ospurge/ospurge/resources/base.py

#  Licensed under the Apache License, Version 2.0 (the "License"); you may
#  not use this file except in compliance with the License. You may obtain
#  a copy of the License at
#
#       http://www.apache.org/licenses/LICENSE-2.0
#
#  Unless required by applicable law or agreed to in writing, software
#  distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#  WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#  License for the specific language governing permissions and limitations
#  under the License.
import abc
import collections
import inspect
import logging
import threading
import time
from typing import Any
from typing import Dict
from typing import Iterable
from typing import TYPE_CHECKING

from ospurge import exceptions

if TYPE_CHECKING:  # pragma: no cover
    import argparse  # noqa: F401
    from ospurge.main import CredentialsManager  # noqa: F401
    import shade  # noqa: F401
    from typing import Optional  # noqa: F401


class MatchSignaturesMeta(type):
    def __init__(self, clsname, bases, clsdict):
        super().__init__(clsname, bases, clsdict)
        sup = super(self, self)  # type: ignore   # See python/mypy #857
        for name, value in clsdict.items():
            if name.startswith('_') or not callable(value):
                continue

            # Get the previous definition (if any) and compare the signatures
            prev_dfn = getattr(sup, name, None)
            if prev_dfn:
                prev_sig = inspect.signature(prev_dfn)
                val_sig = inspect.signature(value)
                if prev_sig != val_sig:
                    logging.warning('Signature mismatch in %s. %s != %s',
                                    value.__qualname__, prev_sig, val_sig)


class OrderedMeta(type):
    def __new__(cls, clsname, bases, clsdict):
        ordered_methods = cls.ordered_methods
        allowed_next_methods = list(ordered_methods)
        for name, value in clsdict.items():
            if name not in ordered_methods:
                continue

            if name not in allowed_next_methods:
                logging.warning(
                    "Method %s not defined at the correct location. Methods "
                    "in class %s must be defined in the following order %r",
                    value.__qualname__, clsname, ordered_methods
                )
                continue  # pragma: no cover

            _slice = slice(allowed_next_methods.index(name) + 1, None)
            allowed_next_methods = allowed_next_methods[_slice]

        # Cast to dict is required. We can't pass an OrderedDict here.
        return super().__new__(cls, clsname, bases, dict(clsdict))

    @classmethod
    def __prepare__(cls, clsname, bases):
        return collections.OrderedDict()


class CodingStyleMixin(OrderedMeta, MatchSignaturesMeta, abc.ABCMeta):
    ordered_methods = ['order', 'check_prerequisite', 'list', 'should_delete',
                       'delete', 'to_string']


class BaseServiceResource(object):
    def __init__(self) -> None:
        self.cloud = None  # type: Optional[shade.OpenStackCloud]
        self.cleanup_project_id = None  # type: Optional[str]
        self.options = None  # type: Optional[argparse.Namespace]


class ServiceResource(BaseServiceResource, metaclass=CodingStyleMixin):
    ORDER = None  # type: int

    def __init__(self, creds_manager: 'CredentialsManager') -> None:
        if self.ORDER is None:
            raise ValueError(
                'Class {}.{} must override the "ORDER" class attribute'.format(
                    self.__module__, self.__class__.__name__)  # type: ignore
            )

        self.cloud = creds_manager.cloud
        self.options = creds_manager.options
        self.cleanup_project_id = creds_manager.project_id

    @classmethod
    def order(cls) -> int:
        return cls.ORDER

    def check_prerequisite(self) -> bool:
        return True

    @abc.abstractmethod
    def list(self) -> Iterable:
        raise NotImplementedError

    def should_delete(self, resource: Dict[str, Any]) -> bool:
        project_id = resource.get('project_id', resource.get('tenant_id'))
        if project_id:
            return project_id == self.cleanup_project_id
        else:
            logging.warning("Can't determine owner of resource %s", resource)
            return True

    @abc.abstractmethod
    def delete(self, resource: Dict[str, Any]) -> None:
        raise NotImplementedError

    @staticmethod
    @abc.abstractmethod
    def to_str(resource: Dict[str, Any]) -> str:
        raise NotImplementedError

    def wait_for_check_prerequisite(self, exit: threading.Event) -> None:
        timeout = time.time() + 120
        sleep = 2
        while time.time() < timeout:
            if exit.is_set():
                raise RuntimeError(
                    "Resource manager exited because it was interrupted or "
                    "another resource manager failed"
                )
            if self.check_prerequisite():
                break
            logging.info("Waiting for check_prerequisite() in %s",
                         self.__class__.__name__)
            time.sleep(sleep)
            sleep = min(sleep * 2, 8)
        else:
            raise exceptions.TimeoutError(
                "Timeout exceeded waiting for check_prerequisite()")