[ZODB-Dev] misleading exception

[dvd]

Hi all,
I'm still working with savepoints and today I spend about tewo hours to
find an error, misleaded by a strange Exception

ZODB: 3.5.1
<code>
from ZODB import FileStorage, DB
from BTrees.OOBTree import OOBTree

import transaction

def CreateDatabase(fname, creds):
    uid, password = creds
    
    try: os.unlink(fname)
    except Exception: pass
    try: os.unlink(fname + '.index')
    except Exception: pass
    try: os.unlink(fname + '.tmp')
    except Exception: pass
    
    fstorage = FileStorage.FileStorage(fname)
    db = DB(fstorage)
    try:
        conn = db.open()
        try:
	    try:
		    root = conn.root()
		    root['users'] = OOBTree()
		    root['files'] = OOBTree()
		    root['collections'] = OOBTree()
		    root['relation'] = None
		    transaction.get().commit()

		    root['users'][uid] = password
		    transaction.get().commit()
	    except Exception, e:
	    	print "Exception occurs",e 
		raise 
        finally:
	    transaction.get().abort()
            conn.close()
    finally:
        db.close()
        fstorage.close()

print "First Step"
CreateDatabase("/tmp/ciao.fs", ('foo', 'bar'))

fstorage = FileStorage.FileStorage("/tmp/ciao.fs")
db = DB(fstorage)
conn = db.open()

root = conn.root()
sv = transaction.savepoint()
root['files'][1] = 1
sv.rollback()
#transaction.get().abort()
conn.close()
db.close()
fstorage.close()

# be sure the database is no longer here
import os
os.unlink("/tmp/ciao.fs")

print "Second Step"
CreateDatabase("/tmp/ciao.fs", ('foo', 'bar'))
</code>

If I run the code above I obtain an obscure (for me) traceback:

Traceback (most recent call last):
  File "pp.py", line 62, in ?
    CreateDatabase("/tmp/ciao.fs", ('foo', 'bar'))
  File "pp.py", line 27, in CreateDatabase
    transaction.get().commit()
  File "/usr/lib/python2.3/site-packages/transaction/_transaction.py",
line 389, in commit
    self._saveCommitishError() # This raises!
  File "/usr/lib/python2.3/site-packages/transaction/_transaction.py",
line 387, in commit
    self._commitResources()
  File "/usr/lib/python2.3/site-packages/transaction/_transaction.py",
line 430, in _commitResources
    rm.tpc_begin(self)
  File "/usr/lib/python2.3/site-packages/ZODB/Connection.py", line 468,
in tpc_begin
    self._normal_storage.tpc_begin(transaction)
  File "/usr/lib/python2.3/site-packages/ZODB/BaseStorage.py", line 214,
in tpc_begin
    self._clear_temp()
  File
"/usr/lib/python2.3/site-packages/ZODB/FileStorage/FileStorage.py", line
851, in _clear_temp
    self._tfile.seek(0)
ValueError: I/O operation on closed file

If I decomment the following line
#transaction.get().abort()

all works fine.

The strange is that the exception is raised when i try to commit the
transaction in the second call of CreateDatabase

If i omit the savepoint rollback *and* the abort line I obtain a
meaningful error:

ZODB.POSException.ConnectionStateError: Cannot close a connection joined
to a transaction

Maybe this report can help someone

bye
david

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