ipython/ipython — pull request #1267 by minrk (2012-01-14 06:25:02+00:00)
Title: add NoDB for non-recording Hub

When used, this turns database-writes into no-ops, and raises KeyErrors on accesses.

Useful for minimizing Hub memory consumption under high load.

Any request for db-stored information will fail:

* `rc.hub_history()`
* `rc.resubmit()`
* `rc.db_query()`
* `rc.get_result()` for tasks submitted by other Clients.

The real database backends have good memory behavior for long-running clusters, but are poor when lots of data is flowing through the schedulers, because they are too slow to push data to the database.