🐛fix ClusterCache doesn't pick latest kubeconfig secret proactively

[mogliang]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #12399

/area clustercache

[linux-foundation-easycla]

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• ✅ login: mogliang / name: Mog Liang (8ce65c7, 8e7dc16, 754d34a)

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[mogliang]

added unit test

[sivchari]

/ok-to-test

[sbueringer]

You are hitting tooManyConsecutiveFailures in your scenario, right?

Would it also be enough for your use case to make HealthProbe.Timeout/Interval/FailureThreshold configurable?

[mogliang]

not really.
We have proxy between mgmt cluster and target clusters.
we see after kubeconfig updated (proxy address changed), the existing connection (clustercache probe) still works, so it doesn't refetch kubeconfig and still cache the old one, but new connections fails (etcd client)

[sbueringer]

So if the health check would open a new connection it would detect it, right?

[mogliang]

that's correct~ another idea is to disconnect for a given time (e.g. 5m) period to force refresh connection. will this be better?

[sbueringer]

I would just try to extend the health check that it does two requests. One over the existing connection one with a new connection

[sbueringer]

client-go will reuse the underlying transport (except create spdy transport).

Do you know where that happens? Somewhere in rest.HTTPClientFor or rest.TransportFor or transport.New?

[mogliang]

in transport.New

if restconfig has .Tranport, it will just use it, if not, it will get from cache.

// New returns an http.RoundTripper that will provide the authentication
// or transport level security defined by the provided Config.
func New(config *Config) (http.RoundTripper, error) {
	// Set transport level security
	if config.Transport != nil && (config.HasCA() || config.HasCertAuth() || config.HasCertCallback() || config.TLS.Insecure) {
		return nil, fmt.Errorf("using a custom transport with TLS certificate options or the insecure flag is not allowed")
	}

	if !isValidHolders(config) {
		return nil, fmt.Errorf("misconfigured holder for dialer or cert callback")
	}

	var (
		rt  http.RoundTripper
		err error
	)

	if config.Transport != nil {
		rt = config.Transport
	} else {
		rt, err = tlsCache.get(config)
		if err != nil {
			return nil, err
		}
	}

[sbueringer]

Wondering if there is a good way to pass in a transport, without duplicating too much code

[mogliang]

let it check it

[mogliang]

@sbueringer
https://github.com/kubernetes-sigs/cluster-api/compare/release-1.9...mogliang:cluster-api:dev/qliang/v1.9.5-fixetcd2?expand=1

copied the implemenation from tlscache.get.

need mention that, establish tcp connection takes ~1sec in our case, and normal ping may take ~100sec. so, this do adds some reconcile time.

[mogliang]

/hold