Docker Swarm代码分析笔记(9)——Swarm的Cluster,Engine和addEngine

swarm/cluster.go属于swarm这个package,它定义了swarm这个driver的Cluster结构体:

// Cluster is exported
type Cluster struct {
 sync.RWMutex
 eventHandlers *cluster.EventHandlers
 engines map[string]*cluster.Engine
 pendingEngines map[string]*cluster.Engine
 scheduler *scheduler.Scheduler
 discovery discovery.Backend
 pendingContainers map[string]*pendingContainer
 overcommitRatio float64
 engineOpts *cluster.EngineOpts
 createRetry int64
 TLSConfig *tls.Config
}

其中很重要的是cluster.Engine这个结构体的定义(cluster/engine.go),每个cluster.Engine代表一个Docker engine,即Docker daemon:

// Engine represents a docker engine
type Engine struct {
 sync.RWMutex
 ID string
 IP string
 Addr string
 Name string
 Cpus int64
 Memory int64
 Labels map[string]string
 Version string
 stopCh chan struct{}
 refreshDelayer *delayer
 containers map[string]*Container
 images []*Image
 networksmap[string]*Network
 volumes map[string]*Volume
 client dockerclient.Client
 apiClient engineapi.APIClient
 eventHandlerEventHandler
 state engineState
 lastError string
 updatedAt time.Time
 failureCountint
 overcommitRatio int64
 opts*EngineOpts
 eventsMonitor *EventsMonitor
}

创建cluster最核心的部分就是addEngine这个方法,即把Docker engine加到cluster中:

func (c *Cluster) addEngine(addr string) bool {
 // Check the engine is already registered by address.
 if c.hasEngineByAddr(addr) {
 return false
 }
 engine := cluster.NewEngine(addr, c.overcommitRatio, c.engineOpts)
 if err := engine.RegisterEventHandler(c); err != nil {
 log.Error(err)
 }
 // Add it to pending engine map, indexed by address. This will prevent
 // duplicates from entering
 c.Lock()
 c.pendingEngines[addr] = engine
 c.Unlock()
 // validatePendingEngine will start a thread to validate the engine.
 // If the engine is reachable and valid, it'll be monitored and updated in a loop.
 // If engine is not reachable, pending engines will be examined once in a while
 go c.validatePendingEngine(engine)
 return true
}

addEngine首先检查当前engine是否已经存在cluster中,如果没有则会分配一个新的engine,同时把它先加到Cluster.pendingEngines中,并启动一个新的goroutine(validatePendingEngine)去检查它是否是个有效的engine。

另外,Engine.RegisterEventHandler实质上就是把Cluster的eventHandlers成员赋给Engine.eventHandler:

// RegisterEventHandler registers an event handler.
func (e *Engine) RegisterEventHandler(h EventHandler) error {
 if e.eventHandler != nil {
 return errors.New("event handler already set")
 }
 e.eventHandler = h
 return nil
}

而Cluster的eventHandlers则是在NewPrimary中赋值的,所以本质上Engine和Cluster用的都是一套处理函数。

有疑问加站长微信联系(非本文作者)

• 请尽量让自己的回复能够对别人有帮助
• 支持 Markdown 格式, **粗体**、~~删除线~~、`单行代码`
• 支持 @ 本站用户;支持表情(输入 : 提示),见 Emoji cheat sheet
• 图片支持拖拽、截图粘贴等方式上传