caches: use safer method of purging keys from memory dict. During some concurrency tests

we detected that has_key has a race condition, and catching exception is safer.

rhodecode/lib/rc_cache/backends.py

@@ -1,199 +1,201 b''
 # -*- coding: utf-8 -*-
 
 # Copyright (C) 2015-2018 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 time
 import errno
 import logging
 
 import gevent
 
 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 lru import LRU as LRUDict
 
 
 _default_max_size = 1024
 
 log = logging.getLogger(__name__)
 
 
 class LRUMemoryBackend(memory_backend.MemoryBackend):
     pickle_values = False
 
     def __init__(self, arguments):
         max_size = arguments.pop('max_size', _default_max_size)
         callback = None
         if arguments.pop('log_max_size_reached', None):
             def evicted(key, value):
                 log.debug(
                     'LRU: evicting key `%s` due to max size %s reach', key, max_size)
             callback = evicted
 
         arguments['cache_dict'] = LRUDict(max_size, callback=callback)
         super(LRUMemoryBackend, self).__init__(arguments)
 
     def delete(self, key):
-        if self._cache.has_key(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:
-            if self._cache.has_key(key):
-                del self._cache[key]
+            self.delete(key)
 
 
 class Serializer(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 CustomLockFactory(FileLock):
 
     @memoized_property
     def _module(self):
         import fcntl
         flock_org = fcntl.flock
 
         def gevent_flock(fd, operation):
             """
             Gevent compatible flock
             """
             # set non-blocking, this will cause an exception if we cannot acquire a lock
             operation |= fcntl.LOCK_NB
             start_lock_time = time.time()
             timeout = 60 * 5  # 5min
             while True:
                 try:
                     flock_org(fd, operation)
                     # lock has been acquired
                     break
                 except (OSError, IOError) as e:
                     # raise on other errors than Resource temporarily unavailable
                     if e.errno != errno.EAGAIN:
                         raise
                     elif (time.time() - start_lock_time) > timeout:
                         # waited to much time on a lock, better fail than loop for ever
                         raise
 
                     log.debug('Failed to acquire lock, retry in 0.1')
                     gevent.sleep(0.1)
 
         fcntl.flock = gevent_flock
         return fcntl
 
 
 class FileNamespaceBackend(Serializer, file_backend.DBMBackend):
 
     def __init__(self, arguments):
         arguments['lock_factory'] = CustomLockFactory
         super(FileNamespaceBackend, self).__init__(arguments)
 
     def list_keys(self, prefix=''):
         def cond(v):
             if not prefix:
                 return True
 
             if v.startswith(prefix):
                 return True
             return False
 
         with self._dbm_file(True) as dbm:
 
             return filter(cond, dbm.keys())
 
     def get_store(self):
         return self.filename
 
     def 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 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 RedisPickleBackend(Serializer, redis_backend.RedisBackend):
     def list_keys(self, prefix=''):
         if prefix:
             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 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):
         mapping = dict(
             (k, self._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()