Mark a service as unhealthy for a certain time period.

[WouterBaeyens]

Feature Description

I want to be able to mark a service as unhealthy for a certain time period.

This could be accomplished in a number of ways:

• a TTL mechanism that flips the client out of maintenance mode
• a TTL check that defaults to healthy.

Use Case(s)

If I can predict my service will go down, I want to avoid directing users to this failing service.

Currently I have no good way to avoid a percentage of the user-base going to this unhealthy service until another health-check picks up on it.

• current health checks have a small delay
• maintenance mode has to be manually disabled.
  If the request to disable maintenance mode fails, the service stays unreachable.
• a TTL check introduces the burden of converting the service to constantly send it's current status.

Introducing a TTL for maintenance was part of a suggestion in #345 and I don't think a workaround for my use-case currently exists.
(see my question on Stack Overflow)

[pearkes]

If I understand correctly, my guess is we wouldn't want to add some sort of "unhealthy time period" feature. We'd recommend explicitly transitioning a service to healthily and not during maintenance.

So:

1. Enable maintenance mode for a service
2. Perform whatever operation
3. Unset maintenance mode

You could do this from a 3rd system that has a timer to automate in a way that you specify. However, typically the use-case for people is that maintenance could take an unknown amount of time, and choosing and end time before maintenance begins could pose other risks.

I hope that makes sense. Thank you for opening an issue!

[WouterBaeyens]

My original idea was to send a ttl that defaults to healthy from an onShutdown event of my server.
This would remove the delay for Consul to notice the service being unhealthy if I were to only use pings.

I agree, that in the use-case of planned maintenance a timer might pose certain risks.
If the use-cases for this feature are indeed to small in comparison to the needed effort, it saddens me a little, but I understand.

Thank you for your reply!