Kubernetes client not configured in startup handler

[Richárd Lenkovits]

Keywords

kubernetes startup handler api access

Problem

I was trying to run some kubernetes client operations in the startup handler but I was getting request errors from the kube API server. Later I realized that the reason was that in the @kopf.on.startup() handler somehow kubernetes credentials are not automatically configured, as they are in event handlers.

To illustrate the point, this code failed being unable to reach the API server:

@kopf.on.startup()
def startup_operator(settings: kopf.OperatorSettings, logger, **kwargs):
    api = kubernetes.client.CoreV1Api()
    ns = api.list_namespace()
    print(ns)

But by adding the config everything runs fine:

@kopf.on.startup()
def startup_operator(settings: kopf.OperatorSettings, logger, **kwargs):
    kubernetes.config.load_kube_config()
    # or kubernetes.config.load_incluster_config() to use serviceaccount when running in a pod
    api = kubernetes.client.CoreV1Api()
    ns = api.list_namespace()
    print(ns)

Is this intentional?

[Richárd Lenkovits]

Hi, please spare some time to answer this query.

[Sergey Vasilyev]

Hello. This is not intentional, but it is so by design.

The startup handler is called very early in the lifecycle of an operator — much earlier than the K8s API clients are configured (in the on-login handlers). As such, there are no credentials yet — you have to login explicitly.

[Richárd Lenkovits]

Noted! Thank you very much for the answer!