Flux Exec (fluxexec)

Introduction

This package provides a wrapper of the command line interface to execute Flux commands.

How to add new flags

Add the new type Option struct to the options.go of fluxexec package. Then create a function to represent it.

The below example shows how to add the --export flag. We have ExportOption struct to whole the value of the --export flag, and we have Export function to represent this flag during the command creation.

type ExportOption struct {
	export bool
}

// Export represents the --export flag.
func Export(export bool) *ExportOption {
	return &ExportOption{export}
}

After that we go to each command wrapper file, for example we have install.go file as the wrapper of flux install command, and we have bootstrap_github.go file as the wrapper of the flux bootstrap github command.

Following the above example, we add the --export flag to the wrapper of the install command.

First, find the installConfig struct in the install.go file. Then, add the export field to the struct.

type installConfig struct {
	clusterDomain      string
	components         []string
	componentsExtra    []string
	export             bool     // Here's our new export field
	imagePullSecret    string
	logLevel           string
	networkPolicy      bool
	registry           string
	tolerationKeys     []string
	watchAllNamespaces bool
}

Then, we add the configureInstall function for the ExportOption struct. This function will be called to configure the installConfig struct, by setting the value of the export field.

func (opt *ExportOption) configureInstall(conf *installConfig) {
	conf.export = opt.export
}

Next, locate the installCmd function.

func (flux *Flux) installCmd(ctx context.Context, opts ...InstallOption) (*exec.Cmd, error) {

This function will be called to create the command, with all the flags as args. We add the following if statement to help this command generate the --export flag.

	if c.export && !reflect.DeepEqual(c.export, defaultInstallOptions.export) {
		args = append(args, "--export")
	}

Revisiting the package for a new Flux version

When a new version of Flux is released, the fluxexec package needs to be revisited to ensure that all the new flags are added. To do so, we need to check the flux install and flux bootstrap commands to see if there are any new flags added.

For example, running the following command to check if there's a new default value: flux install --help | grep "(default"

$ flux install --help | grep "(default"
      --cluster-domain string      internal cluster domain (default "cluster.local")
      --components strings         list of components, accepts comma-separated values (default [source-controller,kustomize-controller,helm-controller,notification-controller])
      --log-level logLevel         log level, available options are: (debug, info, error) (default info)
      --network-policy             deny ingress access to the toolkit controllers from other namespaces using network policies (default true)
      --registry string            container registry where the toolkit images are published (default "ghcr.io/fluxcd")
      --watch-all-namespaces       watch for custom resources in all namespaces, if set to false it will only watch the namespace where the toolkit is installed (default true)

Here's the new flags from the global scope in the flux install command.

      --cache-dir string               Default cache directory (default "/home/user/.kube/cache")
      --kube-api-burst int             The maximum burst queries-per-second of requests sent to the Kubernetes API. (default 100)
      --kube-api-qps float32           The maximum queries-per-second of requests sent to the Kubernetes API. (default 50)
  -n, --namespace string               If present, the namespace scope for this CLI request (default "flux-system")
      --timeout duration               timeout for this operation (default 5m0s)

Future Improvements

The current implementation of the fluxexec package is not ideal. It is not easy to add new flags, and it is not easy to maintain. We need to find a better way to implement this package. For example, we would write a script to generate the code of this package for us, instead of writing the code manually. It would be done by parsing the flux install and flux bootstrap commands, and generate the code based on the flags.