This is a test script, to help me to understand why I have unexpected
result in application.
But I got a more unexpected result, and probably wrong error message
about the read-only cursor.
The full script is at the end.

I got this only one ! I restart the script after the crash, but
this has freezed my xen virtual machine after some minutes. I had to
"destroy" it and restart it. 
After restart was not working anymore, blocked, not responding except to
CTRL-C
I had to drop the old DB, and then i worked again 

I run python 2.5.2 inside a kolab 2.2.0 (aka openpkg) environement 
on a xen centos 5.x running kernel 2.6.18-8.el5xen and glibc-2.5-12

The host is a P4 running centos 5.X and kernel 2.6.18-53.1.4.el5xen


Here are the errors, I waited for long time after the  firts backtrace,
to press CTRL-C and got immediately the second backtrace.

Regards

db cleanup, 326 records deleted, 9990 remains
Exception in thread Thread-1:
Traceback (most recent call last):
  File "/kolab/lib/python/threading.py", line 486, in
__bootstrap_inner
    self.run()
  File "/kolab/lib/python/threading.py", line 446, in run
    self.__target(*self.__args, **self.__kwargs)
  File "./test/test_bdb.py", line 85, in <lambda>
    update_thread=threading.Thread(target=lambda : cleanup(db))
  File "./test/test_bdb.py", line 72, in cleanup
    cursor.delete()
DBPermissionsError: (1, 'Operation not permitted -- Write attempted on
read-
only
cursor')

Traceback (most recent call last):
  File "./test/test_bdb.py", line 130, in <module>
    server()
  File "./test/test_bdb.py", line 92, in server
    db[str(last)]=str(last)
KeyboardInterrupt
*** glibc detected *** /kolab/bin/python: double free or corruption
(fasttop):
0
x09d521a8 ***
======= Backtrace: =========
/lib/i686/nosegneg/libc.so.6[0x4444ccfd]
/lib/i686/nosegneg/libc.so.6(cfree+0x90)[0x444503b0]
/kolab/bin/python(__db_c_destroy+0x60)[0x81fa6f0]
/kolab/bin/python(__db_refresh+0x165)[0x81f3515]
/kolab/bin/python(__db_close+0x64)[0x81f3cb4]
/kolab/bin/python(__db_close_pp+0xa1)[0x8204b61]
/kolab/bin/python[0x812123f]
/kolab/bin/python[0x8159534]
/kolab/bin/python[0x815fb0a]
/kolab/bin/python[0x811abbc]
/kolab/bin/python[0x811abc9]
/kolab/bin/python[0x80b0229]
/kolab/bin/python(PyDict_SetItem+0x6e)[0x80b1c0e]
/kolab/bin/python(PyDict_SetItemString+0x42)[0x80b1ce2]
/kolab/bin/python(PyImport_Cleanup+0xd4)[0x8108294]
/kolab/bin/python(Py_Finalize+0xbf)[0x8113f1f]
/kolab/bin/python(Py_Main+0x468)[0x80845c8]
/kolab/bin/python(main+0x22)[0x8084052]
/lib/i686/nosegneg/libc.so.6(__libc_start_main+0xdc)[0x443fbdec]
/kolab/bin/python[0x8083fa1]
======= Memory map: ========
00110000-001d7000 rwxp 00110000 00:00 0
001d7000-001da000 r-xp 00000000 ca:03 973941     /kolab/lib/python/lib-
dynload/
t
ime.so
001da000-001dc000 rwxp 00002000 ca:03 973941     /kolab/lib/python/lib-
dynload/
t
ime.so
001dc000-001e0000 r-xp 00000000 ca:03 973938     /kolab/lib/python/lib-
dynload/
s
trop.so
001e0000-001e2000 rwxp 00003000 ca:03 973938     /kolab/lib/python/lib-
dynload/
s
trop.so
001e2000-001e3000 r-xp 00000000 ca:03 973911     /kolab/lib/python/lib-
dynload/
_
weakref.so
001e3000-001e4000 rwxp 00000000 ca:03 973911     /kolab/lib/python/lib-
dynload/
_
weakref.so
001e4000-001ea000 rwxs 00000000 ca:03 1747650    /tmp/db/__db.001
001ea000-001fc000 rwxs 00000000 ca:03 1747651    /tmp/db/__db.002
001fc000-0023e000 rwxs 00000000 ca:03 1747652    /tmp/db/__db.003
00388000-003e0000 rwxs 00000000 ca:03 1747653    /tmp/db/__db.004
00450000-00452000 r-xp 00000000 ca:03 1132355    /lib/libutil-2.5.so
00452000-00453000 r-xp 00001000 ca:03 1132355    /lib/libutil-2.5.so
00453000-00454000 rwxp 00002000 ca:03 1132355    /lib/libutil-2.5.so
00459000-0047e000 r-xp 00000000 ca:03 1132349    /lib/i686/nosegneg/
libm-2.5.so
0047e000-0047f000 r-xp 00024000 ca:03 1132349    /lib/i686/nosegneg/
libm-2.5.so
0047f000-00480000 rwxp 00025000 ca:03 1132349    /lib/i686/nosegneg/
libm-2.5.so
0063e000-0063f000 r-xp 0063e000 00:00 0          [vdso]
0097a000-0098d000 r-xp 00000000 ca:03 1134447    /lib/i686/nosegneg/
libpthread-2                                                           
                                                                      .
5.so
0098d000-0098e000 r-xp 00012000 ca:03 1134447    /lib/i686/nosegneg/
libpthread-2                                                           
                                                                      .
5.so
0098e000-0098f000 rwxp 00013000 ca:03 1134447    /lib/i686/nosegneg/
libpthread-2                                                           
                                                                      .
5.so
0098f000-00991000 rwxp 0098f000 00:00 0
009a8000-009e9000 rwxp 009a8000 00:00 0
00b80000-00d80000 r-xp 00000000 ca:03 845325     /usr/lib/locale/
locale-archive
00ec9000-00ecc000 r-xp 00000000 ca:03 973916     /kolab/lib/python/lib-
dynload/
c
StringIO.so
00ecc000-00ecd000 rwxp 00003000 ca:03 973916     /kolab/lib/python/lib-
dynload/
c
StringIO.so
00fd2000-00fd6000 r-xp 00000000 ca:03 973918     /kolab/lib/python/lib-
dynload/
c
ollections.so
00fd6000-00fd7000 rwxp 00004000 ca:03 973918     /kolab/lib/python/lib-
dynload/
c
ollections.so
00fd7000-00fd8000 --xp 00fd7000 00:00 0
00fd8000-019d8000 rwxp 00fd8000 00:00 0
08048000-08433000 r-xp 00000000 ca:03 430731     /kolab/bin/python
08433000-0846e000 rwxp 003eb000 ca:03 430731     /kolab/bin/python
0846e000-08478000 rwxp 0846e000 00:00 0
09ce5000-09da5000 rwxp 09ce5000 00:00 0
443c4000-443dd000 r-xp 00000000 ca:03 1132323    /lib/ld-2.5.so
443dd000-443de000 r-xp 00018000 ca:03 1132323    /lib/ld-2.5.so
443de000-443df000 rwxp 00019000 ca:03 1132323    /lib/ld-2.5.so
443e6000-44521000 r-xp 00000000 ca:03 1134399    /lib/i686/nosegneg/
libc-2.5.so
44521000-44523000 r-xp 0013a000 ca:03 1134399    /lib/i686/nosegneg/
libc-2.5.so
44523000-44524000 rwxp 0013c000 ca:03 1134399    /lib/i686/nosegneg/
libc-2.5.so
44524000-44527000 rwxp 44524000 00:00 0
44529000-4452b000 r-xp 00000000 ca:03 1134402    /lib/libdl-2.5.so
4452b000-4452c000 r-xp 00001000 ca:03 1134402    /lib/libdl-2.5.so
4452c000-4452d000 rwxp 00002000 ca:03 1134402    /lib/libdl-2.5.so
44622000-4462d000 r-xp 00000000 ca:03 1134413    /lib/
libgcc_s-4.1.1-20070105.so                                             
                                                                       
