Docker Swarm程式碼分析筆記（14）——strategy

這是一個建立於 的文章，其中的資訊可能已經有所發展或是發生改變。

Docker Swarm manage命令的flStrategy選項用來指定scheduler調度的strategy的過濾項，其變數定義如下（cli/flags.go）：

flStrategy = cli.StringFlag{    Name:  "strategy",    Usage: "placement strategy to use [" + strings.Join(strategy.List(), ", ") + "]",    Value: strategy.List()[0],}

strategy的預設值是SpreadPlacementStrategy。

strategy在代碼中的實際定義是PlacementStrategy，一個interface：

// PlacementStrategy is the interface for a container placement strategy.type PlacementStrategy interface {    // Name of the strategy    Name() string    // Initialize performs any initial configuration required by the strategy and returns    // an error if one is encountered.    // If no initial configuration is needed, this may be a no-op and return a nil error.    Initialize() error    // RankAndSort applies the strategy to a list of nodes and ranks them based    // on the best fit given the container configuration.  It returns a sorted    // list of nodes (based on their ranks) or an error if there is no    // available node on which to schedule the container.    RankAndSort(config *cluster.ContainerConfig, nodes []*node.Node) ([]*node.Node, error)}

其中RankAndSort返回一個符合條件node（也就是Docker Engine）列表，列表中元素按匹配度排序。