Set db name when creating connection with new pool size

Changelog: fixed

config/initializers/database_config.rb

@@ -20,12 +20,7 @@ Gitlab.ee do
   end
 end
 
-db_config = Gitlab::Database.main.config ||
-            Rails.application.config.database_configuration[Rails.env]
-
-ActiveRecord::Base.establish_connection(
-  db_config.merge(pool: Gitlab::Database.main.default_pool_size)
-)
+ActiveRecord::Base.establish_connection(Gitlab::Database.main.db_config_with_default_pool_size)
 
 Gitlab.ee do
   if Gitlab::Runtime.sidekiq? && Gitlab::Geo.geo_database_configured?

lib/gitlab/database/connection.rb

@@ -75,6 +75,17 @@ module Gitlab
         adapter_name.casecmp('postgresql') == 0
       end
 
+      def db_config_with_default_pool_size
+        db_config_object = scope.connection_db_config
+        config = db_config_object.configuration_hash.merge(pool: default_pool_size)
+
+        ActiveRecord::DatabaseConfigurations::HashConfig.new(
+          db_config_object.env_name,
+          db_config_object.name,
+          config
+        )
+      end
+
       # Disables prepared statements for the current database connection.
       def disable_prepared_statements
         scope.establish_connection(config.merge(prepared_statements: false))

spec/initializers/database_config_spec.rb

@@ -21,6 +21,14 @@ RSpec.describe 'Database config initializer' do
 
   let(:max_threads) { 8 }
 
+  it 'retains the correct database name for the connection' do
+    previous_db_name = Gitlab::Database.main.scope.connection.pool.db_config.name
+
+    subject
+
+    expect(Gitlab::Database.main.scope.connection.pool.db_config.name).to eq(previous_db_name)
+  end
+
   context 'when no custom headroom is specified' do
     it 'sets the pool size based on the number of worker threads' do
       old = ActiveRecord::Base.connection_db_config.pool

spec/lib/gitlab/database/connection_spec.rb

@@ -127,6 +127,20 @@ RSpec.describe Gitlab::Database::Connection do
     end
   end
 
+  describe '#db_config_with_default_pool_size' do
+    it 'returns db_config with our default pool size' do
+      allow(connection).to receive(:default_pool_size).and_return(9)
+
+      expect(connection.db_config_with_default_pool_size.pool).to eq(9)
+    end
+
+    it 'returns db_config with the correct database name' do
+      db_name = connection.scope.connection.pool.db_config.name
+
+      expect(connection.db_config_with_default_pool_size.name).to eq(db_name)
+    end
+  end
+
   describe '#disable_prepared_statements' do
     around do |example|
       original_config = ::Gitlab::Database.main.config

spec/support/shared_examples/metrics/active_record_subscriber_shared_examples.rb

 # frozen_string_literal: true
 
 RSpec.shared_examples 'store ActiveRecord info in RequestStore' do |db_role|
-  let(:db_config_name) { ::Gitlab::Database.db_config_name(ApplicationRecord.connection) }
+  let(:db_config_name) { ::Gitlab::Database.db_config_names.first }
 
   let(:expected_payload_defaults) do
     metrics =
@@ -14,13 +14,21 @@ RSpec.shared_examples 'store ActiveRecord info in RequestStore' do |db_role|
     end
   end
 
+  def transform_hash(hash, another_hash)
+    another_hash.each do |key, value|
+      raise "Unexpected key: #{key}" unless hash[key]
+    end
+
+    hash.merge(another_hash)
+  end
+
   it 'prevents db counters from leaking to the next transaction' do
     2.times do
       Gitlab::WithRequestStore.with_request_store do
         subscriber.sql(event)
 
         expected = if db_role == :primary
-                     expected_payload_defaults.merge({
+                     transform_hash(expected_payload_defaults, {
                        db_count: record_query ? 1 : 0,
                        db_write_count: record_write_query ? 1 : 0,
                        db_cached_count: record_cached_query ? 1 : 0,
@@ -36,7 +44,7 @@ RSpec.shared_examples 'store ActiveRecord info in RequestStore' do |db_role|
                        "db_primary_#{db_config_name}_wal_cached_count": record_wal_query && record_cached_query ? 1 : 0
                      })
                    elsif db_role == :replica
-                     expected_payload_defaults.merge({
+                     transform_hash(expected_payload_defaults, {
                        db_count: record_query ? 1 : 0,
                        db_write_count: record_write_query ? 1 : 0,
                        db_cached_count: record_cached_query ? 1 : 0,