[Checkins] SVN: ZODB/trunk/s Fixed bug: The new option to drop the cache on verify didn't leave the
Jim Fulton
jim at zope.com
Tue Nov 18 20:45:12 EST 2008
Log message for revision 93122:
Fixed bug: The new option to drop the cache on verify didn't leave the
cache or the client storage in a valid state.
Also, changed the drop-cache feature to:
- Log a critical message and to
- Publish an event. Some applications might want to captre the event
and exit the process or take some drastic action when the cahe needs
to be dropped.
Changed:
U ZODB/trunk/setup.py
U ZODB/trunk/src/ZEO/ClientStorage.py
U ZODB/trunk/src/ZEO/interfaces.py
A ZODB/trunk/src/ZEO/tests/drop_cache_rather_than_verify.txt
U ZODB/trunk/src/ZEO/tests/testZEO.py
-=-
Modified: ZODB/trunk/setup.py
===================================================================
--- ZODB/trunk/setup.py 2008-11-19 01:45:09 UTC (rev 93121)
+++ ZODB/trunk/setup.py 2008-11-19 01:45:11 UTC (rev 93122)
@@ -260,13 +260,14 @@
'zdaemon',
],
install_requires = [
+ 'transaction',
+ 'zc.lockfile',
+ 'ZConfig',
+ 'zdaemon',
+ 'zope.event',
'zope.interface',
'zope.proxy',
'zope.testing',
- 'ZConfig',
- 'zdaemon',
- 'transaction',
- 'zc.lockfile',
],
zip_safe = False,
entry_points = """
Modified: ZODB/trunk/src/ZEO/ClientStorage.py
===================================================================
--- ZODB/trunk/src/ZEO/ClientStorage.py 2008-11-19 01:45:09 UTC (rev 93121)
+++ ZODB/trunk/src/ZEO/ClientStorage.py 2008-11-19 01:45:11 UTC (rev 93122)
@@ -19,7 +19,19 @@
"""
+from persistent.TimeStamp import TimeStamp
+from ZEO.auth import get_module
+from ZEO.cache import ClientCache
+from ZEO.Exceptions import ClientStorageError, ClientDisconnected, AuthError
+from ZEO import ServerStub
+from ZEO.TransactionBuffer import TransactionBuffer
+from ZEO.zrpc.client import ConnectionManager
+from ZODB.blob import rename_or_copy_blob
+from ZODB import POSException
+from ZODB import utils
+from ZODB.loglevels import BLATHER
import cPickle
+import logging
import os
import socket
import stat
@@ -28,24 +40,13 @@
import threading
import time
import types
-import logging
import weakref
-
-import zope.interface
-from ZEO import ServerStub
-from ZEO.cache import ClientCache
-from ZEO.TransactionBuffer import TransactionBuffer
-from ZEO.Exceptions import ClientStorageError, ClientDisconnected, AuthError
-from ZEO.auth import get_module
-from ZEO.zrpc.client import ConnectionManager
-
-import ZODB.interfaces
import zc.lockfile
+import ZEO.interfaces
import ZODB.BaseStorage
-from ZODB import POSException
-from ZODB import utils
-from ZODB.blob import rename_or_copy_blob
-from persistent.TimeStamp import TimeStamp
+import ZODB.interfaces
+import zope.event
+import zope.interface
logger = logging.getLogger(__name__)
@@ -112,7 +113,7 @@
def __init__(self, addr, storage='1', cache_size=20 * MB,
name='', client=None, debug=0, var=None,
- min_disconnect_poll=5, max_disconnect_poll=300,
+ min_disconnect_poll=1, max_disconnect_poll=30,
wait_for_server_on_startup=None, # deprecated alias for wait
wait=None, wait_timeout=None,
read_only=0, read_only_fallback=0,
@@ -223,12 +224,6 @@
logger.warning(
"%s ClientStorage(): debug argument is no longer used",
self.__name__)
-
- # Remember some parameters for "_setupCache"
- self._var_ = var
- self._storage_ = storage
- self._client_ = client
- self._cache_size_ = cache_size
self._drop_cache_rather_verify = drop_cache_rather_verify
@@ -357,8 +352,14 @@
else:
self.fshelper = None
- self._setupCache()
+ if client is not None:
+ dir = var or os.getcwd()
+ cache_path = os.path.join(dir, "%s-%s.zec" % (client, storage))
+ else:
+ cache_path = None
+ self._cache = self.ClientCacheClass(cache_path, size=cache_size)
+
self._rpc_mgr = self.ConnectionManagerClass(addr, self,
tmin=min_disconnect_poll,
tmax=max_disconnect_poll)
@@ -372,19 +373,6 @@
if not self._rpc_mgr.attempt_connect():
self._rpc_mgr.connect()
- def _setupCache(self):
- '''create and open the cache.'''
