caches: further improvements on the lock implementations

vcsserver/lib/rc_cache/backends.py

@@ -1,313 +1,316 b''
 # RhodeCode VCSServer provides access to different vcs backends via network.
 # Copyright (C) 2014-2020 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 time
 import errno
 import logging
 
 import msgpack
 import redis
 
 from dogpile.cache.api import CachedValue
 from dogpile.cache.backends import memory as memory_backend
 from dogpile.cache.backends import file as file_backend
 from dogpile.cache.backends import redis as redis_backend
 from dogpile.cache.backends.file import NO_VALUE, compat, FileLock
 from dogpile.cache.util import memoized_property
 
 from pyramid.settings import asbool
 
 from vcsserver.lib.memory_lru_dict import LRUDict, LRUDictDebug
 
 
 _default_max_size = 1024
 
 log = logging.getLogger(__name__)
 
 
 class LRUMemoryBackend(memory_backend.MemoryBackend):
     key_prefix = 'lru_mem_backend'
     pickle_values = False
 
     def __init__(self, arguments):
         max_size = arguments.pop('max_size', _default_max_size)
 
         LRUDictClass = LRUDict
         if arguments.pop('log_key_count', None):
             LRUDictClass = LRUDictDebug
 
         arguments['cache_dict'] = LRUDictClass(max_size)
         super(LRUMemoryBackend, self).__init__(arguments)
 
     def delete(self, key):
         try:
             del self._cache[key]
         except KeyError:
             # we don't care if key isn't there at deletion
             pass
 
     def delete_multi(self, keys):
         for key in keys:
             self.delete(key)
 
 
 class PickleSerializer(object):
 
     def _dumps(self, value, safe=False):
         try:
             return compat.pickle.dumps(value)
         except Exception:
             if safe:
                 return NO_VALUE
             else:
                 raise
 
     def _loads(self, value, safe=True):
         try:
             return compat.pickle.loads(value)
         except Exception:
             if safe:
                 return NO_VALUE
             else:
                 raise
 
 
 class MsgPackSerializer(object):
 
     def _dumps(self, value, safe=False):
         try:
             return msgpack.packb(value)
         except Exception:
             if safe:
                 return NO_VALUE
             else:
                 raise
 
     def _loads(self, value, safe=True):
         """
         pickle maintained the `CachedValue` wrapper of the tuple
         msgpack does not, so it must be added back in.
        """
         try:
             value = msgpack.unpackb(value, use_list=False)
             return CachedValue(*value)
         except Exception:
             if safe:
                 return NO_VALUE
             else:
                 raise
 
 
 import fcntl
 flock_org = fcntl.flock
 
 
 class CustomLockFactory(FileLock):
 
     pass
 
 
 class FileNamespaceBackend(PickleSerializer, file_backend.DBMBackend):
     key_prefix = 'file_backend'
 
     def __init__(self, arguments):
         arguments['lock_factory'] = CustomLockFactory
         db_file = arguments.get('filename')
 
         log.debug('initialing %s DB in %s', self.__class__.__name__, db_file)
         try:
             super(FileNamespaceBackend, self).__init__(arguments)
         except Exception:
             log.error('Failed to initialize db at: %s', db_file)
             raise
 
     def __repr__(self):
         return '{} `{}`'.format(self.__class__, self.filename)
 
     def list_keys(self, prefix=''):
         prefix = '{}:{}'.format(self.key_prefix, prefix)
 
         def cond(v):
             if not prefix:
                 return True
 
             if v.startswith(prefix):
                 return True
             return False
 
         with self._dbm_file(True) as dbm:
             try:
                 return filter(cond, dbm.keys())
             except Exception:
                 log.error('Failed to fetch DBM keys from DB: %s', self.get_store())
                 raise
 
     def get_store(self):
         return self.filename
 
     def _dbm_get(self, key):
         with self._dbm_file(False) as dbm:
             if hasattr(dbm, 'get'):
                 value = dbm.get(key, NO_VALUE)
             else:
                 # gdbm objects lack a .get method
                 try:
                     value = dbm[key]
                 except KeyError:
                     value = NO_VALUE
             if value is not NO_VALUE:
                 value = self._loads(value)
             return value
 
