metabase has become a central concept and it's more suitable for it to
be directly nested under satellite rather than being part of metainfo.
metainfo is going to be the "endpoint" logic for handling requests.
Change-Id: I53770d6761ac1e9a1283b5aa68f471b21e784198
* The audit worker wants to get items from the queue and process them.
* The audit chore wants to create new queues and swap them in when the
old queue has been processed.
This change adds a "Queues" struct which handles the concurrency
issues around the worker fetching a queue and the chore swapping a new
queue in. It simplifies the logic of the "Queue" struct to its bare
bones, so that it behaves like a normal queue with no need to understand
the details of swapping and worker/chore interactions.
Change-Id: Ic3689ede97a528e7590e98338cedddfa51794e1b
* Do not swap the active audit queue with the pending audit queue until
the active audit queue is empty.
* Do not begin creating a new pending audit queue until the existing
pending audit queue has been swapped to the active queue.
Change-Id: I81db5bfa01458edb8cdbe71f5baeebdcb1b94317
