* Use weakref's of DBCursor objects for the iterator cursors to avoid a
memory leak that would've occurred for all iterators that were
destroyed before having iterated until they raised StopIteration.
* Simplify some code.
* Add new test cases to check for the memleak and ensure that mixing
iteration with modification of the values for existing keys works.
diff --git a/Lib/bsddb/__init__.py b/Lib/bsddb/__init__.py
index 778ad29..99499c5 100644
--- a/Lib/bsddb/__init__.py
+++ b/Lib/bsddb/__init__.py
@@ -67,77 +67,76 @@
if sys.version >= '2.3':
exec """
import UserDict
+from weakref import ref
class _iter_mixin(UserDict.DictMixin):
+ def _make_iter_cursor(self):
+ cur = self.db.cursor()
+ key = id(cur)
+ self._cursor_refs[key] = ref(cur, self._gen_cref_cleaner(key))
+ return cur
+
+ def _gen_cref_cleaner(self, key):
+ # use generate the function for the weakref callback here
+ # to ensure that we do not hold a strict reference to cur
+ # in the callback.
+ return lambda ref: self._cursor_refs.pop(key, None)
+
def __iter__(self):
try:
- cur = self.db.cursor()
- self._iter_cursors[str(cur)] = cur
+ cur = self._make_iter_cursor()
+
+ # FIXME-20031102-greg: race condition. cursor could
+ # be closed by another thread before this call.
# since we're only returning keys, we call the cursor
# methods with flags=0, dlen=0, dofs=0
- curkey = cur.first(0,0,0)[0]
- yield curkey
+ key = cur.first(0,0,0)[0]
+ yield key
next = cur.next
while 1:
try:
- curkey = next(0,0,0)[0]
- yield curkey
+ key = next(0,0,0)[0]
+ yield key
except _bsddb.DBCursorClosedError:
- # our cursor object was closed since we last yielded
- # create a new one and attempt to reposition to the
- # right place
- cur = self.db.cursor()
- self._iter_cursors[str(cur)] = cur
+ cur = self._make_iter_cursor()
# FIXME-20031101-greg: race condition. cursor could
- # be closed by another thread before this set call.
- try:
- cur.set(curkey,0,0,0)
- except _bsddb.DBCursorClosedError:
- # halt iteration on race condition...
- raise _bsddb.DBNotFoundError
+ # be closed by another thread before this call.
+ cur.set(key,0,0,0)
next = cur.next
except _bsddb.DBNotFoundError:
- try:
- del self._iter_cursors[str(cur)]
- except KeyError:
- pass
+ return
+ except _bsddb.DBCursorClosedError:
+ # the database was modified during iteration. abort.
return
def iteritems(self):
try:
- cur = self.db.cursor()
- self._iter_cursors[str(cur)] = cur
+ cur = self._make_iter_cursor()
+
+ # FIXME-20031102-greg: race condition. cursor could
+ # be closed by another thread before this call.
kv = cur.first()
- curkey = kv[0]
+ key = kv[0]
yield kv
next = cur.next
while 1:
try:
kv = next()
- curkey = kv[0]
+ key = kv[0]
yield kv
except _bsddb.DBCursorClosedError:
- # our cursor object was closed since we last yielded
- # create a new one and attempt to reposition to the
- # right place
- cur = self.db.cursor()
- self._iter_cursors[str(cur)] = cur
+ cur = self._make_iter_cursor()
# FIXME-20031101-greg: race condition. cursor could
- # be closed by another thread before this set call.
- try:
- cur.set(curkey,0,0,0)
- except _bsddb.DBCursorClosedError:
- # halt iteration on race condition...
- raise _bsddb.DBNotFoundError
+ # be closed by another thread before this call.
+ cur.set(key,0,0,0)
next = cur.next
except _bsddb.DBNotFoundError:
- try:
- del self._iter_cursors[str(cur)]
- except KeyError:
- pass
+ return
+ except _bsddb.DBCursorClosedError:
+ # the database was modified during iteration. abort.
return
"""
else:
@@ -159,7 +158,7 @@
# thread while doing a put or delete in another thread. The
# reason is that _checkCursor and _closeCursors are not atomic
# operations. Doing our own locking around self.dbc,
- # self.saved_dbc_key and self._iter_cursors could prevent this.
+ # self.saved_dbc_key and self._cursor_refs could prevent this.
