vcsserver/lib/archive_cache/lock.py

# Copyright (C) 2015-2024 RhodeCode GmbH
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License, version 3
# (only), as published by the Free Software Foundation.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.
#
# This program is dual-licensed. If you wish to learn more about the
# RhodeCode Enterprise Edition, including its added features, Support services,
# and proprietary license terms, please see https://rhodecode.com/licenses/

import redis
from .._vendor import redis_lock


class ArchiveCacheGenerationLock(Exception):
    pass


class GenerationLock:
    """
    Locking mechanism that detects if a lock is acquired

    with GenerationLock(lock_key):
        compute_archive()
    """
    lock_timeout = 7200

    def __init__(self, lock_key, url):
        self.lock_key = lock_key
        self._create_client(url)
        self.lock = self.get_lock()

    def _create_client(self, url):
        connection_pool = redis.ConnectionPool.from_url(url)
        self.writer_client = redis.StrictRedis(
            connection_pool=connection_pool
        )
        self.reader_client = self.writer_client

    def get_lock(self):
        return redis_lock.Lock(
            redis_client=self.writer_client,
            name=self.lock_key,
            expire=self.lock_timeout,
            strict=True
        )

    def __enter__(self):
        acquired = self.lock.acquire(blocking=False)
        if not acquired:
            raise ArchiveCacheGenerationLock('Failed to create a lock')

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.lock.release()