Thick plugin should not wait for API readiness on CNI DEL

This modifies the behavior on CNI DEL for the thick plugin to just check once for API readiness, as opposed to waiting.

pkg/server/api/api.go

@@ -104,3 +104,12 @@ func WaitUntilAPIReady(socketPath string) error {
 		return err == nil, nil
 	})
 }
+
+// CheckAPIReadyNow checks API readiness once
+func CheckAPIReadyNow(socketPath string) error {
+	_, err := DoCNI(GetAPIEndpoint(MultusHealthAPIEndpoint), nil, SocketPath(socketPath))
+	if err != nil {
+		return fmt.Errorf("CheckAPIReadyNow: Daemon not reachable over socketfile: %v", err)
+	}
+	return nil
+}

pkg/server/api/shim.go

@@ -40,9 +40,12 @@ type ShimNetConf struct {
 	LogToStderr     bool   `json:"logToStderr,omitempty"`
 }
 
+// Define a type for API readiness check functions
+type APIReadyCheckFunc func(string) error
+
 // CmdAdd implements the CNI spec ADD command handler
 func CmdAdd(args *skel.CmdArgs) error {
-	response, cniVersion, err := postRequest(args)
+	response, cniVersion, err := postRequest(args, WaitUntilAPIReady)
 	if err != nil {
 		return logging.Errorf("CmdAdd (shim): %v", err)
 	}
@@ -53,7 +56,7 @@ func CmdAdd(args *skel.CmdArgs) error {
 
 // CmdCheck implements the CNI spec CHECK command handler
 func CmdCheck(args *skel.CmdArgs) error {
-	_, _, err := postRequest(args)
+	_, _, err := postRequest(args, WaitUntilAPIReady)
 	if err != nil {
 		return logging.Errorf("CmdCheck (shim): %v", err)
 	}
@@ -63,22 +66,22 @@ func CmdCheck(args *skel.CmdArgs) error {
 
 // CmdDel implements the CNI spec DEL command handler
 func CmdDel(args *skel.CmdArgs) error {
-	_, _, err := postRequest(args)
+	_, _, err := postRequest(args, CheckAPIReadyNow)
 	if err != nil {
 		// No error in DEL (as of CNI spec)
 		logging.Errorf("CmdDel (shim): %v", err)
 	}
 	return nil
 }
 
-func postRequest(args *skel.CmdArgs) (*Response, string, error) {
+func postRequest(args *skel.CmdArgs, readinessCheck APIReadyCheckFunc) (*Response, string, error) {
 	multusShimConfig, err := shimConfig(args.StdinData)
 	if err != nil {
 		return nil, "", fmt.Errorf("invalid CNI configuration passed to multus-shim: %w", err)
 	}
 
-	// check API readiness
-	if err := WaitUntilAPIReady(multusShimConfig.MultusSocketDir); err != nil {
+	// Execute the readiness check as necessary (e.g. don't wait on CNI DEL)
+	if err := readinessCheck(multusShimConfig.MultusSocketDir); err != nil {
 		return nil, multusShimConfig.CNIVersion, err
 	}