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strategy

binpack

binpack策略就是为了避免容器碎片化，意味着将容器尽可能的分配到一个节点上(这样说可能不准确，也就是把资源集中起来，预留出更多闲置的资源)，预留出未使用的节点给需要更大空间的容器运行。
这段源码位于swarm/scheduler/strategy.go/binpack.go

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// BinpackPlacementStrategy places a container onto the most packed node in the cluster.
//空结构体
type BinpackPlacementStrategy struct {
}

// Initialize a BinpackPlacementStrategy.
func (p *BinpackPlacementStrategy) Initialize() error {
	return nil
}

// Name returns the name of the strategy.
func (p *BinpackPlacementStrategy) Name() string {
	return "binpack"
}

上面用于初始化一个空结构体

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// RankAndSort sorts nodes based on the binpack strategy applied to the container config.
func (p *BinpackPlacementStrategy) RankAndSort(config *cluster.ContainerConfig, nodes []*node.Node) ([]*node.Node, error) {
	// for binpack, a healthy node should increase its weight to increase its chance of being selected
	// set healthFactor to 10 to make health degree [0, 100] overpower cpu + memory (each in range [0, 100])
	const healthFactor int64 = 10
	//返回满足条件的节点群，对于节点打上不同的分数(根据cpu，mem和节点健康因子)
	weightedNodes, err := weighNodes(config, nodes, healthFactor)
	if err != nil {
		return nil, err
	}

	sort.Sort(sort.Reverse(weightedNodes))
	output := make([]*node.Node, len(weightedNodes))
	for i, n := range weightedNodes {
		output[i] = n.Node
	}
	return output, nil
}

weighNodes函数作用:读取要启动的容器的配置，接着扫描集群中所有的节点，过滤掉那些cpu或者内存不满足的节点，并对满足条件的节点从三个方面进行考核(cpu,mem和节点的健康状况)进行打分，满分一百，组成一个候选队列，从队列中返回三项加起来最大的节点。

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//weighted_node.go
func weighNodes(config *cluster.ContainerConfig, nodes []*node.Node, healthinessFactor int64) (weightedNodeList, error) {
	weightedNodes := weightedNodeList{}
	//遍历找寻合适的节点(cpu，内存合适的节点)
	for _, node := range nodes {
		nodeMemory := node.TotalMemory
		nodeCpus := node.TotalCpus

		// Skip nodes that are smaller than the requested resources.
		if nodeMemory < int64(config.HostConfig.Memory) || nodeCpus < config.HostConfig.CPUShares {
			continue
		}

		var (
			cpuScore    int64 = 100
			memoryScore int64 = 100
		)

		if config.HostConfig.CPUShares > 0 {
			cpuScore = (node.UsedCpus + config.HostConfig.CPUShares) * 100 / nodeCpus
		}
		if config.HostConfig.Memory > 0 {
			memoryScore = (node.UsedMemory + config.HostConfig.Memory) * 100 / nodeMemory
		}

		if cpuScore <= 100 && memoryScore <= 100 {
			weightedNodes = append(weightedNodes, &weightedNode{Node: node, Weight: cpuScore + memoryScore + healthinessFactor*node.HealthIndicator})
		}
	}

	if len(weightedNodes) == 0 {
		return nil, ErrNoResourcesAvailable
	}

	return weightedNodes, nil
}