firecracker-orchestrator/main.go

// fc-orchestrator — Poor man's Firecracker snapshot orchestrator in Go.
//
// Creates a golden VM, snapshots it, then spawns N clones that share the
// base memory file via Firecracker's MAP_PRIVATE (kernel-level COW).
// Rootfs gets a filesystem-level COW copy (reflink where supported).
//
// Usage:
//
//	go build -o fc-orch .
//	sudo ./fc-orch init
//	sudo ./fc-orch golden
//	sudo ./fc-orch spawn 10
//	sudo ./fc-orch status
//	sudo ./fc-orch kill
//	sudo ./fc-orch cleanup
package main

import (
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"runtime"

	log "github.com/sirupsen/logrus"

	"github.com/kacerr/fc-orchestrator/orchestrator"
)

func main() {
	// strip --dev flag before subcommand routing
	dev := false
	filtered := os.Args[:1]
	for _, a := range os.Args[1:] {
		if a == "--dev" {
			dev = true
		} else {
			filtered = append(filtered, a)
		}
	}
	os.Args = filtered

	if dev {
		log.SetReportCaller(true)
		log.SetFormatter(&log.TextFormatter{
			CallerPrettyfier: func(f *runtime.Frame) (string, string) {
				return "", fmt.Sprintf("%s:%d", filepath.Base(f.File), f.Line)
			},
		})
	}

	// figure out if we are running as root
	if os.Geteuid() == 0 {
		fmt.Println("Running with root/sudo privileges!")
	} else {
		fmt.Println("Running as a normal user.")
	}

	if len(os.Args) < 2 {
		usage()
		os.Exit(1)
	}

	orch := orchestrator.New(orchestrator.DefaultConfig())

	switch os.Args[1] {
	case "init":
		fatal(orch.Init())
	case "golden":
		fatal(orch.Golden())
	case "spawn":
		n := 1
		if len(os.Args) > 2 {
			fmt.Sscanf(os.Args[2], "%d", &n)
		}
		fatal(orch.Spawn(n))
	case "status":
		orch.Status()
	case "kill":
		fatal(orch.Kill())
	case "cleanup":
		fatal(orch.Cleanup())
	case "console":
		if len(os.Args) < 3 {
			fmt.Fprintf(os.Stderr, "usage: %s console <id>\n", os.Args[0])
			os.Exit(1)
		}
		var id int
		fmt.Sscanf(os.Args[2], "%d", &id)
		fatal(orchestrator.ConnectConsole(orchestrator.DefaultConfig(), id))
	case "_console-proxy":
		// Internal subcommand: started by spawnOne, runs as a background daemon.
		fs := flag.NewFlagSet("_console-proxy", flag.ContinueOnError)
		var id int
		var tap string
		fs.IntVar(&id, "id", 0, "clone ID")
		fs.StringVar(&tap, "tap", "", "TAP device name")
		if err := fs.Parse(os.Args[2:]); err != nil {
			fmt.Fprintf(os.Stderr, "console-proxy: %v\n", err)
			os.Exit(1)
		}
		fatal(orchestrator.RunConsoleProxy(orchestrator.DefaultConfig(), id, tap))
	default:
		usage()
		os.Exit(1)
	}
}

func usage() {
	fmt.Fprintf(os.Stderr, `Usage: %s [--dev] <command> [args]

Flags:
  --dev         log format with source file:line (e.g. file="orchestrator.go:123")

Commands:
  init          Download kernel + create Alpine rootfs
  golden        Boot golden VM → pause → snapshot
  spawn [N]     Restore N clones from golden snapshot (default: 1)
  console <id>  Attach to the serial console of a running clone (Ctrl+] to detach)
  status        Show running clones
  kill          Kill all running VMs
  cleanup       Kill VMs + remove all state

Environment:
  FC_BIN          firecracker binary path  (default: firecracker)
  FC_BASE_DIR     working directory         (default: /tmp/fc-orch)
  FC_KERNEL       vmlinux path
  FC_KERNEL_URL   vmlinux download URL      (default: pinned Firecracker CI build)
  FC_ROOTFS       rootfs.ext4 path
  FC_VCPUS        vCPUs per VM              (default: 1)
  FC_MEM_MIB      MiB per VM                (default: 128)
  FC_BRIDGE       bridge name or "none"     (default: fcbr0)
`, os.Args[0])
}

func fatal(err error) {
	if err != nil {
		fmt.Fprintf(os.Stderr, "fatal: %v\n", err)
		os.Exit(1)
	}
}