class ActiveRecord::ConnectionAdapters::ConnectionHandler

def connected?(spec_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)

already been opened.
Returns true if a connection that's accessible to this class has

def connected?(spec_name, role: ActiveRecord::Base.current_role, shard: ActiveRecord::Base.current_shard)
  pool = retrieve_connection_pool(spec_name, role: role, shard: shard)
  pool && pool.connected?
end

Instance Methods