Hello all,
Attached you can find the code for a preliminary ZODB storage manager
which is designed to take adventage of the reiserfs filesystem
(http://devlinux.com/namesys). While it is usable on other filesystems
too, the performance will decrease as the number of objects in your
database increases.
Comments:
1. This is as alpha as it can be. While it is usable to do some testing on
a spare Zope, you must be insane to even try to use this on a production
system.
2. A generic DirectoryStorage is comming soon, with the diference being
splitting files by directory (and, of course, being slower than the
reiserfs version).
3. As you can see in the source, I/O errors in critical points can corrupt
the storage.
4. It currently does not support versioning and undo. I'm working first on
getting it stable and fast, and then add these features.
Feedback is not only welcome, but wanted :)
-Petru
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##############################################################################
# To-do list:
# Critical:
# - Most I/O operations are not atomic. This means that I/O errors (and, for
# that matter, any exceptions occured in _finish) leave the storage in an
# undefined state
#
# Not critical:
# - Performance tuning -- add caches where apropiate
# - make sure locking is ok
# - provide directory splitting to enable use on non-reiser filesystems
#
# ... and probably many others
"""ReiserFS storage"""
__version__ = "0.01"
from BaseStorage import BaseStorage
import POSException
import os, struct, stat, operator
from posix import fsync
def oid2str(oid):
return "%02X"*8 % struct.unpack("!8B", oid)
class ReiserStorage(BaseStorage):
def __init__(self, dirname):
if dirname[-1] != '/':
dirname = dirname + '/'
BaseStorage.__init__(self, dirname)
self._oid_dir = dirname + 'oid/'
self._tindex = []
self._oid = '\0\0\0\0\0\0\0\0'
try:
f = open(dirname+'last_oid', 'rt')
self._oid = f.read()
f.close()
except:
pass
self.lof = open(dirname+'last_oid', 'wt')
def __len__(self):
print '__len__'
return len(os.listdir(self._oid_dir))
def getSize(self):
print 'getSize'
files = os.listdir(self._oid_dir)
files = map(lambda x,d=self._oid_dir: d+x, files)
sizes = map(lambda x: os.stat(x)[stat.ST_SIZE], files)
return reduce(operator.add, sizes)
def load(self, oid, version):
self._lock_acquire()
try:
f = open(self._oid_dir+oid2str(oid), 'rb')
p = f.read()
f.close()
return p[8:], p[:8]
finally:
self._lock_release()
def store(self, oid, serial, data, version, transaction):
if transaction is not self._transaction:
raise POSException.StorageTransactionError(self, transaction)
if version:
raise POSException.Unsupported, "Versions aren't supported"
self._lock_acquire()
try:
fname = self._oid_dir+oid2str(oid)
if os.path.exists(fname):
try:
f = open(fname, 'rb')
if serial != f.read(8):
raise POSException.ConflictError
f.close()
except IOError:
raise POSException.StorageSystemError, 'I/O
error while checking for conflicts'
serial = self._serial
self._tindex.append((oid, serial+data))
finally:
self._lock_release()
return serial
def _begin(self, tid, u, d, e):
pass
def _clear_temp(self):
self._tindex = []
def _finish(self, tid, user, desc, ext):
try:
for oid, data in self._tindex:
f = open(self._oid_dir+oid2str(oid), 'wb')
f.write(data)
fsync(f.fileno())
f.close()
self.lof.seek(0)
self.lof.write(self._oid)
fsync(self.lof.fileno())
except:
raise POSException.TransactionError, 'I/O error commiting
transaction -- your storage is likely corrupt'
def pack(self, t, referencesf):
maxoid = oid2str(self._oid)
rootl = ['\0\0\0\0\0\0\0\0']
pop = rootl.pop
pindex = {}
referenced = pindex.has_key
while rootl:
oid = pop()
if referenced(oid):
continue
# scan pickle for references
f = open(self._oid_dir+oid2str(oid))
r = f.read()
f.close()
pindex[oid2str(oid)] = r
p = r[8:]
referencesf(p, rootl)
# now delete any unreferenced entries
deleted = []
for oid in os.listdir(self._oid_dir):
if not referenced(oid) and (oid <= maxoid):
deleted.append(oid)
try:
for i in deleted:
os.unlink(self._oid_dir+i)
except:
raise POSException.TransactionError, 'I/O error during pack --
your storage is probably screwed up'
