'Return the datapoints for a metric.
:param cnxt: RPC context.
:param metric_namespace: Name of the namespace you want to see, or None
to see all.
:param metric_name: Name of the metric you want to see, or None to see
all.'

@context.request_context
def show_watch_metric(self, cnxt, metric_namespace=None, metric_name=None):

    if ((metric_namespace is not None) or (metric_name is not None)):
        LOG.error('Filtering    by    namespace/metric    not    yet    supported')
        return
    try:
        wds = watch_data.WatchData.get_all(cnxt)
        rule_names = {r.id: r.name for r in watch_rule.WatchRule.get_all(cnxt)}
    except Exception as ex:
        LOG.warning('show_metric    (all)    db    error    %s', ex)
        return
    result = [api.format_watch_data(w, rule_names) for w in wds]
    return result
