"citadel_server_root_cert_expiry_timestamp",
		"The unix timestamp, in seconds, when Citadel root cert will expire. "+
			"A negative time indicates the cert is expired.",
	)
	rootCertExpirySeconds = monitoring.NewDerivedGauge(
		"citadel_server_root_cert_expiry_seconds",
		"The time remaining, in seconds, before the root certificate will expire. "+
			"A negative value indicates the cert is expired.",
	)

)

type monitor struct {
	monitoringServer *http.Server
}

const (
	metricsPath = "/metrics"
	versionPath = "/version"
)

var (
	serverStart = time.Now()

	_ = monitoring.NewDerivedGauge(
		"istiod_uptime_seconds",
		"Current istiod server uptime in seconds",
	).ValueFrom(func() float64 {
		return time.Since(serverStart).Seconds()
	})

	versionTag   = monitoring.CreateLabel("version")