Merge branch 'remove-connection-config-caching' into 'master'

Remove caching of Connection#config

See merge request gitlab-org/gitlab!67047

lib/gitlab/database/connection.rb

@@ -34,12 +34,17 @@ module Gitlab
         Gitlab::Runtime.max_threads + headroom
       end
 
-      def uncached_config
-        scope.connection_db_config.configuration_hash.with_indifferent_access
-      end
-
       def config
-        @config ||= uncached_config
+        # The result of this method must not be cached, as other methods may use
+        # it after making configuration changes and expect those changes to be
+        # present. For example, `disable_prepared_statements` expects the
+        # configuration settings to always be up to date.
+        #
+        # See the following for more information:
+        #
+        # - https://gitlab.com/gitlab-org/release/retrospectives/-/issues/39
+        # - https://gitlab.com/gitlab-com/gl-infra/production/-/issues/5238
+        scope.connection_db_config.configuration_hash.with_indifferent_access
       end
 
       def pool_size
@@ -72,7 +77,7 @@ module Gitlab
 
       # Disables prepared statements for the current database connection.
       def disable_prepared_statements
-        scope.establish_connection(uncached_config.merge(prepared_statements: false))
+        scope.establish_connection(config.merge(prepared_statements: false))
       end
 
       def read_only?

spec/lib/gitlab/database/connection_spec.rb

@@ -29,12 +29,19 @@ RSpec.describe Gitlab::Database::Connection do
     it 'returns a default pool size' do
       expect(connection.config).to include(pool: connection.default_pool_size)
     end
+
+    it 'does not cache its results' do
+      a = connection.config
+      b = connection.config
+
+      expect(a).not_to equal(b)
+    end
   end
 
   describe '#pool_size' do
     context 'when no explicit size is configured' do
       it 'returns the default pool size' do
-        expect(connection.config).to receive(:[]).with(:pool).and_return(nil)
+        expect(connection).to receive(:config).and_return({ pool: nil })
 
         expect(connection.pool_size).to eq(connection.default_pool_size)
       end
@@ -42,7 +49,7 @@ RSpec.describe Gitlab::Database::Connection do
 
     context 'when an explicit pool size is set' do
       it 'returns the pool size' do
-        expect(connection.config).to receive(:[]).with(:pool).and_return(4)
+        expect(connection).to receive(:config).and_return({ pool: 4 })
 
         expect(connection.pool_size).to eq(4)
       end