Scheduling: Experimental bin packing algorithm.

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

scheduler/strategy/binpacking.go

@@ -0,0 +1,74 @@
+package strategy
+
+import (
+	"errors"
+	"sort"
+
+	"github.com/docker/libcluster"
+	"github.com/samalba/dockerclient"
+)
+
+var (
+	ErrNoResourcesAvailable = errors.New("no resources avaliable to schedule container")
+)
+
+type BinPackingPlacementStrategy struct {
+}
+
+func (p *BinPackingPlacementStrategy) PlaceContainer(config *dockerclient.ContainerConfig, nodes []*libcluster.Node) (*libcluster.Node, error) {
+	scores := scores{}
+
+	for _, node := range nodes {
+		// Skip nodes that are smaller than the requested resources.
+		if node.Memory < int64(config.Memory) || node.Cpus < config.CpuShares {
+			continue
+		}
+
+		var (
+			memory = int64(config.Memory)
+			cpus   = float64(config.CpuShares) / 100.0 * float64(node.Cpus)
+		)
+
+		var (
+			cpuScore    = ((node.ReservedCpus() + cpus) / float64(node.Cpus)) * 100.0
+			memoryScore = (float64(node.ReservedMemory()+memory) / float64(node.Memory)) * 100.0
+			total       = ((cpuScore + memoryScore) / 200.0) * 100.0
+		)
+
+		if cpuScore <= 100.0 && memoryScore <= 100.0 {
+			scores = append(scores, &score{node: node, score: total})
+		}
+	}
+
+	if len(scores) == 0 {
+		return nil, ErrNoResourcesAvailable
+	}
+
+	sort.Sort(scores)
+
+	return scores[0].node, nil
+}
+
+type score struct {
+	node  *libcluster.Node
+	score float64
+}
+
+type scores []*score
+
+func (s scores) Len() int {
+	return len(s)
+}
+
+func (s scores) Swap(i, j int) {
+	s[i], s[j] = s[j], s[i]
+}
+
+func (s scores) Less(i, j int) bool {
+	var (
+		ip = s[i]
+		jp = s[j]
+	)
+
+	return ip.score > jp.score
+}