normalizer.py 文件源码

def from_yaml(cls, loader, node):
        logging.debug('{}:from_yaml(loader={})'.format(cls.__name__, loader))
        default, select, value_desc = None, list(), None
        # find value description
        for elem in node.value:
            for key, value in elem.value:
                if key.value == 'VALUE':
                    assert value_desc is None, "VALUE key already set"
                    value_desc = value
                if key.value == 'SELECT':
                    select.append(loader.construct_mapping(value))
                if key.value == 'DEFAULT':
                    assert default is None, "DEFAULT key already set"
                    default = loader.construct_object(value)
        # if VALUE key isn't given, use default VALUE key
        # format: `VALUE: !Number '{vl.value}'`
        if value_desc is None:
            value_desc = yaml.ScalarNode(tag=u'!Number', value=u'{vl.value}')
        # select collectd metric based on SELECT condition
        metrics = loader.collector.items(select)
        assert len(metrics) < 2, \
            'Wrong SELECT condition {}, selected {} metrics'.format(
            select, len(metrics))
        if len(metrics) > 0:
            item = cls.format_node(value_desc, {'vl': metrics[0],
                                   'system': loader.system})
            return loader.construct_object(item)
        # nothing has been found by SELECT condition, set to DEFAULT value.
        assert default is not None, "No metrics selected by SELECT condition" \
            " {} and DEFAULT key isn't set".format(select)
        return default