Provides a simple (top-level only) wrapper around the AWS ec2 instance metadata interface

ec2_metadata_manager.py

import requests

METADATA_URL = 'http://169.254.169.254/latest/meta-data/'


class AmiMetaDataManager:
    """
    Provides a simple wrapper around the AWS ec2 instance metadata interface
    http://docs.aws.amazon.com/AWSEC2/latest/UserGuide/ec2-instance-metadata.html
    """

    def __init__(self, url=METADATA_URL):
        self._url = url
        self._metadata_fields = self.get_metadata_fields(url)

        # creates a function for returning each metadata fieldname value
        for field in self._metadata_fields:
            def createfunc(fieldname):
                def func():
                    return self.get_field_value(fieldname)
                return func
            created_function = createfunc(field)
            setattr(self.__class__, 'get_{}'.format(field), staticmethod(created_function))

    def get_metadata_fields(self, url=METADATA_URL):
        response = requests.get(url)
        lines = response.text.split('\n')
        # available attributes are returned as a list of lines
        fields = [field.strip() for field in lines if field and not field.endswith('/')]
        return fields

    def get_field_value(self, fieldname):
        url = '{}{}'.format(self._url, fieldname)
        response = requests.get(url)
        return response.text.strip()


if __name__ == '__main__':
    import argparse
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument('-l', '--list-fields',
                        dest='list_fields',
                        action='store_true',
                        help='If given, fields will be listed')
    parser.add_argument('-f', '--field',
                        help='Get field value for given field')
    args = parser.parse_args()

    metamgr = AmiMetaDataManager()
    available_fields = metamgr.get_metadata_fields()

    if args.list_fields:
        print('Available Fields:')
        for f in available_fields:
            print('\t{}'.format(f))
    elif args.field in available_fields:
        result = metamgr.get_field_value(args.field)
        print(result)
    else:
        print('ERROR -- ({}) not in: {}'.format(args.field, ', '.join(available_fields)))