Cost efficient AMIs (review 2/14/21)

[cellistigs]

For cost efficiency, we should reduce our usage of EBS resources. We can do this as follows:

• delete all volumes not actively in use by an instance. Volumes can be recreated at will from snapshots.
• Set up a cron job to periodically delete unused volumes and snapshots. See the snapshot_utils code you have to set up a lambda function for this.
• In two weeks, delete all AMIs that are not currently referenced in a CFN stack. Send out an email to notify on this.
• Delete all unattended instances older than 6 weeks.