This should also have better latency due to being a single query.
Furthermore, it's no longer a linear scan, since host is indexed.
Would be cool to simplify it further to a single query for blocks also...
Why exactly are blocks not in the db?
It works by having a day-long cache of
"when did we last successfully communicate with this instance?"
Anything over a specified threshold (1 month) will act as though the instance
is suspended - all outgoing jobs are dropped on processing.
The day-long cache is in place because the ordering is necessarily a
linear scan.
Once an instance comes back online, we will detect that is the case as soon as
we receive an activity from them (which will update the "last communicated at")
field.
Potential future TODOs:
* Improve the caching system, it's actually pretty inefficient as it is.
CacheBox with a call override?
* Think of ways to make it not-a-linear-scan, since the instances table can get
pretty big. It's around 4500 on toast cafe.
ChangeLog: Added
