vcsserver/lib/rc_cache/archive_cache/lock.py

# RhodeCode VCSServer provides access to different vcs backends via network.
# Copyright (C) 2014-2024 RhodeCode GmbH
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 3 of the License, or
# (at your option) any later version.
#
# 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 General Public License
# along with this program; if not, write to the Free Software Foundation,
# Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA

import redis
from vcsserver.lib._vendor import redis_lock

from .utils import ArchiveCacheLock


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 ArchiveCacheLock('Failed to create a lock')

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