fix: speed up provisioning even more by 10s with localdns enabled (#8338)

Author: awesomenix

e2e/vmss.go

@@ -749,6 +749,7 @@ func extractLogsFromVMLinux(ctx context.Context, s *Scenario, vm *ScenarioVM) er
 		"cluster-provision.log":            "sudo cat /var/log/azure/cluster-provision.log",
 		"kubelet.log":                      "sudo journalctl -u kubelet",
 		"aks-log-collector.log":            "sudo journalctl -u aks-log-collector",
+		"localdns.log":                     "sudo journalctl -u localdns",
 		"cluster-provision-cse-output.log": "sudo cat /var/log/azure/cluster-provision-cse-output.log",
 		"sysctl-out.log":                   "sudo sysctl -a",
 		"waagent.log":                      "sudo cat /var/log/waagent.log",

parts/linux/cloud-init/artifacts/cse_cmd.sh

@@ -192,4 +192,5 @@ LOCALDNS_MEMORY_LIMIT="{{GetLocalDNSMemoryLimitInMB}}"
 LOCALDNS_GENERATED_COREFILE="{{GetGeneratedLocalDNSCoreFile}}"
 PRE_PROVISION_ONLY="{{GetPreProvisionOnly}}"
 CSE_TIMEOUT="{{GetCSETimeout}}"
+SKIP_WAAGENT_HOLD="{{GetSkipWaAgentHold}}"
 /usr/bin/nohup /bin/bash -c "/bin/bash /opt/azure/containers/provision_start.sh"

parts/linux/cloud-init/artifacts/cse_main.sh

@@ -71,6 +71,11 @@ function basePrep {
         systemctl restart systemd-timesyncd
     fi
 
+    # pre-warm coredns by checking its version.
+    if [ "${SHOULD_ENABLE_LOCALDNS}" = "true" ]; then
+        nohup /bin/sh -c '/opt/azure/containers/localdns/binary/coredns --version >/dev/null 2>&1' >/dev/null 2>&1 &
+    fi
+
     # Eval proxy vars to ensure curl commands use proxy if configured.
     # e.g. PROXY_VARS=`export HTTPS_PROXY="https://proxy.example.com:8080"; export http_proxy="http://proxy.example.com:8080"; export NO_PROXY="127.0.0.1,localhost";`
     # Setting vars in etc environment (configureEtcEnvironment) won't take effect in current shell session.

pkg/agent/baker.go

@@ -1303,6 +1303,7 @@ func getContainerServiceFuncMap(config *datamodel.NodeBootstrappingConfiguration
 		},
 		"GetPreProvisionOnly": func() bool { return config.PreProvisionOnly },
 		"GetCSETimeout":       func() string { return datamodel.GetCSETimeout(config.CSETimeout) },
+		"GetSkipWaAgentHold":  func() bool { return config.EnableScriptlessNBCCSECmd },
 		"BlockIptables": func() bool {
 			return cs.Properties.OrchestratorProfile.KubernetesConfig.BlockIptables
 		},