runtime: display accurate error msg to avoid misleading users.

src/runtime/pkg/containerd-shim-v2/shim_management.go

@@ -338,12 +338,16 @@ func ServerSocketAddress(id string) string {
 // shim management endpoint
 // NOTE: this code allows various go clients, e.g. kata-runtime or kata-monitor commands, to
 // connect to the rust shim management implementation.
-func ClientSocketAddress(id string) string {
+func ClientSocketAddress(id string) (string, error) {
 	// get the go runtime uds path
 	socketPath := SocketPathGo(id)
 	// if the path not exist, use the rust runtime uds path instead
 	if _, err := os.Stat(socketPath); err != nil {
 		socketPath = SocketPathRust(id)
+		if _, err := os.Stat(socketPath); err != nil {
+			return "", fmt.Errorf("It fails to stat both %s and %s with error %v.", SocketPathGo(id), SocketPathRust(id), err)
+		}
 	}
-	return fmt.Sprintf("unix://%s", socketPath)
+
+	return fmt.Sprintf("unix://%s", socketPath), nil
 }

src/runtime/pkg/kata-monitor/pprof.go

@@ -32,7 +32,7 @@ func (km *KataMonitor) composeSocketAddress(r *http.Request) (string, error) {
 		return "", err
 	}
 
-	return shim.ClientSocketAddress(sandbox), nil
+	return shim.ClientSocketAddress(sandbox)
 }
 
 func (km *KataMonitor) proxyRequest(w http.ResponseWriter, r *http.Request,

src/runtime/pkg/utils/shimclient/shim_management_client.go

@@ -19,7 +19,12 @@ import (
 
 // BuildShimClient builds and returns an http client for communicating with the provided sandbox
 func BuildShimClient(sandboxID string, timeout time.Duration) (*http.Client, error) {
-	return buildUnixSocketClient(shim.ClientSocketAddress(sandboxID), timeout)
+	socketAddress, err := shim.ClientSocketAddress(sandboxID)
+	if err != nil {
+		return nil, err
+	}
+
+	return buildUnixSocketClient(socketAddress, timeout)
 }
 
 // buildUnixSocketClient build http client for Unix socket