10/23: Healthchecking

[shimmerjs]

health checking

command check: supervisor executes binary against environment, returns exit code back to supervisor.

this talk was mostly way too low level for my interest, but one interesting tidbit that enforces things i've already been thinking:

if svc a depends on svc b, and svc b is marked unhealthy, do not automatically mark svc a as unhealthy:

1. your policy will be the same, and will not be effective. the policy for handling unhealthy svc b will automatically make svc a fully functional again.
2. use additional checks, such as degraded state, and readiness checks.