Always use internal ID tables in development and production

To avoid quiet failures that cause consistency errors in the database,
we should now assume that the internal_ids table is available since
we've had this table for close to a year.

For tests that have migrations, we make this check thread-safe via
SafeRequestStore.

Closes https://gitlab.com/gitlab-org/gitlab-ce/issues/60718

app/models/internal_id.rb

@@ -87,12 +87,16 @@ class InternalId < ApplicationRecord
     end
 
     def available?
-      @available_flag ||= ActiveRecord::Migrator.current_version >= REQUIRED_SCHEMA_VERSION # rubocop:disable Gitlab/PredicateMemoization
+      return true unless Rails.env.test?
+
+      Gitlab::SafeRequestStore.fetch(:internal_ids_available_flag) do
+        ActiveRecord::Migrator.current_version >= REQUIRED_SCHEMA_VERSION
+      end
     end
 
     # Flushes cached information about schema
     def reset_column_information
-      @available_flag = nil
+      Gitlab::SafeRequestStore[:internal_ids_available_flag] = nil
       super
     end
   end

changelogs/unreleased/sh-disable-internal-ids-available-check.yml

+---
+title: Always use internal ID tables in development and production
+merge_request: 27544
+author:
+type: fixed

spec/models/internal_id_spec.rb

@@ -93,7 +93,7 @@ describe InternalId do
       before do
         described_class.reset_column_information
         # Project factory will also call the current_version
-        expect(ActiveRecord::Migrator).to receive(:current_version).twice.and_return(InternalId::REQUIRED_SCHEMA_VERSION - 1)
+        expect(ActiveRecord::Migrator).to receive(:current_version).at_least(:once).and_return(InternalId::REQUIRED_SCHEMA_VERSION - 1)
       end
 
       let(:init) { double('block') }
@@ -104,6 +104,15 @@ describe InternalId do
         expect(init).to receive(:call).with(issue).and_return(val)
         expect(subject).to eq(val + 1)
       end
+
+      it 'always attempts to generate internal IDs in production mode' do
+        allow(Rails.env).to receive(:test?).and_return(false)
+        val = rand(1..100)
+        generator = double(generate: val)
+        expect(InternalId::InternalIdGenerator).to receive(:new).and_return(generator)
+
+        expect(subject).to eq(val)
+      end
     end
   end