# TODO: A test case demonstrating the problem needs to be written.
# self.dbc is a DBCursor object used to implement the
@@ -169,15 +168,11 @@
# a collection of all DBCursor objects currently allocated
# by the _iter_mixin interface.
- self._iter_cursors = {}
-
+ self._cursor_refs = {}
def __del__(self):
self.close()
- def _get_dbc(self):
- return self.dbc
-
def _checkCursor(self):
if self.dbc is None:
self.dbc = self.db.cursor()
@@ -197,7 +192,10 @@
self.saved_dbc_key = c.current(0,0,0)[0]
c.close()
del c
- map(lambda c: c.close(), self._iter_cursors.values())
+ for cref in self._cursor_refs.values():
+ c = cref()
+ if c is not None:
+ c.close()
def _checkOpen(self):
if self.db is None:
diff --git a/Lib/test/test_bsddb.py b/Lib/test/test_bsddb.py
index ff8c355..1ec4801 100755
--- a/Lib/test/test_bsddb.py
+++ b/Lib/test/test_bsddb.py
@@ -3,6 +3,7 @@
Adapted to unittest format and expanded scope by Raymond Hettinger
"""
import os, sys
+import copy
import bsddb
import dbhash # Just so we know it's imported
import unittest
@@ -64,6 +65,56 @@
self.assertSetEquals(d.itervalues(), f.itervalues())
self.assertSetEquals(d.iteritems(), f.iteritems())
+ def test_iter_while_modifying_values(self):
+ if not hasattr(self.f, '__iter__'):
+ return
+
+ di = iter(self.d)
+ while 1:
+ try:
+ key = di.next()
+ self.d[key] = 'modified '+key
+ except StopIteration:
+ break
+
+ # it should behave the same as a dict. modifying values
+ # of existing keys should not break iteration. (adding
+ # or removing keys should)
+ fi = iter(self.f)
+ while 1:
+ try:
+ key = fi.next()
+ self.f[key] = 'modified '+key
+ except StopIteration:
+ break
+
+ self.test_mapping_iteration_methods()
+
+ def test_iteritems_while_modifying_values(self):
+ if not hasattr(self.f, 'iteritems'):
+ return
+
+ di = self.d.iteritems()
+ while 1:
+ try:
+ k, v = di.next()
+ self.d[k] = 'modified '+v
+ except StopIteration:
+ break
+
+ # it should behave the same as a dict. modifying values
+ # of existing keys should not break iteration. (adding
+ # or removing keys should)
+ fi = self.f.iteritems()
+ while 1:
+ try:
+ k, v = fi.next()
+ self.f[k] = 'modified '+v
+ except StopIteration:
+ break
+
+ self.test_mapping_iteration_methods()
+
def test_first_next_looping(self):
items = [self.f.first()]
for i in xrange(1, len(self.f)):
@@ -111,15 +162,16 @@
# the cursor's read lock will deadlock the write lock request..
# test the iterator interface (if present)
- if hasattr(self, 'iteritems'):
+ if hasattr(self.f, 'iteritems'):
if debug: print "D"
- k,v = self.f.iteritems()
+ i = self.f.iteritems()
+ k,v = i.next()
if debug: print "E"
self.f[k] = "please don't deadlock"
if debug: print "F"
while 1:
try:
- k,v = self.f.iteritems()
+ k,v = i.next()
except StopIteration:
break
if debug: print "F2"
@@ -144,6 +196,27 @@
self.f[k] = "be gone with ye deadlocks"
self.assert_(self.f[k], "be gone with ye deadlocks")
+ def test_for_cursor_memleak(self):
+ if not hasattr(self.f, 'iteritems'):
+ return
+
+ # do the bsddb._DBWithCursor _iter_mixin internals leak cursors?
+ nc1 = len(self.f._cursor_refs)
+ # create iterator
+ i = self.f.iteritems()
+ nc2 = len(self.f._cursor_refs)
+ # use the iterator (should run to the first yeild, creating the cursor)
+ k, v = i.next()
+ nc3 = len(self.f._cursor_refs)
+ # destroy the iterator; this should cause the weakref callback
+ # to remove the cursor object from self.f._cursor_refs
+ del i
+ nc4 = len(self.f._cursor_refs)
+
+ self.assertEqual(nc1, nc2)
+ self.assertEqual(nc1, nc4)
+ self.assert_(nc3 == nc1+1)
+
def test_popitem(self):
k, v = self.f.popitem()
self.assert_(k in self.d)