A controller or router that is starved shows up as slow handlers, timeouts and
back-pressure, all of which look like faults in whatever happened to be running
at the time. Nothing in the metrics said whether the host itself had capacity, so
telling a slow component from a slow machine meant going to the host.
- reports host CPU and memory usage through the existing metrics registry, on
both the controller and the router
- carries them on the metrics message so they arrive with everything else rather
than needing a separate collection path
- is off unless enabled, since the collection reads the OS on an interval
Unrelated to gossip; it was committed as part of that work and is separated here.
(cherry picked from commit bdab4b4aba)
Paul Lorenz
bc4be42832