0 response code on WATCH against the kubernetes api server

[Erez Rabih]

We recently upgraded our kubernetes control plane from version 1.13 to 1.16

After doing that, we started seeing 0 (zero) response codes on the prometheus reporting dashboard for WATCH operations against the apiserver.

The metric we're using is

sum(rate(apiserver_request_count{code!~"^2.*$"}[1m])) by (code, resource, subresource, verb)

I tried searching for any clue of what might be the cause and the only one I found is https://github.com/kubernetes/kubernetes/issues/16686

Is it something we should be worried about or is it just a nuance of the new apiserver?

Thanks for any help!