Fix panic on various calls when assigning Engine client to nil

Signed-off-by: Alexandre Beslic <abronan@docker.com>

Godeps/Godeps.json

@@ -104,7 +104,7 @@
 		},
 		{
 			"ImportPath": "github.com/samalba/dockerclient",
-			"Rev": "8802d66ce78e69ff16692f6fa89ad969a5711b8b"
+			"Rev": "a87700686584dc383ddb7e2bfb042e0f7a8c371b"
 		},
 		{
 			"ImportPath": "github.com/samuel/go-zookeeper/zk",

Godeps/_workspace/src/github.com/samalba/dockerclient/nopclient/nop.go

@@ -0,0 +1,147 @@
+package nopclient
+
+import (
+	"errors"
+	"io"
+
+	"github.com/samalba/dockerclient"
+)
+
+var (
+	ErrNoEngine = errors.New("Engine no longer exists")
+)
+
+type NopClient struct {
+}
+
+func NewNopClient() *NopClient {
+	return &NopClient{}
+}
+
+func (client *NopClient) Info() (*dockerclient.Info, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) ListContainers(all bool, size bool, filters string) ([]dockerclient.Container, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) InspectContainer(id string) (*dockerclient.ContainerInfo, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) InspectImage(id string) (*dockerclient.ImageInfo, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) CreateContainer(config *dockerclient.ContainerConfig, name string) (string, error) {
+	return "", ErrNoEngine
+}
+
+func (client *NopClient) ContainerLogs(id string, options *dockerclient.LogOptions) (io.ReadCloser, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) ContainerChanges(id string) ([]*dockerclient.ContainerChanges, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) StartContainer(id string, config *dockerclient.HostConfig) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) StopContainer(id string, timeout int) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) RestartContainer(id string, timeout int) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) KillContainer(id, signal string) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) Wait(id string) <-chan dockerclient.WaitResult {
+	return nil
+}
+
+func (client *NopClient) MonitorEvents(options *dockerclient.MonitorEventsOptions, stopChan <-chan struct{}) (<-chan dockerclient.EventOrError, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) StartMonitorEvents(cb dockerclient.Callback, ec chan error, args ...interface{}) {
+	return
+}
+
+func (client *NopClient) StopAllMonitorEvents() {
+	return
+}
+
+func (client *NopClient) TagImage(nameOrID string, repo string, tag string, force bool) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) StartMonitorStats(id string, cb dockerclient.StatCallback, ec chan error, args ...interface{}) {
+	return
+}
+
+func (client *NopClient) StopAllMonitorStats() {
+	return
+}
+
+func (client *NopClient) Version() (*dockerclient.Version, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) PullImage(name string, auth *dockerclient.AuthConfig) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) LoadImage(reader io.Reader) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) RemoveContainer(id string, force, volumes bool) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) ListImages(all bool) ([]*dockerclient.Image, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) RemoveImage(name string, force bool) ([]*dockerclient.ImageDelete, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) PauseContainer(name string) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) UnpauseContainer(name string) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) ExecCreate(config *dockerclient.ExecConfig) (string, error) {
+	return "", ErrNoEngine
+}
+
+func (client *NopClient) ExecStart(id string, config *dockerclient.ExecConfig) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) ExecResize(id string, width, height int) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) RenameContainer(oldName string, newName string) error {
+	return ErrNoEngine
+}
+
+func (client *NopClient) ImportImage(source string, repository string, tag string, tar io.Reader) (io.ReadCloser, error) {
+	return nil, ErrNoEngine
+}
+
+func (client *NopClient) BuildImage(image *dockerclient.BuildImage) (io.ReadCloser, error) {
+	return nil, ErrNoEngine
+}

cluster/engine.go

@@ -14,6 +14,7 @@ import (
 	log "github.com/Sirupsen/logrus"
 	"github.com/docker/docker/pkg/version"
 	"github.com/samalba/dockerclient"
+	"github.com/samalba/dockerclient/nopclient"
 )
 
 const (
@@ -31,6 +32,7 @@ const (
 func NewEngine(addr string, overcommitRatio float64) *Engine {
 	e := &Engine{
 		Addr:            addr,
+		client:          nopclient.NewNopClient(),
 		Labels:          make(map[string]string),
 		stopCh:          make(chan struct{}),
 		containers:      make(map[string]*Container),
@@ -89,18 +91,15 @@ func (e *Engine) ConnectWithClient(client dockerclient.Client) error {
 
 	// Fetch the engine labels.
 	if err := e.updateSpecs(); err != nil {
-		e.client = nil
 		return err
 	}
 
 	// Force a state update before returning.
 	if err := e.RefreshContainers(true); err != nil {
-		e.client = nil
 		return err
 	}
 
 	if err := e.RefreshImages(); err != nil {
-		e.client = nil
 		return err
 	}
 
@@ -120,16 +119,17 @@ func (e *Engine) Disconnect() {
 	e.Lock()
 	defer e.Unlock()
 
-	// do not close the chan, so it wait until the refreshLoop goroutine stops
-	e.stopCh <- struct{}{}
+	// close the chan
+	close(e.stopCh)
 	e.client.StopAllMonitorEvents()
-	e.client = nil
+	e.client = nopclient.NewNopClient()
 	e.emitEvent("engine_disconnect")
 }
 
 // isConnected returns true if the engine is connected to a remote docker API
 func (e *Engine) isConnected() bool {
-	return e.client != nil
+	_, ok := e.client.(*nopclient.NopClient)
+	return !ok
 }
 
 // IsHealthy returns true if the engine is healthy

cluster/engine_test.go

@@ -8,6 +8,7 @@ import (
 
 	"github.com/samalba/dockerclient"
 	"github.com/samalba/dockerclient/mockclient"
+	"github.com/samalba/dockerclient/nopclient"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/mock"
 )
@@ -38,8 +39,12 @@ func TestEngineConnectionFailure(t *testing.T) {
 	client := mockclient.NewMockClient()
 	client.On("Info").Return(&dockerclient.Info{}, errors.New("fail"))
 
-	// Connect() should fail and isConnected() return false.
+	// Connect() should fail
 	assert.Error(t, engine.ConnectWithClient(client))
+
+	// isConnected() should return false
+	nop := nopclient.NewNopClient()
+	assert.Error(t, engine.ConnectWithClient(nop))
 	assert.False(t, engine.isConnected())
 
 	client.Mock.AssertExpectations(t)
@@ -51,6 +56,9 @@ func TestOutdatedEngine(t *testing.T) {
 	client.On("Info").Return(&dockerclient.Info{}, nil)
 
 	assert.Error(t, engine.ConnectWithClient(client))
+
+	nop := nopclient.NewNopClient()
+	assert.Error(t, engine.ConnectWithClient(nop))
 	assert.False(t, engine.isConnected())
 
 	client.Mock.AssertExpectations(t)