docker后台服务的主要实现在runtime.go中。因此梳理玩docker启动逻辑之后，我们来看看runtime的实现。
runtime中主要包含runtime和history的实现。
初始化
// 存储系统初始化路径
var sysInitPath string
func init() {
//# `SelfPath`是`docker`的绝对路径，具体参见`docker.go`。
sysInitPath = SelfPath()
runtime
runtime的构造
type Runtime struct {
root string
//# 运行环境仓库`path.Join(root, "containers")`
repository string
//# 容器列表
containers *list.List
//# 网络
networkManager *NetworkManager
//# 本地存储
graph *Graph
//# `images`仓库
repositories *TagStore
//# 权限配置
authConfig *auth.AuthConfig
}
runtime的方法
//# List 遍历`runtime.containers`, 生成`history`返回。
func (runtime *Runtime) List() []*Container {
containers := new(History)
for e := runtime.containers.Front(); e != nil; e = e.Next() {
containers.Add(e.Value.(*Container))
}
return *containers
}
func (runtime *Runtime) getContainerElement(id string) *list.Element {
for e := runtime.containers.Front(); e != nil; e = e.Next() {
container := e.Value.(*Container)
if container.Id == id {
return e
}
}
return nil
}
//# Get 调用`getContainerElement`遍历`runtime.containers`根据id找出`container`。不存在返回nil, 存在返回`Container`的指针。
func (runtime *Runtime) Get(id string) *Container {
e := runtime.getContainerElement(id)
if e == nil {
return nil
}
return e.Value.(*Container)
}
//# Exists 判断id对应的`Container`是否存在
func (runtime *Runtime) Exists(id string) bool {
return runtime.Get(id) != nil
}
func (runtime *Runtime) containerRoot(id string) string {
return path.Join(runtime.repository, id)
}
//# Create 创建一个容器
func (runtime *Runtime) Create(config *Config) (*Container, error) {
// 查找`Image`
img, err := runtime.repositories.LookupImage(config.Image)
if err != nil {
return nil, err
}
container := &Container{
// FIXME: we should generate the ID here instead of receiving it as an argument
Id: GenerateId(),
Created: time.Now(),
Path: config.Cmd[0],
Args: config.Cmd[1:], //FIXME: de-duplicate from config
Config: config,
Image: img.Id, // Always use the resolved image id
NetworkSettings: &NetworkSettings{},
// FIXME: do we need to store this in the container?
SysInitPath: sysInitPath,
}
container.root = runtime.containerRoot(container.Id)
//# 第1步：创建容器目录。
// 同时还可以避免出现竞态条件。
if err := os.Mkdir(container.root, 0700); err != nil {
return nil, err
}
//# 第2步：保存容器JSON
if err := container.ToDisk(); err != nil {
return nil, err
}
//# 第3步：注册容器
if err := runtime.Register(container); err != nil {
return nil, err
}
return container, nil
}
func (runtime *Runtime) Load(id string) (*Container, error) {
container := &Container{root: runtime.containerRoot(id)}
if err := container.FromDisk(); err != nil {
return nil, err
}
if container.Id != id {
return container, fmt.Errorf("Container %s is stored at %s", container.Id, id)
}
if err := runtime.Register(container); err != nil {
return nil, err
}
return container, nil
}
// Register makes a container object usable by the runtime as <container.Id>
func (runtime *Runtime) Register(container *Container) error {
if container.runtime != nil || runtime.Exists(container.Id) {
return fmt.Errorf("Container is already loaded")
}
if err := validateId(container.Id); err != nil {
return err
}
container.runtime = runtime
// Setup state lock (formerly in newState()
lock := new(sync.Mutex)
container.State.stateChangeLock = lock
container.State.stateChangeCond = sync.NewCond(lock)
// Attach to stdout and stderr
container.stderr = newWriteBroadcaster()
container.stdout = newWriteBroadcaster()
// Attach to stdin
if container.Config.OpenStdin {
container.stdin, container.stdinPipe = io.Pipe()
} else {
container.stdinPipe = NopWriteCloser(ioutil.Discard) // Silently drop stdin
}
// Setup logging of stdout and stderr to disk
if err := runtime.LogToDisk(container.stdout, container.logPath("stdout")); err != nil {
return err
}
if err := runtime.LogToDisk(container.stderr, container.logPath("stderr")); err != nil {
return err
}
// done
runtime.containers.PushBack(container)
return nil
}
func (runtime *Runtime) LogToDisk(src *writeBroadcaster, dst string) error {
log, err := os.OpenFile(dst, os.O_RDWR|os.O_APPEND|os.O_CREATE, 0600)
if err != nil {
return err
}
src.AddWriter(NopWriteCloser(log))
return nil
}
func (runtime *Runtime) Destroy(container *Container) error {
element := runtime.getContainerElement(container.Id)
if element == nil {
return fmt.Errorf("Container %v not found - maybe it was already destroyed?", container.Id)
}
if err := container.Stop(); err != nil {
return err
}
if mounted, err := container.Mounted(); err != nil {
return err
} else if mounted {
if err := container.Unmount(); err != nil {
return fmt.Errorf("Unable to unmount container %v: %v", container.Id, err)
}
}
// Deregister the container before removing its directory, to avoid race conditions
runtime.containers.Remove(element)
if err := os.RemoveAll(container.root); err != nil {
return fmt.Errorf("Unable to remove filesystem for %v: %v", container.Id, err)
}
return nil
}
// Commit creates a new filesystem image from the current state of a container.
// The image can optionally be tagged into a repository
func (runtime *Runtime) Commit(id, repository, tag string) (*Image, error) {
container := runtime.Get(id)
if container == nil {
return nil, fmt.Errorf("No such container: %s", id)
}
// FIXME: freeze the container before copying it to avoid data corruption?
// FIXME: this shouldn't be in commands.
rwTar, err := container.ExportRw()
if err != nil {
return nil, err
}
// Create a new image from the container's base layers + a new layer from container changes
img, err := runtime.graph.Create(rwTar, container, "")
if err != nil {
return nil, err
}
// Register the image if needed
if repository != "" {
if err := runtime.repositories.Set(repository, tag, img.Id, true); err != nil {
return img, err
}
}
return img, nil
}
func (runtime *Runtime) restore() error {
dir, err := ioutil.ReadDir(runtime.repository)
if err != nil {
return err
}
for _, v := range dir {
id := v.Name()
container, err := runtime.Load(id)
if err != nil {
Debugf("Failed to load container %v: %v", id, err)
continue
}
Debugf("Loaded container %v", container.Id)
}
return nil
}
history
history的构造
//# 历史记录是一个存储`Container`指针的数组。`Contatiner`结构体将在`container.go`中详细介绍。
type History []*Container
history的方法
func (history *History) Len() int {
return len(*history)
}
func (history *History) Less(i, j int) bool {
containers := *history
return containers[j].When().Before(containers[i].When())
}
func (history *History) Swap(i, j int) {
containers := *history
tmp := containers[i]
containers[i] = containers[j]
containers[j] = tmp
}
func (history *History) Add(container *Container) {
*history = append(*history, container)
sort.Sort(history)
}