[horde] Session overflow

Michael M Slusarz slusarz at horde.org
Tue Feb 19 00:25:53 UTC 2013

Quoting Claude Tompers <claude.tompers at restena.lu>:

> On 02/17/2013 07:22 AM, Michael M Slusarz wrote:
>> Quoting Claude Tompers <claude.tompers at restena.lu>:
>>> Hello,
>>> We just found some powerusers in our horde system with Session data in
>>> MySQL bigger than 64k (max size of type blob) causing horde to crash and
>>> log them out.
>>> MySQL cuts the serialized session object after 64k so when Horde reads
>>> it again, it is not valid anymore.
>>> We changed the SessionHandler.Session_Data column in the horde database
>>> to mediumblob (16M) and the problem disappeared immediately.
>>> Is this a known issue ?
>> Yes - in fact, it is expressly mentioned in the main horde
>> configuration file (horde/config/conf.xml).
> My conf.xml only mentions the horde_prefs table, not the SessionHandler.
> Are there other tables that can have the same issue ?

Sure.  Any database table you are using that contains blob-ish data.

>>> I suppose we are not the only ones with such
>>> power users.
>>> Shouldn't Horde log warnings of such overflows from MySQL ?
>> IIRC, there is no warning (at least there used to not be).  MySQL
>> silently discards all data over 64 KB.
> I talked to my colleague who said that it is possible that MySQL does
> not only send a warning, but a fatal error in these conditions.
> He pointed me to the following document :
> http://dev.mysql.com/doc/refman/5.0/en/server-sql-mode.html#sqlmode_strict_all_tables
> Would this be possible to do in Horde or are there other restrictions ?

Patches are welcome.  I personally have no idea how mysql works since  
I don't use it.


Michael Slusarz [slusarz at horde.org]

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