remove_stale_cached_threads!

# File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 145
        def remove_stale_cached_threads!(cache, &block)
          stale = Set.new(cache.keys)

          Thread.list.each do |thread|
            stale.delete(thread.object_id) if thread.alive?
          end

          stale.each do |thread_id|
            clear_cache!(cache, thread_id, &block)
          end
        end