def state(self, metric=None, index=None, params=None):
        """
        Get a comprehensive state information of the whole cluster.
        `<http://www.elastic.co/guide/en/elasticsearch/reference/current/cluster-state.html>`_

        :arg metric: Limit the information returned to the specified metrics
        :arg index: A comma-separated list of index names; use `_all` or empty
            string to perform the operation on all indices
        :arg allow_no_indices: Whether to ignore if a wildcard indices
            expression resolves into no concrete indices. (This includes `_all`
            string or when no indices have been specified)
        :arg expand_wildcards: Whether to expand wildcard expression to concrete
            indices that are open, closed or both., default 'open', valid
            choices are: 'open', 'closed', 'none', 'all'
        :arg flat_settings: Return settings in flat format (default: false)
        :arg ignore_unavailable: Whether specified concrete indices should be
            ignored when unavailable (missing or closed)
        :arg local: Return local information, do not retrieve the state from
            master node (default: false)
        :arg master_timeout: Specify timeout for connection to master
        """
        if index and not metric:
            metric = '_all'
        return self.transport.perform_request('GET', _make_path('_cluster',
            'state', metric, index), params=params)