     def get(self, key):
         try:
             return self._dbm_get(key)
         except Exception:
             log.error('Failed to fetch DBM key %s from DB: %s', key, self.get_store())
             raise
 
     def set(self, key, value):
         with self._dbm_file(True) as dbm:
             dbm[key] = self._dumps(value)
 
     def set_multi(self, mapping):
         with self._dbm_file(True) as dbm:
             for key, value in mapping.items():
                 dbm[key] = self._dumps(value)
 
 
 class BaseRedisBackend(redis_backend.RedisBackend):
     key_prefix = ''
 
     def __init__(self, arguments):
         super(BaseRedisBackend, self).__init__(arguments)
         self._lock_timeout = self.lock_timeout
         self._lock_auto_renewal = asbool(arguments.pop("lock_auto_renewal", True))
 
         if self._lock_auto_renewal and not self._lock_timeout:
             # set default timeout for auto_renewal
             self._lock_timeout = 30
 
     def _create_client(self):
         args = {}
 
         if self.url is not None:
             args.update(url=self.url)
 
         else:
             args.update(
                 host=self.host, password=self.password,
                 port=self.port, db=self.db
             )
 
         connection_pool = redis.ConnectionPool(**args)
 
         return redis.StrictRedis(connection_pool=connection_pool)
 
     def list_keys(self, prefix=''):
         prefix = '{}:{}*'.format(self.key_prefix, prefix)
         return self.client.keys(prefix)
 
     def get_store(self):
         return self.client.connection_pool
 
     def get(self, key):
         value = self.client.get(key)
         if value is None:
             return NO_VALUE
         return self._loads(value)
 
     def get_multi(self, keys):
         if not keys:
             return []
         values = self.client.mget(keys)
         loads = self._loads
         return [
             loads(v) if v is not None else NO_VALUE
             for v in values]
 
     def set(self, key, value):
         if self.redis_expiration_time:
             self.client.setex(key, self.redis_expiration_time,
                               self._dumps(value))
         else:
             self.client.set(key, self._dumps(value))
 
     def set_multi(self, mapping):
         dumps = self._dumps
         mapping = dict(
             (k, dumps(v))
             for k, v in mapping.items()
         )
 
         if not self.redis_expiration_time:
             self.client.mset(mapping)
         else:
             pipe = self.client.pipeline()
             for key, value in mapping.items():
                 pipe.setex(key, self.redis_expiration_time, value)
             pipe.execute()
 
     def get_mutex(self, key):
         if self.distributed_lock:
             lock_key = redis_backend.u('_lock_{0}').format(key)
             log.debug('Trying to acquire Redis lock for key %s', lock_key)
             return get_mutex_lock(self.client, lock_key, self._lock_timeout,
                                   auto_renewal=self._lock_auto_renewal)
         else:
             return None
 
 
 class RedisPickleBackend(PickleSerializer, BaseRedisBackend):
     key_prefix = 'redis_pickle_backend'
     pass
 
 
 class RedisMsgPackBackend(MsgPackSerializer, BaseRedisBackend):
     key_prefix = 'redis_msgpack_backend'
     pass
 
 
 def get_mutex_lock(client, lock_key, lock_timeout, auto_renewal=False):
     import redis_lock
 
     class _RedisLockWrapper(object):
         """LockWrapper for redis_lock"""
 
-        def __init__(self):
-            pass
-
-        @property
-        def lock(self):
+        @classmethod
+        def get_lock(cls):
             return redis_lock.Lock(
                 redis_client=client,
                 name=lock_key,
                 expire=lock_timeout,
                 auto_renewal=auto_renewal,
                 strict=True,
             )
 
+        def __init__(self):
+            self.lock = self.get_lock()
+
         def acquire(self, wait=True):
+            try:
             return self.lock.acquire(wait)
+            except redis_lock.AlreadyAquited:
+                return False
 
         def release(self):
             try:
                 self.lock.release()
             except redis_lock.NotAcquired:
                 pass
 
     return _RedisLockWrapper()