new

# File activerecord/lib/active_record/connection_adapters/pool_config.rb, line 28
      def initialize(connection_class, db_config, role, shard)
        super()
        @server_version = nil
        self.connection_descriptor = connection_class
        @db_config = db_config
        @role = role
        @shard = shard
        @pool = nil
        INSTANCES[self] = self
      end