metropolis/node/kubernetes/hyperkube/main.go

// Copyright The Monogon Project Authors.
// SPDX-License-Identifier: Apache-2.0

// This is the entry point for our multicall Kubernetes binary. It can act as
// any of the Kubernetes components we use depending on its first argument.
// This saves us a bunch of duplicated code and thus system partition size as
// a large amount of library code is shared between all of the Kubernetes
// components.
//
// As this is not intended by the K8s developers the Cobra setup is unusual
// in that even the command structs are only created on-demand and not
// registered with AddCommand. This is done as Kubernetes performs one-off
// global setup inside their NewXYZCommand functions, for example for signal
// handling and their global registries.
package main

import (
	"context"
	"fmt"
	"os"

	"github.com/spf13/cobra"
	"k8s.io/component-base/cli"
	_ "k8s.io/component-base/metrics/prometheus/restclient" // for client metric registration
	_ "k8s.io/component-base/metrics/prometheus/version"    // for version metric registration
	kubeapiserver "k8s.io/kubernetes/cmd/kube-apiserver/app"
	kubecontrollermanager "k8s.io/kubernetes/cmd/kube-controller-manager/app"
	kubescheduler "k8s.io/kubernetes/cmd/kube-scheduler/app"
	kubelet "k8s.io/kubernetes/cmd/kubelet/app"
)

// Map of subcommand to Cobra command generator for all subcommands
var subcommands = map[string]func() *cobra.Command{
	"kube-apiserver":          kubeapiserver.NewAPIServerCommand,
	"kube-controller-manager": kubecontrollermanager.NewControllerManagerCommand,
	"kube-scheduler":          func() *cobra.Command { return kubescheduler.NewSchedulerCommand() },
	"kubelet":                 func() *cobra.Command { return kubelet.NewKubeletCommand(context.Background()) },
}

func main() {
	if len(os.Args) < 2 || subcommands[os.Args[1]] == nil {
		fmt.Fprintf(os.Stderr, "Unknown subcommand\n")
	} else {
		cmdGen := subcommands[os.Args[1]]
		cmd := cmdGen()
		// Strip first argument as it has already been consumed
		cmd.SetArgs(os.Args[2:])
		os.Exit(cli.Run(cmd))
	}
}