- # Decide whether to use non-temporary files
- storage = self._storage_
- client = self._client_
- cache_size = self._cache_size_
- if client is not None:
- dir = self._var_ or os.getcwd()
- cache_path = os.path.join(dir, "%s-%s.zec" % (client, storage))
- else:
- cache_path = None
- self._cache = self.ClientCacheClass(cache_path, size=cache_size)
-
def _wait(self, timeout=None):
if timeout is not None:
deadline = time.time() + timeout
@@ -1276,11 +1264,12 @@
self._db.invalidateCache()
if self._cache and self._drop_cache_rather_verify:
- logger.info("%s dropping cache", self.__name__)
- self._cache.close()
- self._setupCache() # creates a new cache
- self._server = server
- self._ready.set()
+ logger.critical("%s dropping stale cache", self.__name__)
+ zope.event.notify(ZEO.interfaces.CacheDroppedEvent())
+ self._cache.clear()
+ if ltid:
+ self._cache.setLastTid(ltid)
+ self.finish_verification()
return "cache dropped"
logger.info("%s Verifying cache", self.__name__)
Modified: ZODB/trunk/src/ZEO/interfaces.py
===================================================================
--- ZODB/trunk/src/ZEO/interfaces.py 2008-11-19 01:45:09 UTC (rev 93121)
+++ ZODB/trunk/src/ZEO/interfaces.py 2008-11-19 01:45:11 UTC (rev 93122)
@@ -14,6 +14,10 @@
import zope.interface
+class CacheDroppedEvent(object):
+ """A ZEO Cache file was dropped to avoid verification
+ """
+
class IServeable(zope.interface.Interface):
"""Interface provided by storages that can be served by ZEO
"""
Added: ZODB/trunk/src/ZEO/tests/drop_cache_rather_than_verify.txt
===================================================================
--- ZODB/trunk/src/ZEO/tests/drop_cache_rather_than_verify.txt (rev 0)
+++ ZODB/trunk/src/ZEO/tests/drop_cache_rather_than_verify.txt 2008-11-19 01:45:11 UTC (rev 93122)
@@ -0,0 +1,153 @@
+Avoiding cache verifification
+=============================
+
+For large databases it is common to also use very large ZEO cache
+files. If a client has beed disconnected for too long, cache verification
+might be necessary, but cache verification can be very hard on the
+storage server.
+
+ClientStorage provides an option to drop it's cache rather than doing
+verification. When this option is used, and verification would be
+necessary, ClientStorage:
+
+- Invalidates all object caches
+
+- Drops or clears it's client cache. (The end result is that the cache
+ is working but empty.)
+
+- Logs a CRITICAL message.
+
+- Publishes a ZEO.interfaces.CacheDroppedEvent event.
+
+Here's an example that shows that this is actually what happens.
+
+Start a server, create a cient to it and commit some data
+
+ >>> addr, admin = start_server(keep=1)
+ >>> import ZEO, transaction
+ >>> db = ZEO.DB(addr, drop_cache_rather_verify=True, client='cache',
+ ... name='test')
+ >>> wait_connected(db.storage)
+ >>> conn = db.open()
+ >>> conn.root()[1] = conn.root().__class__()
+ >>> conn.root()[1].x = 1
+ >>> transaction.commit()
+ >>> len(db.storage._cache)
+ 3
+
+Now, we'll stop the server and restart with a different address:
+
+ >>> stop_server(admin)
+ >>> addr2, admin = start_server(keep=1)
+
+And create another client and write some data to it:
+
+ >>> db2 = ZEO.DB(addr2)
+ >>> wait_connected(db2.storage)
+ >>> conn2 = db2.open()
+ >>> for i in range(5):
+ ... conn2.root()[1].x += 1
+ ... transaction.commit()
+ >>> db2.close()
+ >>> stop_server(admin)
+
+Now, we'll restart the server. Before we do that, we'll capture
+logging and event data:
+
+ >>> import logging, zope.testing.loggingsupport, zope.event
+ >>> handler = zope.testing.loggingsupport.InstalledHandler(
+ ... 'ZEO.ClientStorage', level=logging.ERROR)
+ >>> events = []
+ >>> zope.event.subscribers.append(events.append)
+
+Now, we'll restart the server on the original address:
+
+ >>> _, admin = start_server(zeo_conf=dict(invalidation_queue_size=1),
+ ... addr=addr, keep=1)
+ >>> wait_connected(db.storage)
+
+Now, let's verify our assertions above:
+
+- Drops or clears it's client cache. (The end result is that the cache
+ is working but empty.)
