Improving health checks validation (MESOS-6916)

[Gastón Kleiman <ga...@mesosphere.io>]

Hi all,

I'd like to improve the validation of the `HealthCheck` message (MESOS-6916
<https://issues.apache.org/jira/browse/MESOS-6916>).

I want to make sure that my proposed changes won't conflict with how people
are using Mesos today, so please let me know if a validation enforcing the
following extra constraints would fail with your current health checks:

   1. 'delay_seconds' must be non-negative.
   2. 'interval_seconds' must be non-negative.
   3. 'timeout_seconds' must be non-negative.
   4. 'grace_period_seconds' must be non-negative.
   5. If `type` is `HTTP[S]`, then 'HealthCheck.HTTPCheckInfo.port' must be
   greater than zero.
   6. If `type` is `TCP`, then 'HealthCheck.TCPCheckInfo.port' must be
   greater than zero.
   7. 'consecutive_failures' must be non-negative.
   8. Mesos treats `consecutive_failures = 0` in the same way as
   `consecutive_failures = 1` (MESOS-6833
   <https://issues.apache.org/jira/browse/MESOS-6833>). I propose allowing
   `consecutive_failures = 0`, but changing the semantics, so that executors
   don't kill the task if it fails the health checks.

Looking forward to your replies,

-Gastón