Rewrite storage cache of client

- Stop using a list of (in)validated tid (hence removal of RevisionIndex),
  because it can't work in all cases and would even cause memory leaks.
  For example, this bug could lead to ConflictError with a single client.
  Fixit it also requires that database backends always return the next serial.
- Several performance improvements. The most important one is when the latest
  version of an object is cached: it inherits the access counter of the
  previous one (for the same oid), which gets in turn its counter reset.
- Do not waste CPU evaluating the real size taken by an entry in memory.
  Just use 'len' on the value (which is always a pickle data, i.e. a string).

git-svn-id: https://svn.erp5.org/repos/neo/trunk@2711 71dcc9de-d417-0410-9af5-da40c76e7ee4

neo/client/app.py

@@ -42,12 +42,11 @@ from neo.client.handlers import storage, master
 from neo.lib.dispatcher import Dispatcher, ForgottenPacket
 from neo.client.poll import ThreadedPoll, psThreadedPoll
 from neo.client.iterator import Iterator
-from neo.client.mq import MQ
+from neo.client.cache import ClientCache
 from neo.client.pool import ConnectionPool
 from neo.lib.util import u64, parseMasterList
 from neo.lib.profiling import profiler_decorator, PROFILING_ENABLED
 from neo.lib.debug import register as registerLiveDebugger
-from neo.client.mq_index import RevisionIndex
 from neo.client.container import ThreadContainer, TransactionContainer
 
 if PROFILING_ENABLED:
@@ -93,9 +92,7 @@ class Application(object):
 
         # no self-assigned UUID, primary master will supply us one
         self.uuid = None
-        self.mq_cache = MQ()
-        self.cache_revision_index = RevisionIndex()
-        self.mq_cache.addIndex(self.cache_revision_index)
+        self._cache = ClientCache()
         self.new_oid_list = []
         self.last_oid = '\0' * 8
         self.storage_event_handler = storage.StorageEventHandler(self)
@@ -432,20 +429,17 @@ class Application(object):
 
         self._load_lock_acquire()
         try:
-            try:
-                return self._loadFromCache(oid, serial, tid)
-            except KeyError:
-                pass
-            data, start_serial, end_serial = self._loadFromStorage(oid, serial,
-                tid)
+            result = self._loadFromCache(oid, serial, tid)
+            if not result:
+                result = self._loadFromStorage(oid, serial, tid)
                 self._cache_lock_acquire()
                 try:
-                self.mq_cache[(oid, start_serial)] = data, end_serial
+                    self._cache.store(oid, *result)
                 finally:
                     self._cache_lock_release()
-            if data == '':
+                if result[0] == '':
                     raise NEOStorageCreationUndoneError(dump(oid))
-            return data, start_serial, end_serial
+            return result
         finally:
             self._load_lock_release()
 
@@ -479,24 +473,17 @@ class Application(object):
         return data, tid, next_tid
 
     @profiler_decorator
-    def _loadFromCache(self, oid, at_tid, before_tid):
+    def _loadFromCache(self, oid, at_tid=None, before_tid=None):
         """
-        Load from local cache, raising KeyError if not found.
+        Load from local cache, return None if not found.
         """
         self._cache_lock_acquire()
         try:
-            if at_tid is not None:
-                tid = at_tid
-            elif before_tid is not None:
-                tid = self.cache_revision_index.getSerialBefore(oid,
-                    before_tid)
-            else:
-                tid = self.cache_revision_index.getLatestSerial(oid)
-            if tid is None:
-                raise KeyError
-            # Raises KeyError on miss
-            data, next_tid = self.mq_cache[(oid, tid)]
-            return (data, tid, next_tid)
+            if at_tid:
+                result = self._cache.load(oid, at_tid + '*')
+                assert not result or result[1] == at_tid
+                return result
+            return self._cache.load(oid, before_tid)
         finally:
             self._cache_lock_release()
 
@@ -808,14 +795,7 @@ class Application(object):
             # Update cache
             self._cache_lock_acquire()
             try:
-                mq_cache = self.mq_cache
-                update = mq_cache.update
-                def updateNextSerial(value):
-                    data, next_tid = value
-                    assert next_tid is None, (dump(oid), dump(base_tid),
-                        dump(next_tid))
-                    return (data, tid)
-                get_baseTID = txn_context['object_base_serial_dict'].get
+                cache = self._cache
                 for oid, data in txn_context['data_dict'].iteritems():
                     if data is None:
                         # this is just a remain of
@@ -823,16 +803,10 @@ class Application(object):
                         # was modified).
                         continue
                     # Update ex-latest value in cache
-                    base_tid = get_baseTID(oid)
-                    try:
-                        update((oid, base_tid), updateNextSerial)
-                    except KeyError:
-                        pass
-                    if data == '':
-                        self.cache_revision_index.invalidate([oid], tid)
-                    else:
+                    cache.invalidate(oid, tid)
+                    if data:
                         # Store in cache with no next_tid
-                        mq_cache[(oid, tid)] = (data, None)
+                        cache.store(oid, data, tid, None)
             finally:
                 self._cache_lock_release()
             txn_container.delete(transaction)
@@ -1105,7 +1079,7 @@ class Application(object):
         # by a pack), so don't bother invalidating on other clients.
         self._cache_lock_acquire()
         try:
-            self.mq_cache.clear()
+            self._cache.clear()
         finally:
             self._cache_lock_release()
 

