Initial push

2026-08-11 09:00:01 +02:00
commit fe8b354adc
54 changed files with 12640 additions and 0 deletions
@@ -0,0 +1,257 @@
+// Command docker-migrate moves Docker containers, together with their volumes
+// and bind mounts, from one host to another.
+//
+// It runs either as a web application (the default) or as a one-shot inventory
+// dump for scripting. It needs no agent on the target: everything is driven
+// through the target's own docker CLI over SSH, or through a self-contained
+// package that is carried to the target by hand.
+package main
+
+import (
+	"context"
+	"crypto/rand"
+	"encoding/hex"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"log/slog"
+	"net"
+	"net/http"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"runtime"
+	"strings"
+	"syscall"
+	"time"
+
+	"github.com/arescom/docker-migrate/internal/api"
+	"github.com/arescom/docker-migrate/internal/dkr"
+	"github.com/arescom/docker-migrate/internal/webui"
+)
+
+// version is overridden at build time with -ldflags "-X main.version=...".
+var version = "dev"
+
+func main() {
+	if err := run(os.Args[1:]); err != nil {
+		if errors.Is(err, flag.ErrHelp) {
+			os.Exit(2)
+		}
+		fmt.Fprintln(os.Stderr, "error: "+err.Error())
+		os.Exit(1)
+	}
+}
+
+func run(args []string) error {
+	cmd := "serve"
+	if len(args) > 0 && !strings.HasPrefix(args[0], "-") {
+		cmd, args = args[0], args[1:]
+	}
+	switch cmd {
+	case "serve":
+		return serve(args)
+	case "inspect":
+		return inspect(args)
+	case "version":
+		fmt.Printf("docker-migrate %s (%s %s/%s)\n", version, runtime.Version(), runtime.GOOS, runtime.GOARCH)
+		return nil
+	case "help", "-h", "--help":
+		usage()
+		return nil
+	default:
+		usage()
+		return fmt.Errorf("unknown command %q", cmd)
+	}
+}
+
+func usage() {
+	fmt.Fprint(os.Stderr, `docker-migrate - move Docker containers and their data between hosts
+
+Usage:
+  docker-migrate [serve] [flags]   start the web interface (default)
+  docker-migrate inspect [flags]   print the source inventory as JSON
+  docker-migrate version           print the version
+
+Run "docker-migrate serve -h" for the server flags.
+`)
+}
+
+func serve(args []string) error {
+	fs := flag.NewFlagSet("serve", flag.ContinueOnError)
+	addr := fs.String("addr", "127.0.0.1:8080", "address to listen on; use 0.0.0.0:8080 to expose it on the network")
+	token := fs.String("token", "", "require this token on every request; \"auto\" generates one")
+	dataDir := fs.String("data-dir", defaultDataDir(), "directory for connections and trusted host keys")
+	pkgDir := fs.String("package-dir", "", "directory for migration packages (default <data-dir>/packages)")
+	dockerHost := fs.String("docker-host", "", "source docker daemon (default: the DOCKER_HOST environment)")
+	verbose := fs.Bool("v", false, "verbose logging")
+	fs.Usage = func() {
+		fmt.Fprintln(os.Stderr, "Usage: docker-migrate serve [flags]\n\nFlags:")
+		fs.PrintDefaults()
+	}
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+
+	level := slog.LevelInfo
+	if *verbose {
+		level = slog.LevelDebug
+	}
+	logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{Level: level}))
+
+	authToken := *token
+	if authToken == "auto" {
+		authToken = randomToken()
+	}
+	// Anything but a loopback bind is reachable by other machines. This tool
+	// can stop containers and read every volume on the host, so it refuses to
+	// be exposed without a token.
