Re: Appropriate use of HTTP status codes for application health checks

[Willy Tarreau <[e-mail]>]

Hi Amos,

On Thu, Feb 23, 2017 at 10:53:07PM +1300, Amos Jeffries wrote:
> IMHO a better efficient way for a polling system is to use 204 as "All
> okay", and 200 as "some problem(s)". No bandwidth wasted with payload on
> the common Up status, and ability to deliver details about the outage on
> the Down status.

In fact it's common to see health check applications return 5xx for a
very simple reason, the front equipment performing the check (often a
load balancer) has to deal with these situations anyway, and most use
cases just want to return "completely up" or "completely dead". But I
agree that when you want to support the gray area in between, it's much
better to support intermediary codes. FWIW haproxy also supports a
special case of 404 to mean "closing soon, no more requests please" so
that admins can simply touch/rm a file in a docroot. That's just to say
that there are many valid use cases and tha common sense adapted to what
components *reliably* support is often the best here.

Cheers,
Willy