During upgrade to 1.10 there is a brief moment when the DNS resolution will not work.
If health-check happens during that moment, it will be a failure, and thus we will see apps reported unhealthy during upgrade (whenever DNS failover happens).
We have tests to test this feature. But this has been disabled for a long time now -
[TestUpgrade.test_app_dns_survive (test_upgrade) |
TeamCity Link
As per Deepak Goel The DNS survival is not implemented yet: https://mesosphere.slack.com/archives/C0L6U3ECQ/p1503011609000296
|