Pulp

With the PR for 3456 being merged I don't think sqlite is emitting OperationDatabaseLocked anymore.

https://github.com/pulp/pulp/pull/3405

I still think we should make the change because developers doing hand testing may need to run very heavy loads in the process of debugging certain issues.

I think it's still the other way around because it's much easier to switch from postgres to sqlite than to switch from sqlite to postgres.

And if we reach a point where our ** smoke tests are failing on sqlite due to sqlite limitations rather than logic flaws, we should seriously reconsider supporting sqlite to begin with.

Each time we've hit a problem with sqlite it's been an opportunity for us to improve Pulp's ability to run in more places. With the recent sqlite timing changes, I don't know of any current workflows that raise OperationalError. If Pulp+sqlite is broken somehow and it is unfixable that would be very useful info.

The problem seems to be that even though SQLite supports a better concurrency model[0] already, Django does not take advantage of it[1].

The Django issue has a suggestion[2] to use the 'connection_created' signal to make Pulp use sqlite with the WAL mode. We should probably do exactly that.

[0] http://www2.sqlite.org/wal.html
[1] https://code.djangoproject.com/ticket/24018
[2] https://stackoverflow.com/questions/4534992/place-to-set-sqlite-pragma-option-in-django-project/6843199#6843199