neo/client/handlers/master.py

@@ -121,11 +121,12 @@ class PrimaryNotificationsHandler(BaseHandler):
         app = self.app
         app._cache_lock_acquire()
         try:
-            # ZODB required a dict with oid as key, so create it
-            app.cache_revision_index.invalidate(oid_list, tid)
+            invalidate = app._cache.invalidate
+            for oid in oid_list:
+                invalidate(oid, tid)
             db = app.getDB()
             if db is not None:
-                db.invalidate(tid, dict.fromkeys(oid_list, tid))
+                db.invalidate(tid, oid_list)
         finally:
             app._cache_lock_release()
 

neo/client/mq_index.py

-#
-# Copyright (C) 2010-2011  Nexedi SA
-#
-# 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 2
-# 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.
-from neo.client.mq import MQIndex
-
-class RevisionIndex(MQIndex):
-    """
-    This cache index allows accessing a specific revision of a cached object.
-    It requires cache key to be a 2-tuple, composed of oid and revision.
-
-    Note: it is expected that rather few revisions are held in cache, with few
-    lookups for old revisions, so they are held in a simple sorted list
-    Note2: all methods here must be called with cache lock acquired.
-    """
-    def __init__(self):
-        # key: oid
-        # value: tid list, from highest to lowest
-        self._oid_dict = {}
-        # key: oid
-        # value: tid list, from lowest to highest
-        self._invalidated = {}
-
-    def clear(self):
-        self._oid_dict.clear()
-        self._invalidated.clear()
-
-    def remove(self, key):
-        oid_dict = self._oid_dict
-        oid, tid = key
-        tid_list = oid_dict[oid]
-        tid_list.remove(tid)
-        if not tid_list:
-            # No more serial known for this object, drop entirely
-            del oid_dict[oid]
-            self._invalidated.pop(oid, None)
-
-    def add(self, key):
-        oid_dict = self._oid_dict
-        oid, tid = key
-        try:
-            serial_list = oid_dict[oid]
-        except KeyError:
-            serial_list = oid_dict[oid] = []
-        else:
-            assert tid not in serial_list
-        if not(serial_list) or tid > serial_list[0]:
-            serial_list.insert(0, tid)
-        else:
-            serial_list.insert(0, tid)
-            serial_list.sort(reverse=True)
-        invalidated = self._invalidated
-        try:
-            tid_list = invalidated[oid]
-        except KeyError:
-            pass
-        else:
-            try:
-                tid_list.remove(tid)
-            except ValueError:
-                pass
-            else:
-                if not tid_list:
-                    del invalidated[oid]
-
-    def invalidate(self, oid_list, tid):
-        """
-        Mark object invalidated by given transaction.
-        Must be called with increasing TID values (which is standard for
-        ZODB).
-        """
-        invalidated = self._invalidated
-        oid_dict = self._oid_dict
-        for oid in (x for x in oid_list if x in oid_dict):
-            try:
-                tid_list = invalidated[oid]
-            except KeyError:
-                tid_list = invalidated[oid] = []
-            assert not tid_list or tid > tid_list[-1], (dump(oid), dump(tid),
-                dump(tid_list[-1]))
-            tid_list.append(tid)
-
-    def getSerialBefore(self, oid, tid):
-        """
-        Get the first tid in cache which value is lower that given tid.
-        """
-        # WARNING: return-intensive to save on indentation
-        oid_list = self._oid_dict.get(oid)
-        if oid_list is None:
-            # Unknown oid
-            return None
-        for result in oid_list:
-            if result < tid:
-                # Candidate found
-                break
-        else:
-            # No candidate in cache.
-            return None
-        # Check if there is a chance that an intermediate revision would
-        # exist, while missing from cache.
-        try:
-            inv_tid_list = self._invalidated[oid]
-        except KeyError:
-            return result
-        # Remember: inv_tid_list is sorted in ascending order.
-        for inv_tid in inv_tid_list:
-            if tid < inv_tid:
-                # We don't care about invalidations past requested TID.
-                break
-            elif result < inv_tid < tid:
-                # An invalidation was received between candidate revision,
-                # and before requested TID: there is a matching revision we
-                # don't know of, so we cannot answer.
-                return None
-        return result
-
-    def getLatestSerial(self, oid):
-        """
-        Get the latest tid for given object.
-        """
-        result = self._oid_dict.get(oid)
-        if result is not None:
-            result = result[0]
-            try:
-                tid_list = self._invalidated[oid]
-            except KeyError:
-                pass
-            else:
-                if result < tid_list[-1]:
-                    # An invalidation happened from a transaction later than
-                    # our most recent view of this object, so we cannot answer.
-                    result = None
-        return result
-
-    def getSerialList(self, oid):
-        """
-        Get the list of all serials cache knows about for given object.
-        """
-        return self._oid_dict.get(oid, [])[:]
-

