readyz endpoint returns incorrect status on DB agent when using dynamic registration

[nickbrennan1]

When using dynamic registration for DB endpoints, if a new DB agent is started, after it joins the cluster the readyz agent will report status

{"status":"teleport is starting and hasn't joined the cluster yet"}

...until a DB resource is launched on that agent. Once the agent has a DB resource assigned the readyz endpoint will then return

{"status":"ok"}

The endpoint on that agent then behaves as expected and returns ok status, even if the DB resource is deleted. However, if the DB resource is deleted so the agent is serving no databases, and the agent is then restarted, readyz will then return a status of not having joined the cluster, even though a reverse tunnel to the proxy exists.

Expected behaviour would be that once the agent has joined the cluster and a reverse tunnel is in place, readyz would return ok consistently.

Reproduction Steps

As minimally and precisely as possible, describe step-by-step how to reproduce the problem.

1. Create DB agent and watch it join the cluster
2. curl http://localhost:3000/readyz.
3. Add DB resource and repeat scenario as described above

Server Details

• Teleport version (run teleport version): 8.1.1
• Server OS (e.g. from /etc/os-release): Ubuntu 20.04
• Where are you running Teleport? (e.g. AWS, GCP, Dedicated Hardware): AWS