Support scraping metrics from target running with TLS

[pierDipi]

vLLM server can run with TLS and metrics scraping doesn't work currently in that case.

Support setting --model-server-metrics-scheme=http|https and --model-server-metrics-https-insecure-skip-verify=false|true.

The change is backward compatible.

Fixes #1189

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[k8s-ci-robot]

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[k8s-ci-robot]

Hi @pierDipi. Thanks for your PR.

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[pierDipi]

/cc @nirrozenbaum @ahg-g @kfswain

[nirrozenbaum]

/ok-to-test

[kfswain]

Looks great! Do you mind adding these flags (with the same defaults) to the helm chart? Example:

gateway-api-inference-extension/config/charts/inferencepool/templates/epp-deployment.yaml

Line 41 in 6cf8f31

- "--enable-pprof={{ .Values.inferenceExtension.enablePprof }}"

Thanks!

[pierDipi]

Thanks for the feedback Kellen, done!

[kfswain]

Looks great! Just adding a request to update helm also. Thanks!

[elevran]

Code wise - LGTM.
Not clear how the CA for the metrics endpoint certificate is added to the HTTPS client configuration in GIE.

[elevran]

how is the CA added to the TLS context? Is it intended to be added to the default certificate roots in the image?
Without adding the CA to the allowed list - won't you be forced to always use insecure-skip-verify set to true?

[ahg-g]

I agree, we should actually remove the flag for now and set this to true

[kfswain]

@elevran agreed that this is suboptimal. Unfortunately this seems to be blocking downstream & is being pushed to be included in a v0.5.1 patch. WE will move forward with this, but would like @pierDipi to create an issue to track CA validation to help prevent MITM vulnerabilites.

[pierDipi]

In Go, we can inject the default loaded CA certs file and dirs paths via env variables https://go.dev/src/crypto/x509/root_unix.go or use well-known files/directories https://go.dev/src/crypto/x509/root_linux.go:

	// certFileEnv is the environment variable which identifies where to locate
	// the SSL certificate file. If set this overrides the system default.
	certFileEnv = "SSL_CERT_FILE"

	// certDirEnv is the environment variable which identifies which directory
	// to check for SSL certificate files. If set this overrides the system default.
	// It is a colon separated list of directories.
	// See https://www.openssl.org/docs/man1.0.2/man1/c_rehash.html.
	certDirEnv = "SSL_CERT_DIR"

// Possible certificate files; stop after finding one.
var certFiles = []string{
	"/etc/ssl/certs/ca-certificates.crt",                // Debian/Ubuntu/Gentoo etc.
	"/etc/pki/tls/certs/ca-bundle.crt",                  // Fedora/RHEL 6
	"/etc/ssl/ca-bundle.pem",                            // OpenSUSE
	"/etc/pki/tls/cacert.pem",                           // OpenELEC
	"/etc/pki/ca-trust/extracted/pem/tls-ca-bundle.pem", // CentOS/RHEL 7
	"/etc/ssl/cert.pem",                                 // Alpine Linux
}

// Possible directories with certificate files; all will be read.
var certDirectories = []string{
	"/etc/ssl/certs",     // SLES10/SLES11, https://golang.org/issue/12139
	"/etc/pki/tls/certs", // Fedora/RHEL
}

func init() {
	if goos.IsAndroid == 1 {
		certDirectories = append(certDirectories,
			"/system/etc/security/cacerts",    // Android system roots
			"/data/misc/keychain/certs-added", // User trusted CA folder
		)
	}
}

do we still want to add the explicit CA path flags or we can leverage built-in/standard methods to inject custom CA bundles?

[elevran]

@pierDipi as far as I can tell, this configures Go for directory locations where CA files are located.
I think the question is which component is responsible for adding the relevant CA(s) to the EPP Pods. Without orchestrating that, we would need to skip verification on the client (EPP) side since there's no assurance the CA signing the vLLM certs is known to the EPP.
It's a process/deployment concern, not a technical limitation per-se.
Agree it's better handled in a separate issue/PR and we use insecure-skip-verify=true for now to get the encryption enabled.

[kfswain]

/lgtm
/approve

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: kfswain, pierDipi

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