openstack team mailing list archive

["Bernhard M. Wiedemann" <bwiedemann@xxxxxxx>]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

On 04/12/2012 02:35 PM, J. Daniel Schmidt wrote:
> Dear Developers,
> 
> While testing our SUSE OpenStack packages we hit a nasty bug and
> reported it as:  https://bugs.launchpad.net/keystone/+bug/972502
> 
> We found out that the underlying cause was a lack of referential
> integrity[1] using sqlite or mysql. When we tried to reproduce this
> issue on postgresql the usage of foreign keys greatly helped to
> find the cause.
> 
> In order to prevent further inconsistencies we created a patch that
> added more foreign keys: https://review.openstack.org/6216
> 
> One reviewer commented:
>> i don't approve of adding foreign keys, and we should probably
>> remove the existing ones (in UserTenantMembership and in
>> Endpoint)
> 
> and on 
> https://review.openstack.org/#patch,sidebyside,6216,3,keystone/identity/backends/sql.py
>>
> 
we shouldn't be using foreign keys at all, they are a crutch that are not
>> available everywhere
> 
> This was a surprising answer to us as the usage of the foreign keys
> revealed the inconsistency in the first place. So removing them
> elsewhere does in no way improve the situation, it even does not
> help for mysql and sqlite, as SQLAlchemy abstracts them away. We
> also found similar bugs elsewhere:
> 
> * https://bugs.launchpad.net/keystone/+bug/959294 *
> https://bugs.launchpad.net/keystone/+bug/973243 *
> https://bugs.launchpad.net/keystone/+bug/974199
> 
> In our point of view foreign keys should be used in all possible
> places. This would not harm any database that does not support them
> but helps all of us to find data inconsistencies and related bugs,
> which leads to faster development with fewer bugs.
> 
> 
> What is your take on these things? How would you take care of data
> consistency otherwise?
> 
> 
> Thank you for your feedback, Berhard M. Wiedemann J. Daniel
> Schmidt
> 
> [1]: http://en.wikipedia.org/wiki/Referential_integrity


Just saw another bug, that would have been caught earlier with foreign
keys:
https://bugs.launchpad.net/nova/+bug/754900

So was this issue discussed on the OpenStack Summit?

Ciao
Bernhard M.
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2.0.18 (GNU/Linux)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iEYEARECAAYFAk+QTB8ACgkQSTYLOx37oWRf5gCdE9jLHdRY2vGKU6CZy3hVxtVe
sn0Anjg94EkYBeg2RnBSTTGKovnVLveI
=CS+y
-----END PGP SIGNATURE-----