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# Copyright 2009 Canonical Ltd. This software is licensed under the
# GNU Affero General Public License version 3 (see the file LICENSE).
"""Code to represent a single session of EC2 use."""
__metaclass__ = type
__all__ = [
'EC2SessionName',
]
from datetime import datetime, timedelta
from devscripts.ec2test.utils import (
find_datetime_string, make_datetime_string, make_random_string)
DEFAULT_LIFETIME = timedelta(hours=6)
class EC2SessionName(str):
"""A name for an EC2 session.
This is used when naming key pairs and security groups, so it's
useful to be unique. However, to aid garbage collection of old key
pairs and security groups, the name contains a common element and
an expiry timestamp. The form taken should always be:
<base-name>/<expires-timestamp>/<random-data>
None of the parts should contain forward-slashes, and the
timestamp should be acceptable input to `find_datetime_string`.
`EC2SessionName.make()` will generate a suitable name given a
suitable base name.
"""
@classmethod
def make(cls, base, expires=None):
"""Create an `EC2SessionName`.
This checks that `base` does not contain a forward-slash, and
provides some convenient functionality for `expires`:
- If `expires` is None, it defaults to now (UTC) plus
`DEFAULT_LIFETIME`.
- If `expires` is a `datetime`, it is converted to a timestamp
in the correct form.
- If `expires` is a `timedelta`, it is added to now (UTC) then
converted to a timestamp.
- Otherwise `expires` is assumed to be a string, so is checked
for the absense of forward-slashes, and that a correctly
formed timestamp can be discovered.
"""
assert '/' not in base
if expires is None:
expires = DEFAULT_LIFETIME
if isinstance(expires, timedelta):
expires = datetime.utcnow() + expires
if isinstance(expires, datetime):
expires = make_datetime_string(expires)
else:
assert '/' not in expires
assert find_datetime_string(expires) is not None
rand = make_random_string(8)
return cls("%s/%s/%s" % (base, expires, rand))
@property
def base(self):
parts = self.split('/')
if len(parts) != 3:
return None
return parts[0]
@property
def expires(self):
parts = self.split('/')
if len(parts) != 3:
return None
return find_datetime_string(parts[1])
@property
def rand(self):
parts = self.split('/')
if len(parts) != 3:
return None
return parts[2]
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