' do
       it 'increments counter with in_transaction: "false"' do
-        allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases
+        allow(ApplicationRecord.connection).to receive(:transaction_open?) { false }
 
         expect(InternalId.internal_id_transactions_total).to receive(:increment)
           .with(operation: :generate, usage: 'issues', in_transaction: 'false').and_call_original
@@ -146,7 +146,7 @@ RSpec.describe InternalId do
       let(:value) { 2 }
 
       it 'increments counter with in_transaction: "false"' do
-        allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases
+        allow(ApplicationRecord.connection).to receive(:transaction_open?) { false }
 
         expect(InternalId.internal_id_transactions_total).to receive(:increment)
           .with(operation: :reset, usage: 'issues', in_transaction: 'false').and_call_original
@@ -217,7 +217,7 @@ RSpec.describe InternalId do
 
     context 'when executed outside of transaction' do
       it 'increments counter with in_transaction: "false"' do
-        allow(ActiveRecord::Base.connection).to receive(:transaction_open?) { false } # rubocop: disable Database/MultipleDatabases
+        allow(ApplicationRecord.connection).to receive(:transaction_open?) { false }
 
         expect(InternalId.internal_id_transactions_total).to receive(:increment)
           .with(operation: :track_greatest, usage: 'issues', in_transaction: 'false').and_call_original

spec/support_specs/database/multiple_databases_spec.rb

@@ -42,7 +42,7 @@ RSpec.describe 'Database::MultipleDatabases' do
       context 'when reconnect is true' do
         it 'does not raise exception' do
           with_reestablished_active_record_base(reconnect: true) do
-            expect { ActiveRecord::Base.connection.execute("SELECT 1") }.not_to raise_error # rubocop:disable Database/MultipleDatabases
+            expect { ApplicationRecord.connection.execute("SELECT 1") }.not_to raise_error
           end
         end
       end
@@ -50,7 +50,7 @@ RSpec.describe 'Database::MultipleDatabases' do
       context 'when reconnect is false' do
         it 'does raise exception' do
           with_reestablished_active_record_base(reconnect: false) do
-            expect { ActiveRecord::Base.connection.execute("SELECT 1") }.to raise_error(ActiveRecord::ConnectionNotEstablished) # rubocop:disable Database/MultipleDatabases
+            expect { ApplicationRecord.connection.execute("SELECT 1") }.to raise_error(ActiveRecord::ConnectionNotEstablished)
           end
         end
       end