Warn about potentially misconfigured connection string

[Arne Wiebalck]

In our Cinder deployment, we were facing an issue where parallel deletions of volumes (e.g. triggered by the deletion of a Magnum cluster) led to DB deadlocks, RPC timeouts and eventually inconsistent DB entries. All details can be found here [1].

In the end, it turned out that this was due to a suboptimal configuration of the DB connection string: we used "mysql://..." rather than "mysql+pymysql://..." (and were hence suffering from blocking calls causing deadlocks). In our case, this value was set once when the service was set up some years ago and never revisited.

In order to reduce the risk that others run into this issue, we were wondering if oslo would be a good place to produce a warning when detecting the "mysql://..." connection string. This would also help other potentially affected projects, not only Cinder.

[1] https://bugs.launchpad.net/cinder/+bug/1685818

[ChangBo Guo(gcb) (glongwave)]

I think we have fixed this in https://review.openstack.org/#/c/467787/

[Jay Bryant (jsbryant)]

Thanks for checking ChangBo! Looks good.