+
+ >>> len(db.storage._cache)
+ 0
+
+- Invalidates all object caches
+
+ >>> transaction.abort()
+ >>> conn.root()._p_changed
+
+- Logs a CRITICAL message.
+
+ >>> print handler
+ ZEO.ClientStorage CRITICAL
+ test dropping stale cache
+
+ >>> handler.clear()
+
+- Publishes a cache-dropped event.
+
+ >>> for e in events:
+ ... print e.__class__.__name__
+ CacheDroppedEvent
+
+ >>> del events[:]
+
+If we access the root object, it'll be loaded from the server:
+
+ >>> conn.root()[1].x
+ 6
+
+ >>> len(db.storage._cache)
+ 2
+
+Similarly, if we simply disconnect the client, and write data from
+another client:
+
+ >>> db.close()
+
+ >>> db2 = ZEO.DB(addr)
+ >>> wait_connected(db2.storage)
+ >>> conn2 = db2.open()
+ >>> for i in range(5):
+ ... conn2.root()[1].x += 1
+ ... transaction.commit()
+ >>> db2.close()
+
+ >>> db = ZEO.DB(addr, drop_cache_rather_verify=True, client='cache',
+ ... name='test')
+ >>> wait_connected(db.storage)
+
+
+- Drops or clears it's client cache. (The end result is that the cache
+ is working but empty.)
+
+ >>> len(db.storage._cache)
+ 1
+
+(When a database is created, it checks to make sure the root object is
+in the database, which is why we get 1, rather than 0 objects in the cache.)
+
+- Logs a CRITICAL message.
+
+ >>> print handler
+ ZEO.ClientStorage CRITICAL
+ test dropping stale cache
+
+ >>> handler.clear()
+
+- Publishes a cache-dropped event.
+
+ >>> for e in events:
+ ... print e.__class__.__name__
+ CacheDroppedEvent
+
+If we access the root object, it'll be loaded from the server:
+
+ >>> conn = db.open()
+ >>> conn.root()[1].x
+ 11
+
+ >>> db.close()
Property changes on: ZODB/trunk/src/ZEO/tests/drop_cache_rather_than_verify.txt
___________________________________________________________________
Added: svn:eol-style
+ native
Modified: ZODB/trunk/src/ZEO/tests/testZEO.py
===================================================================
--- ZODB/trunk/src/ZEO/tests/testZEO.py 2008-11-19 01:45:09 UTC (rev 93121)
+++ ZODB/trunk/src/ZEO/tests/testZEO.py 2008-11-19 01:45:11 UTC (rev 93122)
@@ -148,35 +148,8 @@
self.assertNotEquals(ZODB.utils.z64, storage3.lastTransaction())
storage3.close()
- def checkDropCacheRatherVerifyImplementation(self):
- # As it is quite difficult to set things up such that the verification
- # optimizations do not step in, we emulate both the cache
- # as well as the server.
- from ZODB.TimeStamp import TimeStamp
- class CacheEmulator(object):
- # the settings below would be inconsitent for a normal cache
- # but they are sufficient for our test setup
- def __len__(self): return 1 # claim not to be empty
- def contents(self): return () # do not invalidate anything
- def getLastTid(self): return
- def close(self): pass
- class ServerEmulator(object):
- def verify(*unused): pass
- def endZeoVerify(*unused): pass
- def lastTransaction(*unused): pass
- storage = self._storage
- storage._cache = cache = CacheEmulator()
- server = ServerEmulator()
- # test the standard behaviour
- self.assertEqual(storage.verify_cache(server), "full verification")
- # test the "drop cache rather verify" behaviour
- storage._drop_cache_rather_verify = True
- self.assertEqual(storage.verify_cache(server), "cache dropped")
- # verify that we got a new cache
- self.assert_(cache != storage._cache)
-
-
class ConfigurationTests(unittest.TestCase):
+
def checkDropCacheRatherVerifyConfiguration(self):
from ZODB.config import storageFromString
# the default is to do verification and not drop the cache
@@ -1118,6 +1091,7 @@
zeo.addTest(
doctest.DocFileSuite(
'zeo-fan-out.test', 'zdoptions.test',
+ 'drop_cache_rather_than_verify.txt',
setUp=forker.setUp, tearDown=zope.testing.setupstack.tearDown,
),
)
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