Send device list upon reconnecting to kubelet

When kubelet notifies the plugin about its restart by removing
the plugin's socket we do reconnect to kubelet, but we don't
send the current list of monitored devices to kubelet. As result
kubelet is not aware of discovered devices if it restarts.

Always send the current list of monitored devices to kubelet
upon ListAndWatch() request.

cmd/fpga_plugin/fpga_plugin.go

@@ -68,12 +68,7 @@ func (dm *deviceManager) GetDevicePluginOptions(ctx context.Context, empty *plug
 	return new(pluginapi.DevicePluginOptions), nil
 }
 
-// ListAndWatch returns a list of devices
+func (dm *deviceManager) sendDevices(stream pluginapi.DevicePlugin_ListAndWatchServer) error {
-// Whenever a device state change or a device disappears, ListAndWatch returns the new list
-func (dm *deviceManager) ListAndWatch(empty *pluginapi.Empty, stream pluginapi.DevicePlugin_ListAndWatchServer) error {
-	glog.V(2).Info("Started ListAndWatch for ", dm.fpgaID)
-
-	for dm.devices = range dm.ch {
 	resp := new(pluginapi.ListAndWatchResponse)
 	for id, device := range dm.devices {
 		resp.Devices = append(resp.Devices, &pluginapi.Device{id, device.State})
@@ -83,6 +78,23 @@ func (dm *deviceManager) ListAndWatch(empty *pluginapi.Empty, stream pluginapi.D
 		dm.srv.Stop()
 		return fmt.Errorf("device-plugin: cannot update device list: %v", err)
 	}
+
+	return nil
+}
+
+// ListAndWatch returns a list of devices
+// Whenever a device state change or a device disappears, ListAndWatch returns the new list
+func (dm *deviceManager) ListAndWatch(empty *pluginapi.Empty, stream pluginapi.DevicePlugin_ListAndWatchServer) error {
+	glog.V(2).Info("Started ListAndWatch for ", dm.fpgaID)
+
+	if err := dm.sendDevices(stream); err != nil {
+		return err
+	}
+
+	for dm.devices = range dm.ch {
+		if err := dm.sendDevices(stream); err != nil {
+			return err
+		}
 	}
 
 	return nil

cmd/fpga_plugin/fpga_plugin_test.go

@@ -30,12 +30,14 @@ import (
 // Minimal implementation of pluginapi.DevicePlugin_ListAndWatchServer
 type listAndWatchServerStub struct {
 	testDM      *deviceManager
-	generateErr bool
+	generateErr int
+	sendCounter int
 	cdata       chan []*pluginapi.Device
 }
 
 func (s *listAndWatchServerStub) Send(resp *pluginapi.ListAndWatchResponse) error {
-	if s.generateErr {
+	s.sendCounter = s.sendCounter + 1
+	if s.generateErr == s.sendCounter {
 		fmt.Println("listAndWatchServerStub::Send returns error")
 		return fmt.Errorf("Fake error")
 	}
@@ -82,11 +84,15 @@ func TestListAndWatch(t *testing.T) {
 	tcases := []struct {
 		name        string
 		updates     []map[string]deviceplugin.DeviceInfo
-		expectedErr bool
+		errorOnCall int
 	}{
 		{
 			name: "No updates and close",
 		},
+		{
+			name:        "No updates and close, but expect streaming error",
+			errorOnCall: 1,
+		},
 		{
 			name: "Send 1 update",
 			updates: []map[string]deviceplugin.DeviceInfo{
@@ -108,7 +114,7 @@ func TestListAndWatch(t *testing.T) {
 					},
 				},
 			},
-			expectedErr: true,
+			errorOnCall: 2,
 		},
 	}
 
@@ -118,8 +124,8 @@ func TestListAndWatch(t *testing.T) {
 
 		server := &listAndWatchServerStub{
 			testDM:      testDM,
-			generateErr: tt.expectedErr,
+			generateErr: tt.errorOnCall,
-			cdata:       make(chan []*pluginapi.Device, len(tt.updates)),
+			cdata:       make(chan []*pluginapi.Device, len(tt.updates)+1),
 		}
 
 		// push device infos to DM's channel
@@ -129,10 +135,10 @@ func TestListAndWatch(t *testing.T) {
 		close(devCh)
 
 		err := testDM.ListAndWatch(&pluginapi.Empty{}, server)
-		if err != nil && !tt.expectedErr {
+		if err != nil && tt.errorOnCall == 0 {
 			t.Errorf("Test case '%s': got unexpected error %v", tt.name, err)
 		}
-		if err == nil && tt.expectedErr {
+		if err == nil && tt.errorOnCall != 0 {
 			t.Errorf("Test case '%s': expected an error, but got nothing", tt.name)
 		}
 	}