[Trac] IntegrityError: columns cookie, ipnr, name are not unique

Hi!

We have been receiving this error when trying to log in our trac
wikis.

We have determined that this is due to how Trac manages session
cookies and a yet unknown condition that leads Trac to generate
repeated cookies in a short span of time.

This condition has probably not to do with Trac itself, but with the
underlying random number generation infrastructure, we have to
investigate this more.

Session cookies for a user are generated at every log in attempt and
are stored in a table. Cookies older than 10 days are cleaned up when
the user logs out.

If the user doesn't use the log out feature, but simply closes his
browser after a session the cookies accumulate indefinitely. If, for
some reason, the random generator produces a cookie that already
exists in the table we get the IntegrityError mentioned in the subject
of this message.

While Trac's cookie management can perhaps use some improvement, we
are more concerned about the RNG producing repeated numbers in such a
short amount of time, since this seems to point to a lack of entropy
that might have negative consequences on cipher algorithms.

Our Trac server is running on an OpenVZ virtual server. Our software
setup includes:

- CentOS 5, both in the virtual and the hardware server.
- Kernel  2.6.18-92.1.13.el5.028stab059.6
- httpd-2.2.3-11.el5_1.centos.3
- trac-0.11.1-1.el5.rf

In order to help us tracking down the responsible of this lack of
entropy we would be interested to know of other users who might be
experiencing a similar condition and what is their software setup.

Kind regards,

L

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