blob: ec880b9c85d7ba71948d8e3a97fd5c477799045e [file] [log] [blame]
package engine
import (
type Handler func(*Job) Status
var globalHandlers map[string]Handler
func init() {
globalHandlers = make(map[string]Handler)
func Register(name string, handler Handler) error {
_, exists := globalHandlers[name]
if exists {
return fmt.Errorf("Can't overwrite global handler for command %s", name)
globalHandlers[name] = handler
return nil
// The Engine is the core of Docker.
// It acts as a store for *containers*, and allows manipulation of these
// containers by executing *jobs*.
type Engine struct {
root string
handlers map[string]Handler
hack Hack // data for temporary hackery (see hack.go)
id string
Stdout io.Writer
Stderr io.Writer
Stdin io.Reader
func (eng *Engine) Root() string {
return eng.root
func (eng *Engine) Register(name string, handler Handler) error {
_, exists := eng.handlers[name]
if exists {
return fmt.Errorf("Can't overwrite handler for command %s", name)
eng.handlers[name] = handler
return nil
// New initializes a new engine managing the directory specified at `root`.
// `root` is used to store containers and any other state private to the engine.
// Changing the contents of the root without executing a job will cause unspecified
// behavior.
func New(root string) (*Engine, error) {
// Check for unsupported architectures
if runtime.GOARCH != "amd64" {
return nil, fmt.Errorf("The docker runtime currently only supports amd64 (not %s). This will change in the future. Aborting.", runtime.GOARCH)
// Check for unsupported kernel versions
// FIXME: it would be cleaner to not test for specific versions, but rather
// test for specific functionalities.
// Unfortunately we can't test for the feature "does not cause a kernel panic"
// without actually causing a kernel panic, so we need this workaround until
// the circumstances of pre-3.8 crashes are clearer.
// For details see
if k, err := utils.GetKernelVersion(); err != nil {
log.Printf("WARNING: %s\n", err)
} else {
if utils.CompareKernelVersion(k, &utils.KernelVersionInfo{Kernel: 3, Major: 8, Minor: 0}) < 0 {
if os.Getenv("DOCKER_NOWARN_KERNEL_VERSION") == "" {
log.Printf("WARNING: You are running linux kernel version %s, which might be unstable running docker. Please upgrade your kernel to 3.8.0.", k.String())
if err := os.MkdirAll(root, 0700); err != nil && !os.IsExist(err) {
return nil, err
// Docker makes some assumptions about the "absoluteness" of root
// ... so let's make sure it has no symlinks
if p, err := filepath.Abs(root); err != nil {
log.Fatalf("Unable to get absolute root (%s): %s", root, err)
} else {
root = p
if p, err := filepath.EvalSymlinks(root); err != nil {
log.Fatalf("Unable to canonicalize root (%s): %s", root, err)
} else {
root = p
eng := &Engine{
root: root,
handlers: make(map[string]Handler),
id: utils.RandomString(),
Stdout: os.Stdout,
Stderr: os.Stderr,
Stdin: os.Stdin,
// Copy existing global handlers
for k, v := range globalHandlers {
eng.handlers[k] = v
return eng, nil
func (eng *Engine) String() string {
return fmt.Sprintf("%s|%s", eng.Root(),[:8])
// Job creates a new job which can later be executed.
// This function mimics `Command` from the standard os/exec package.
func (eng *Engine) Job(name string, args ...string) *Job {
job := &Job{
Eng: eng,
Name: name,
Args: args,
Stdin: NewInput(),
Stdout: NewOutput(),
Stderr: NewOutput(),
env: &Env{},
handler, exists := eng.handlers[name]
if exists {
job.handler = handler
return job
func (eng *Engine) Logf(format string, args ...interface{}) (n int, err error) {
if os.Getenv("TEST") == "" {
prefixedFormat := fmt.Sprintf("[%s] %s\n", eng, strings.TrimRight(format, "\n"))
return fmt.Fprintf(eng.Stderr, prefixedFormat, args...)
return 0, nil