            .
1Aborted

#!/kolab/bin/python

import os, sys, logging, time, threading
import marshal
import bsddb.db

# this is a test to see how bsddb is reliable
# The server count in the db, and the client search for missing value
# run on server in a terminal, and a client in another

#
======================================================================
# db functions
#
======================================================================

db_dir='/tmp/db'
db_filename=os.path.join(db_dir, 'test.bdb')

try:
    os.mkdir(db_dir)
except OSError:
    pass

freq=100 # new sample per/sec
timeout=3 # in sec, how long I wait for them
retention=100 # in sec, how long they stay in the db

def init_db(read_only=True):
    # open the environement
    dbenv=db=None
    try:
        db_env=bsddb.db.DBEnv(0)

        flags=bsddb.db.DB_CREATE | bsddb.db.DB_INIT_CDB |
bsddb.db.DB_INIT_MPOOL
        db_env.open(db_dir, flags)
        db=bsddb.db.DB(db_env)
        flags = bsddb.db.DB_DIRTY_READ | ( bsddb.db.DB_RDONLY if
read_only else bsddb.db.DB_CREATE )

        db.open(db_filename, dbtype=bsddb.db.DB_HASH,flags=flags)
    except Exception:
        print 'error opening db'
        raise
    else:
        print 'db opened'

    return dbenv, db

#
----------------------------------------------------------------------
def close_db(dbenv, db):
    try:
        if db:
            db.close()
        if dbenv:
            db_env.close()
    except Exception:
        log.rcpt.exception('closing db')
    else:
        log.rcpt.info('db closed')

#
----------------------------------------------------------------------
def now():
    return int(time.time()*freq)

def cleanup(db):

    while True:
        cursor=db.cursor(None, bsddb.db.DB_WRITECURSOR)
        count=remain=0
        c=cursor.first()
        limit=now()-retention*freq
        while c:
            k, v=c
            t=int(k)
            if t<=limit:
                cursor.delete()
                count+=1
            else:
                remain+=1
            c=cursor.next()
        cursor.close()
        print 'db cleanup, %d records deleted, %d remains' % (count,
remain)
        time.sleep(timeout)

def server():
    dbenv, db=init_db(read_only=False)

    update_thread=threading.Thread(target=lambda : cleanup(db))
    update_thread.setDaemon(True)
    update_thread.start()
    last=now()
    while True:

        while last<now():
            db[str(last)]=str(last)
            last+=1

        time.sleep(1/freq)

    close_db(dbenv, db)

def client():

    dbenv, db=init_db(read_only=True)

    max_delay=0
    last=now()

    while True:
        try:
            value=db[str(last)]
        except KeyError:
            if last<now()-timeout*freq:
                print 'not found', last, float(now()-last)/freq
                last+=1
            else:
              time.sleep(1/freq)
        else:
            delay=now()-last
            if delay>max_delay:
                max_delay=delay
                print 'delay', max_delay

            last+=1

    close_db(dbenv, db)

if sys.argv[1]=='c':
    client()
elif sys.argv[1]=='s':
    server()