class ActiveRecord::ConnectionAdapters::ConnectionHandler

def initialize
  # These caches are keyed by pool_config.connection_specification_name (PoolConfig#connection_specification_name).
  @owner_to_pool_manager = Concurrent::Map.new(initial_capacity: 2)
  # Backup finalizer: if the forked child skipped Kernel#fork the early discard has not occurred
  ObjectSpace.define_finalizer self, FINALIZER
end