pluginAuthnServiceFailedRequestsMinute = "plugin_authn_service_failed_requests_minute"
	pluginAuthnServiceLastFailSeconds      = "plugin_authn_service_last_fail_seconds"
	pluginAuthnServiceLastSuccSeconds      = "plugin_authn_service_last_succ_seconds"
	pluginAuthnServiceSuccAvgRttMsMinute   = "plugin_authn_service_succ_avg_rtt_ms_minute"
	pluginAuthnServiceSuccMaxRttMsMinute   = "plugin_authn_service_succ_max_rtt_ms_minute"

	if !globalIAMSys.Initialized() {
		writeSTSErrorResponse(ctx, w, ErrSTSIAMNotInitialized, errIAMNotInitialized)
		return
	}

	authn := newGlobalAuthNPluginFn()
	if authn == nil {
		writeSTSErrorResponse(ctx, w, ErrSTSNotInitialized, errors.New("STS API 'AssumeRoleWithCustomToken' is disabled"))
		return
	}

	action := r.Form.Get(stsAction)