kube-applier fails at version check when using kubectl v1.28+

[jathinjd]

When CheckVersion executes at the beginning of the run, it expects the golang version to parse the output and determine the versions.

kube-applier/kube/client.go

Lines 80 to 107 in 5e4f51c

	func (c *Client) CheckVersion() error {
	args := []string{"kubectl", "version"}
	if c.LogLevel > -1 {
	args = append(args, fmt.Sprintf("-v=%d", c.LogLevel))
	}
	if c.Server != "" {
	args = append(args, fmt.Sprintf("--kubeconfig=%s", c.kubeconfigFilePath))
	}
	stdout, err := exec.Command(args[0], args[1:]...).CombinedOutput()
	output := strings.TrimSuffix(string(stdout), "\n")
	if err != nil {
	return fmt.Errorf("Error checking kubectl version: %v", output)
	}
	// Using regular expressions, parse for the Major and Minor version numbers for both client and server.
	clientPattern := regexp.MustCompile("(?:Client Version: version.Info{Major:\"([0-9+]+)\", Minor:\"([0-9+]+)\")")
	serverPattern := regexp.MustCompile("(?:Server Version: version.Info{Major:\"([0-9+]+)\", Minor:\"([0-9+]+)\")")
	clientInfo := clientPattern.FindAllStringSubmatch(output, -1)
	clientMajor := clientInfo[0][1]
	clientMinor := clientInfo[0][2]
	serverInfo := serverPattern.FindAllStringSubmatch(output, -1)
	serverMajor := serverInfo[0][1]
	serverMinor := serverInfo[0][2]
	return isCompatible(clientMajor, clientMinor, serverMajor, serverMinor)
	}

As of kubectl v1.28, the default output of kubectl version is what used to be for kubectl version --short.

After 1.28 upgrade:

2024/09/06 02:06:13 Output trimmed from kubectl version: Client Version: v1.28.13
Kustomize Version: v5.0.4-0.20230601165947-6ce0bf390ce3
Server Version: v1.28.11-gke.1260000

This causes kube-applier to fail with an index out of range error.