[openstack-dev] [oslo][db] Mysql traditional session mode

Ben Nemec openstack at nemebean.com
Thu Jan 23 18:22:39 UTC 2014


On 2014-01-23 12:03, Florian Haas wrote: 

> Ben, 
> thanks for taking this to the list. Apologies for my brevity and for HTML, I'm on a moving train and Android Gmail is kinda stupid. :)

I have some experience with the quirks of phone GMail myself. :-) 

> On Jan 23, 2014 6:46 PM, "Ben Nemec" <openstack at nemebean.com> wrote:
>> A while back a change (https://review.openstack.org/#/c/47820/ [1]) was made to allow enabling mysql traditional mode, which tightens up mysql's input checking to disallow things like silent truncation of strings that exceed the column's allowed length and invalid dates (as I understand it).
>> IMHO, some compelling arguments were made that we should always be using traditional mode and as such we started logging a warning if it was not enabled. It has recently come to my attention (https://review.openstack.org/#/c/68474/ [2]) that not everyone agrees, so I wanted to bring it to the list to get as wide an audience for the discussion as possible and hopefully come to a consensus so we don't end up having this discussion every few months. 
> For the record, I obviously am all in favor of avoiding data corruption, although it seems not everyone agrees that TRADITIONAL is necessarily the preferable mode. But that aside, if Oslo decides that any particular mode is required, it should just go ahead and set it, rather than log a warning that the user can't possibly fix.

Honestly, defaulting it to enabled was my preference in the first place.
I got significant pushback though because it might break consuming
applications that do the bad things traditional mode prevents. My theory
was that we could default it to off, log the warning, get all the
projects to enable it as they can, and then flip the default to enabled.
Obviously that hasn't all happened though. :-) 

>> I remain of the opinion that traditional mode is a good thing and we _should_ be enabling it. I would call silent truncation and bogus date values bugs that should be fixed, but maybe there are other implications of this mode that I'm not aware of.
>> It was also pointed out that the warning is logged even if the user forces traditional mode through my.cnf. While this certainly solves the underlying problem, it doesn't change the fact that the application was trying to do something bad. We tried to make it clear in the log message that this is a developer problem and the user needs to pester the developer to enable the mode, but maybe there's more discussion that needs to go on there as well. 
> Hence my proposal to make this a config option. To make the patch as un-invasive as possible, the default for that option is currently empty, but if it seems prudent to set TRADITIONAL or STRICT_ALL_TABLES instead, I'll be happy to fix the patch up accordingly.

Also check out Jay's reply. It sounds like there are some improvements
we can make as far as not logging the message when the user enables
traditional mode globally. 

I'm still not clear on whether there is a need for the STRICT_* modes,
and if there is we should probably also allow STRICT_TRANS_TABLES since
that appears to be part of "strict mode" in MySQL. In fact, if we're
going to allow arbitrary modes, we may need a more flexible config
option - it looks like there are a bunch of possible sql_modes available
for people who don't want the blanket "disallow all the things" mode. 

> Cheers,
> Florian


[1] https://review.openstack.org/#/c/47820/
[2] https://review.openstack.org/#/c/68474/
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstack.org/pipermail/openstack-dev/attachments/20140123/82fa0c68/attachment.html>

More information about the OpenStack-dev mailing list