Soft deleting instances and the reclaim_instance_interval in Nova

I got asked the other day how the reclaim_instance_interval in Nova works, so I thought I’d write it up here in case its useful to other people.

First off, there is a periodic task run the nova-compute process (or the computer manager as a developer would know it), which runs every reclaim_instance_interval seconds. It looks for instances in the SOFT_DELETED state which don’t have any tasks running at the moment for the hypervisor node that nova-compute is running on.

For each instance it finds, it checks if the instance has been soft deleted for at least reclaim_instance_interval seconds. This has the side effect from my reading of the code that an instance needs to be deleted for at least reclaim_instance_Interval seconds before it will be removed from disk, but that the instance might be up to approximately twice that age (if it was deleted just as the periodic task ran, it would skip the next run and therefore not be deleted for two intervals).

Once these conditions are met, the instance is deleted from disk.

Historical revisionism

I have spotted a worrying trend with one of the email lists I archive. So far I have fielded about ten requests to remove emails from the archive, with four of those being in the last couple of weeks. I wont name the offenders, but handling these requests takes a fair bit of time on my part. So, I ask for opinions. Should I be deleting emails from a public archive, given the mailing list is open to subscription from anyone? Does it matter that this is a third party archive, and I am not the list administrator? Should people think before they post?

Given the long memory of search engines, and the increasing probability of an employer Googling for you before hiring, I wonder if this sort of request is going to become so common that it endangers the public archival of things like mailing lists?

A penny for your thoughts…