Label filter: Support for node pinning by name or id.

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

scheduler/filter/label.go

@@ -29,10 +29,19 @@ func (f *LabelFilter) Filter(config *dockerclient.ContainerConfig, nodes []*clus
 	for k, v := range constraints {
 		candidates := []*cluster.Node{}
 		for _, node := range nodes {
-			if label, ok := node.Labels[k]; ok {
-				if strings.Contains(strings.ToLower(label), v) {
+			switch k {
+			case "node":
+				// "node" label is a special case pinning a container to a specific node.
+				if strings.ToLower(node.ID) == v || strings.ToLower(node.Name) == v {
 					candidates = append(candidates, node)
 				}
+			default:
+				// By default match the node labels.
+				if label, ok := node.Labels[k]; ok {
+					if strings.Contains(strings.ToLower(label), v) {
+						candidates = append(candidates, node)
+					}
+				}
 			}
 		}
 		if len(candidates) == 0 {

scheduler/filter/label_test.go

@@ -12,24 +12,30 @@ func TestLabeleFilter(t *testing.T) {
 	var (
 		f     = LabelFilter{}
 		nodes = []*cluster.Node{
+			cluster.NewNode("node-0"),
 			cluster.NewNode("node-1"),
 			cluster.NewNode("node-2"),
-			cluster.NewNode("node-3"),
 		}
 		result []*cluster.Node
 		err    error
 	)
 
+	nodes[0].ID = "node-0-id"
+	nodes[0].Name = "node-0-name"
 	nodes[0].Labels = map[string]string{
 		"name":  "node0",
 		"group": "1",
 	}
 
+	nodes[1].ID = "node-1-id"
+	nodes[1].Name = "node-1-name"
 	nodes[1].Labels = map[string]string{
 		"name":  "node1",
 		"group": "1",
 	}
 
+	nodes[2].ID = "node-2-id"
+	nodes[2].Name = "node-2-name"
 	nodes[2].Labels = map[string]string{
 		"name":  "node2",
 		"group": "2",
@@ -62,6 +68,22 @@ func TestLabeleFilter(t *testing.T) {
 	assert.Len(t, result, 2)
 	assert.NotContains(t, result, nodes[2])
 
+	// Validate node pinning by id.
+	result, err = f.Filter(&dockerclient.ContainerConfig{
+		Env: []string{"constraint:node=node-2-id"},
+	}, nodes)
+	assert.NoError(t, err)
+	assert.Len(t, result, 1)
+	assert.Equal(t, result[0], nodes[2])
+
+	// Validate node pinning by name.
+	result, err = f.Filter(&dockerclient.ContainerConfig{
+		Env: []string{"constraint:node=node-1-name"},
+	}, nodes)
+	assert.NoError(t, err)
+	assert.Len(t, result, 1)
+	assert.Equal(t, result[0], nodes[1])
+
 	// Make sure constraints are evaluated as logical ANDs.
 	result, err = f.Filter(&dockerclient.ContainerConfig{
 		Env: []string{"constraint:name=node0", "constraint:group=1"},