checkout_for_exclusive_access

# File activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb, line 1096
        def checkout_for_exclusive_access(checkout_timeout)
          checkout(checkout_timeout)
        rescue ConnectionTimeoutError
          # this block can't be easily moved into attempt_to_checkout_all_existing_connections's
          # rescue block, because doing so would put it outside of synchronize section, without
          # being in a critical section thread_report might become inaccurate
          msg = +"could not obtain ownership of all database connections in #{checkout_timeout} seconds"

          thread_report = []
          @connections.each do |conn|
            unless conn.owner == ActiveSupport::IsolatedExecutionState.context
              thread_report << "#{conn} is owned by #{conn.owner}"
            end
          end

          msg << " (#{thread_report.join(', ')})" if thread_report.any?

          raise ExclusiveConnectionTimeoutError.new(msg, connection_pool: self)
        end