+	if authToken == "" && !isLoopback(*addr) {
+		authToken = randomToken()
+		logger.Warn("listening on a non-loopback address; generated an access token")
+	}
+
+	cfg := api.Config{
+		Addr:       *addr,
+		Token:      authToken,
+		DataDir:    *dataDir,
+		PackageDir: *pkgDir,
+		DockerHost: *dockerHost,
+		UI:         webui.FS(),
+		Logger:     logger,
+	}
+	srv, err := api.New(cfg)
+	if err != nil {
+		return err
+	}
+	defer srv.Close()
+
+	if !webui.Built() {
+		logger.Warn("web UI is not embedded in this binary; only the HTTP API is available")
+	}
+
+	httpSrv := &http.Server{
+		Addr:              *addr,
+		Handler:           srv.Handler(),
+		ReadHeaderTimeout: 15 * time.Second,
+		// Migrations stream for as long as the data takes; no write timeout.
+		IdleTimeout: 120 * time.Second,
+	}
+
+	ln, err := net.Listen("tcp", *addr)
+	if err != nil {
+		return fmt.Errorf("listen on %s: %w", *addr, err)
+	}
+
+	url := "http://" + displayAddr(ln.Addr().String())
+	if authToken != "" {
+		url += "/?token=" + authToken
+	}
+	fmt.Fprintf(os.Stderr, "\n  docker-migrate %s\n  open %s\n  data: %s\n\n", version, url, *dataDir)
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
+	errCh := make(chan error, 1)
+	go func() {
+		if err := httpSrv.Serve(ln); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			errCh <- err
+		}
+	}()
+
+	select {
+	case err := <-errCh:
+		return err
+	case <-ctx.Done():
+		logger.Info("shutting down")
+		shutdownCtx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
+		defer cancel()
+		return httpSrv.Shutdown(shutdownCtx)
+	}
+}
+
+func inspect(args []string) error {
+	fs := flag.NewFlagSet("inspect", flag.ContinueOnError)
+	dockerHost := fs.String("docker-host", "", "docker daemon to read (default: the DOCKER_HOST environment)")
+	sizes := fs.Bool("sizes", false, "also measure volume sizes (slower)")
+	fs.Usage = func() {
+		fmt.Fprintln(os.Stderr, "Usage: docker-migrate inspect [flags]\n\nFlags:")
+		fs.PrintDefaults()
+	}
+	if err := fs.Parse(args); err != nil {
+		return err
+	}
+
+	c, err := dkr.New(*dockerHost)
+	if err != nil {
+		return err
+	}
+	defer c.Close()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Minute)
+	defer cancel()
+
+	inv, err := c.Inventory(ctx)
+	if err != nil {
+		return err
+	}
+	if *sizes {
+		if err := c.MeasureMounts(ctx, inv.Containers); err != nil {
+			fmt.Fprintln(os.Stderr, "warning: could not measure volume sizes: "+err.Error())
+		}
+	}
+	enc := json.NewEncoder(os.Stdout)
+	enc.SetIndent("", "  ")
+	return enc.Encode(inv)
+}
+
+// defaultDataDir picks a per-user location, honouring the container-friendly
+// DOCKER_MIGRATE_DATA override.
+func defaultDataDir() string {
+	if v := os.Getenv("DOCKER_MIGRATE_DATA"); v != "" {
+		return v
+	}
+	if dir, err := os.UserConfigDir(); err == nil {
+		return filepath.Join(dir, "docker-migrate")
+	}
+	return ".docker-migrate"
+}
+
+func randomToken() string {
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		return fmt.Sprintf("t%d", time.Now().UnixNano())
+	}
+	return hex.EncodeToString(b)
+}
+
+func isLoopback(addr string) bool {
+	host, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		return false
+	}
+	if host == "" {
+		return false // an empty host binds every interface
+	}
+	if host == "localhost" {
+		return true
+	}
+	ip := net.ParseIP(host)
+	return ip != nil && ip.IsLoopback()
+}
+
+// displayAddr turns a wildcard bind into something clickable.
+func displayAddr(addr string) string {
+	host, port, err := net.SplitHostPort(addr)
+	if err != nil {
+		return addr
+	}
+	if host == "" || host == "0.0.0.0" || host == "::" {
+		return "localhost:" + port
+	}
+	if strings.Contains(host, ":") {
+		return "[" + host + "]:" + port
+	}
+	return host + ":" + port
+}