Support constraint on platform architecture and OS.

Signed-off-by: Dong Chen <dongluo.chen@docker.com>

README.md

@@ -56,6 +56,8 @@ Some of *SwarmKit*'s main features are:
         | node.id | node's ID | `node.id == 2ivku8v2gvtg4`|
         | node.hostname | node's hostname | `node.hostname != node-2`|
         | node.role |  node's manager or worker role | `node.role == manager`|
+        | node.platform.os |  node's operating system | `node.platform.os == linux`|
+        | node.platform.arch |  node's architecture | `node.platform.arch == x86_64`|
         | node.labels | node's labels added by cluster admins | `node.labels.security == high`|
         | engine.labels | Docker Engine's labels | `engine.labels.operatingsystem == ubuntu 14.04`|
 

manager/constraint/constraint.go

@@ -125,6 +125,26 @@ func NodeMatches(constraints []Constraint, n *api.Node) bool {
 			if !constraint.Match(n.Spec.Role.String()) {
 				return false
 			}
+		case strings.EqualFold(constraint.key, "node.platform.os"):
+			if n.Description == nil || n.Description.Platform == nil {
+				if !constraint.Match("") {
+					return false
+				}
+				continue
+			}
+			if !constraint.Match(n.Description.Platform.OS) {
+				return false
+			}
+		case strings.EqualFold(constraint.key, "node.platform.arch"):
+			if n.Description == nil || n.Description.Platform == nil {
+				if !constraint.Match("") {
+					return false
+				}
+				continue
+			}
+			if !constraint.Match(n.Description.Platform.Architecture) {
+				return false
+			}
 
 		// node labels constraint in form like 'node.labels.key==value'
 		case len(constraint.key) > len(nodeLabelPrefix) && strings.EqualFold(constraint.key[:len(nodeLabelPrefix)], nodeLabelPrefix):

manager/scheduler/constraint_test.go

@@ -158,6 +158,41 @@ func TestNodeRole(t *testing.T) {
 	assert.False(t, f.Check(ni))
 }
 
+func TestNodePlatform(t *testing.T) {
+	setupEnv()
+	f := ConstraintFilter{}
+	task1.Spec.Placement = &api.Placement{
+		Constraints: []string{"node.platform.os == linux"},
+	}
+	require.True(t, f.SetTask(task1))
+	//node info doesn't have platform yet
+	assert.False(t, f.Check(ni))
+
+	ni.Node.Description.Platform = &api.Platform{
+		Architecture: "x86_64",
+		OS:           "linux",
+	}
+	assert.True(t, f.Check(ni))
+
+	ni.Node.Description.Platform = &api.Platform{
+		Architecture: "x86_64",
+		OS:           "windows",
+	}
+	assert.False(t, f.Check(ni))
+
+	task1.Spec.Placement = &api.Placement{
+		Constraints: []string{"node.platform.arch == amd64"},
+	}
+	require.True(t, f.SetTask(task1))
+	assert.False(t, f.Check(ni))
+
+	task1.Spec.Placement = &api.Placement{
+		Constraints: []string{"node.platform.arch != amd64"},
+	}
+	require.True(t, f.SetTask(task1))
+	assert.True(t, f.Check(ni))
+}
+
 func TestNodeLabel(t *testing.T) {
 	setupEnv()
 	f := ConstraintFilter{}