o2ims/service/unit_of_work.py

   1 # Copyright (C) 2021 Wind River Systems, Inc.
   2 #
   3 #  Licensed under the Apache License, Version 2.0 (the "License");
   4 #  you may not use this file except in compliance with the License.
   5 #  You may obtain a copy of the License at
   6 #
   7 #      http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 #  Unless required by applicable law or agreed to in writing, software
  10 #  distributed under the License is distributed on an "AS IS" BASIS,
  11 #  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 #  See the License for the specific language governing permissions and
  13 #  limitations under the License.
  14
  15 # pylint: disable=attribute-defined-outside-init
  16 from __future__ import annotations
  17 import abc
  18 from sqlalchemy import create_engine
  19 from sqlalchemy.orm import sessionmaker
  20 from sqlalchemy.orm.session import Session
  21
  22 from o2ims import config
  23 from o2ims.adapter import ocloud_repository
  24
  25
  26 class AbstractUnitOfWork(abc.ABC):
  27     oclouds: ocloud_repository.OcloudRepository
  28
  29     def __enter__(self):
  30         return self
  31
  32     def __exit__(self, *args):
  33         self.rollback()
  34
  35     def commit(self):
  36         self._commit()
  37
  38     def collect_new_events(self):
  39         for ocloud in self.oclouds.seen:
  40             while ocloud.events:
  41                 yield ocloud.events.pop(0)
  42
  43     @abc.abstractmethod
  44     def _commit(self):
  45         raise NotImplementedError
  46
  47     @abc.abstractmethod
  48     def rollback(self):
  49         raise NotImplementedError
  50
  51
  52 DEFAULT_SESSION_FACTORY = sessionmaker(
  53     bind=create_engine(
  54         config.get_postgres_uri(),
  55         isolation_level="REPEATABLE READ",
  56     )
  57 )
  58
  59
  60 class SqlAlchemyUnitOfWork(AbstractUnitOfWork):
  61     def __init__(self, session_factory=DEFAULT_SESSION_FACTORY):
  62         self.session_factory = session_factory
  63
  64     def __enter__(self):
  65         self.session = self.session_factory()  # type: Session
  66         self.oclouds = ocloud_repository\
  67             .OcloudSqlAlchemyRepository(self.session)
  68         return super().__enter__()
  69
  70     def __exit__(self, *args):
  71         super().__exit__(*args)
  72         self.session.close()
  73
  74     def _commit(self):
  75         self.session.commit()
  76
  77     def rollback(self):
  78         self.session.rollback()