neo/storage/database/btree.py

@@ -275,37 +275,22 @@ class BTreeDatabaseManager(DatabaseManager):
 
     def _getObject(self, oid, tid=None, before_tid=None):
         tserial = self._obj.get(oid)
-        if tserial is None:
-            result = None
-        else:
+        if tserial is not None:
             if tid is None:
-                if before_tid is None:
                 try:
+                    if before_tid is None:
                         tid = tserial.maxKey()
-                    except ValueError:
-                        tid = None
                     else:
-                    before_tid -= 1
-                    try:
-                        tid = tserial.maxKey(before_tid)
+                        tid = tserial.maxKey(before_tid - 1)
                 except ValueError:
-                        tid = None
-            if tid is None:
-                result = None
-            else:
-                result = tserial.get(tid, None)
+                    return
+            result = tserial.get(tid)
             if result:
-                compression, checksum, data, value_serial = result
-                if before_tid is None:
-                    next_serial = None
-                else:
                 try:
                     next_serial = tserial.minKey(tid + 1)
                 except ValueError:
                     next_serial = None
-                result = (tid, next_serial, compression, checksum, data,
-                    value_serial)
-        return result
+                return (tid, next_serial) + result
 
     def doSetPartitionTable(self, ptid, cell_list, reset):
         pt = self._pt

neo/storage/database/manager.py

@@ -255,6 +255,8 @@ class DatabaseManager(object):
         else:
             serial, next_serial, compression, checksum, data, data_serial = \
                 result
+            assert before_tid is None or next_serial is None or \
+                   before_tid <= next_serial
             if data is None and resolve_data:
                 try:
                     _, compression, checksum, data = self._getObjectData(oid,

neo/storage/database/mysqldb.py

@@ -335,50 +335,30 @@ class MySQLDatabaseManager(DatabaseManager):
     def _getObject(self, oid, tid=None, before_tid=None):
         q = self.query
         partition = self._getPartition(oid)
-        if tid is not None:
-            r = q("""SELECT serial, compression, checksum, value, value_serial
-                        FROM obj
-                        WHERE partition = %d AND oid = %d AND serial = %d""" \
-                    % (partition, oid, tid))
-            try:
-                serial, compression, checksum, data, value_serial = r[0]
-                next_serial = None
-            except IndexError:
-                return None
-        elif before_tid is not None:
-            r = q("""SELECT serial, compression, checksum, value, value_serial
+        sql = """SELECT serial, compression, checksum, value, value_serial
                     FROM obj
                     WHERE partition = %d
-                        AND oid = %d AND serial < %d
-                        ORDER BY serial DESC LIMIT 1""" \
-                    % (partition, oid, before_tid))
+                    AND oid = %d""" % (partition, oid)
+        if tid is not None:
+            sql += ' AND serial = %d' % tid
+        elif before_tid is not None:
+            sql += ' AND serial < %d ORDER BY serial DESC LIMIT 1' % before_tid
+        else:
+            # XXX I want to express "HAVING serial = MAX(serial)", but
+            # MySQL does not use an index for a HAVING clause!
+            sql += ' ORDER BY serial DESC LIMIT 1'
+        r = q(sql)
         try:
             serial, compression, checksum, data, value_serial = r[0]
         except IndexError:
             return None
         r = q("""SELECT serial FROM obj_short
-                        WHERE partition = %d
-                        AND oid = %d AND serial >= %d
-                        ORDER BY serial LIMIT 1""" \
-                    % (partition, oid, before_tid))
+                    WHERE partition = %d AND oid = %d AND serial > %d
+                    ORDER BY serial LIMIT 1""" % (partition, oid, serial))
         try:
             next_serial = r[0][0]
         except IndexError:
             next_serial = None
-        else:
-            # XXX I want to express "HAVING serial = MAX(serial)", but
-            # MySQL does not use an index for a HAVING clause!
-            r = q("""SELECT serial, compression, checksum, value, value_serial
-                        FROM obj
-                        WHERE partition = %d AND oid = %d
-                        ORDER BY serial DESC LIMIT 1""" \
-                    % (partition, oid))
-            try:
-                serial, compression, checksum, data, value_serial = r[0]
-                next_serial = None
-            except IndexError:
-                return None
-
         return serial, next_serial, compression, checksum, data, value_serial
 
     def doSetPartitionTable(self, ptid, cell_list, reset):