services/horizon: Throttle the reaper

[paulbellamy]

What problem does your feature solve?

When people first turn on the reaper, it monopolizes their CPU.

What would you like to see?

Add some sort of limit to how fast the reaper runs so that it runs slower, but leaves cpu/ram available for other processes.

e.g. Throttle the reap at 2x what’s needed to keep up with new stuff. Might be tricky depending on how it batches.

It does a delete all. Maybe we could add a limit.

What alternatives are there?

• Leave it and warn people