"Registration of the CRI-O Container Factory Failed" log entries in Kubelet

[phantomsixthplayer]

We have identified an issue within the kubelet service that results in log entries related to CRI-O connection problems if CRI-O is not used. Upon investigation, it appears that the root cause lies within the cadvisor component, as it attempts to connect to CRI-O and generates error logs in the process.

The specific log entries we are observing are as follows:

Jan 07 23:21:12 k8s-control-plane-1 kubelet[7674]: I0107 23:21:12.670850 7674 plugin.go:41] CRI-O not connected: Get "http://%2Fvar%2Frun%2Fcrio%2Fcrio.sock/info": dial unix /var/run/crio/crio.sock: connect: no such file or directory
Jan 07 23:21:12 k8s-control-plane-1 kubelet[7674]: I0107 23:21:12.685783 7674 factory.go:219] Registration of the crio container factory failed: Get "http://%2Fvar%2Frun%2Fcrio%2Fcrio.sock/info": dial unix /var/run/crio/crio.sock: connect: no such file or directory
Jan 07 23:21:18 k8s-control-plane-1 kubelet[8207]: I0107 23:21:18.396225 8207 plugin.go:41] CRI-O not connected: Get "http://%2Fvar%2Frun%2Fcrio%2Fcrio.sock/info": dial unix /var/run/crio/crio.sock: connect: no such file or directory
Jan 07 23:21:18 k8s-control-plane-1 kubelet[8207]: I0107 23:21:18.426071 8207 factory.go:219] Registration of the crio container factory failed: Get "http://%2Fvar%2Frun%2Fcrio%2Fcrio.sock/info": dial unix /var/run/crio/crio.sock: connect: no such file or directory

Upon further examination, it seems that the CRI-O connection attempts are initiated by cadvisor during its initialization process. The relevant code snippets in cadvisor can be found in the following locations:

1. CRI-O not connected log message origin:
   

   cadvisor/container/crio/plugin.go

   Line 41 in 04006e5

   klog.V(5).Infof("CRI-O not connected: %v", err)

2. CRI-O registration failure log message origin:
   

   cadvisor/container/crio/install/install.go

   Lines 25 to 30 in 04006e5

   	func init() {
   	err := container.RegisterPlugin("crio", crio.NewPlugin())
   	if err != nil {
   	klog.Fatalf("Failed to register crio plugin: %v", err)
   	}
   	}

3. Issue raised with Kubernetes:
   confusing CRI-O error from cadvisor for nodes that use containerd kubernetes/kubernetes#122632