api: add PreferredAllocator interface

pkg/deviceplugin/api.go

@@ -96,6 +96,12 @@ type PostAllocator interface {
 	PostAllocate(*pluginapi.AllocateResponse) error
 }
 
+// PreferredAllocator is an optional interface implemented by device plugins.
+type PreferredAllocator interface {
+	// GetPreferredAllocation defines the list of devices preferred for allocating next.
+	GetPreferredAllocation(*pluginapi.PreferredAllocationRequest) (*pluginapi.PreferredAllocationResponse, error)
+}
+
 // ContainerPreStarter is an optional interface implemented by device plugins.
 type ContainerPreStarter interface {
 	// PreStartContainer  defines device initialization function before container is started.

pkg/deviceplugin/manager.go

@@ -22,6 +22,10 @@ import (
 	pluginapi "k8s.io/kubelet/pkg/apis/deviceplugin/v1beta1"
 )
 
+type postAllocateFunc func(*pluginapi.AllocateResponse) error
+type preStartContainerFunc func(*pluginapi.PreStartContainerRequest) error
+type getPreferredAllocationFunc func(*pluginapi.PreferredAllocationRequest) (*pluginapi.PreferredAllocationResponse, error)
+
 // updateInfo contains info for added, updated and deleted devices.
 type updateInfo struct {
 	Added   DeviceTree
@@ -73,7 +77,7 @@ type Manager struct {
 	devicePlugin Scanner
 	namespace    string
 	servers      map[string]devicePluginServer
-	createServer func(string, func(*pluginapi.AllocateResponse) error, func(*pluginapi.PreStartContainerRequest) error) devicePluginServer
+	createServer func(string, postAllocateFunc, preStartContainerFunc, getPreferredAllocationFunc) devicePluginServer
 }
 
 // NewManager creates a new instance of Manager.
@@ -107,8 +111,9 @@ func (m *Manager) Run() {
 func (m *Manager) handleUpdate(update updateInfo) {
 	klog.V(4).Info("Received dev updates:", update)
 	for devType, devices := range update.Added {
-		var postAllocate func(*pluginapi.AllocateResponse) error
-		var preStartContainer func(*pluginapi.PreStartContainerRequest) error
+		var postAllocate postAllocateFunc
+		var preStartContainer preStartContainerFunc
+		var getPreferredAllocation getPreferredAllocationFunc
 
 		if postAllocator, ok := m.devicePlugin.(PostAllocator); ok {
 			postAllocate = postAllocator.PostAllocate
@@ -118,7 +123,11 @@ func (m *Manager) handleUpdate(update updateInfo) {
 			preStartContainer = containerPreStarter.PreStartContainer
 		}
 
-		m.servers[devType] = m.createServer(devType, postAllocate, preStartContainer)
+		if preferredAllocator, ok := m.devicePlugin.(PreferredAllocator); ok {
+			getPreferredAllocation = preferredAllocator.GetPreferredAllocation
+		}
+
+		m.servers[devType] = m.createServer(devType, postAllocate, preStartContainer, getPreferredAllocation)
 		go func(dt string) {
 			err := m.servers[dt].Serve(m.namespace)
 			if err != nil {

pkg/deviceplugin/manager_test.go

@@ -265,7 +265,7 @@ func TestHandleUpdate(t *testing.T) {
 		mgr := Manager{
 			devicePlugin: &devicePluginStub{},
 			servers:      tt.servers,
-			createServer: func(string, func(*pluginapi.AllocateResponse) error, func(*pluginapi.PreStartContainerRequest) error) devicePluginServer {
+			createServer: func(string, postAllocateFunc, preStartContainerFunc, getPreferredAllocationFunc) devicePluginServer {
 				return &serverStub{}
 			},
 		}
@@ -279,7 +279,7 @@ func TestHandleUpdate(t *testing.T) {
 
 func TestRun(t *testing.T) {
 	mgr := NewManager("testnamespace", &devicePluginStub{})
-	mgr.createServer = func(string, func(*pluginapi.AllocateResponse) error, func(*pluginapi.PreStartContainerRequest) error) devicePluginServer {
+	mgr.createServer = func(string, postAllocateFunc, preStartContainerFunc, getPreferredAllocationFunc) devicePluginServer {
 		return &serverStub{}
 	}
 	mgr.Run()

pkg/deviceplugin/server.go

@@ -51,27 +51,30 @@ type devicePluginServer interface {
 
 // server implements devicePluginServer and pluginapi.PluginInterfaceServer interfaces.
 type server struct {
-	devType           string
-	grpcServer        *grpc.Server
-	updatesCh         chan map[string]DeviceInfo
-	devices           map[string]DeviceInfo
-	postAllocate      func(*pluginapi.AllocateResponse) error
-	preStartContainer func(*pluginapi.PreStartContainerRequest) error
-	state             serverState
-	stateMutex        sync.Mutex
+	devType                string
+	grpcServer             *grpc.Server
+	updatesCh              chan map[string]DeviceInfo
+	devices                map[string]DeviceInfo
+	postAllocate           postAllocateFunc
+	preStartContainer      preStartContainerFunc
+	getPreferredAllocation getPreferredAllocationFunc
+	state                  serverState
+	stateMutex             sync.Mutex
 }
 
 // newServer creates a new server satisfying the devicePluginServer interface.
 func newServer(devType string,
-	postAllocate func(*pluginapi.AllocateResponse) error,
-	preStartContainer func(*pluginapi.PreStartContainerRequest) error) devicePluginServer {
+	postAllocate postAllocateFunc,
+	preStartContainer preStartContainerFunc,
+	getPreferredAllocation getPreferredAllocationFunc) devicePluginServer {
 	return &server{
-		devType:           devType,
-		updatesCh:         make(chan map[string]DeviceInfo, 1), // TODO: is 1 needed?
-		devices:           make(map[string]DeviceInfo),
-		postAllocate:      postAllocate,
-		preStartContainer: preStartContainer,
-		state:             uninitialized,
+		devType:                devType,
+		updatesCh:              make(chan map[string]DeviceInfo, 1), // TODO: is 1 needed?
+		devices:                make(map[string]DeviceInfo),
+		postAllocate:           postAllocate,
+		preStartContainer:      preStartContainer,
+		getPreferredAllocation: getPreferredAllocation,
+		state:                  uninitialized,
 	}
 }
 
@@ -162,6 +165,9 @@ func (srv *server) PreStartContainer(ctx context.Context, rqt *pluginapi.PreStar
 }
 
 func (srv *server) GetPreferredAllocation(ctx context.Context, rqt *pluginapi.PreferredAllocationRequest) (*pluginapi.PreferredAllocationResponse, error) {
+	if srv.getPreferredAllocation != nil {
+		return srv.getPreferredAllocation(rqt)
+	}
 	return nil, errors.New("GetPreferredAllocation should not be called as this device plugin doesn't implement it")
 }
 

pkg/deviceplugin/server_test.go

@@ -530,7 +530,7 @@ func TestGetPreferredAllocation(t *testing.T) {
 }
 
 func TestNewServer(t *testing.T) {
-	_ = newServer("test", nil, nil)
+	_ = newServer("test", nil, nil, nil)
 }
 
 func TestUpdate(t *testing.T) {