implemented enableLabel by a Filter

README.md

@@ -129,9 +129,9 @@ docker run -d --label=com.centurylinklabs.watchtower.stop-signal=SIGHUP someimag
 
 ## Selectively Watching Containers
 
-By default, watchtower will watch all containers.
+By default, watchtower will watch all containers. However, sometimes only some containers should be updated.
-However, sometimes only some containers should be updated.
+
-If you need to selectively watch containers, pass the --label-enable flag on startup and set the *com.centurylinklabs.watchtower.enable* label with a value of true for the containers you want to watch.
+If you need to only include only some containers, pass the --label-enable flag on startup and set the *com.centurylinklabs.watchtower.enable* label with a value of true for the containers you want to watch.
 
 ```docker
 LABEL com.centurylinklabs.watchtower.enable="true"

actions/check.go

@@ -6,14 +6,12 @@ import (
 	"github.com/v2tec/watchtower/container"
 )
 
-func watchtowerContainersFilter(c container.Container) bool { return c.IsWatchtower() }
-
 // CheckPrereqs will ensure that there are not multiple instances of the
 // watchtower running simultaneously. If multiple watchtower containers are
 // detected, this function will stop and remove all but the most recently
 // started container.
 func CheckPrereqs(client container.Client, cleanup bool) error {
-	containers, err := client.ListContainers(watchtowerContainersFilter)
+	containers, err := client.ListContainers(container.WatchtowerContainersFilter)
 	if err != nil {
 		return err
 	}

actions/update.go

@@ -12,31 +12,14 @@ var (
 	letters  = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ")
 )
 
-func allContainersFilter(container.Container) bool { return true }
-
-func containerFilter(names []string) container.Filter {
-	if len(names) == 0 {
-		return allContainersFilter
-	}
-
-	return func(c container.Container) bool {
-		for _, name := range names {
-			if (name == c.Name()) || (name == c.Name()[1:]) {
-				return true
-			}
-		}
-		return false
-	}
-}
-
 // Update looks at the running Docker containers to see if any of the images
 // used to start those containers have been updated. If a change is detected in
 // any of the images, the associated containers are stopped and restarted with
 // the new image.
-func Update(client container.Client, names []string, cleanup bool, noRestart bool, timeout time.Duration) error {
+func Update(client container.Client, filter container.Filter, cleanup bool, noRestart bool, timeout time.Duration) error {
 	log.Debug("Checking containers for updated images")
 
-	containers, err := client.ListContainers(containerFilter(names))
+	containers, err := client.ListContainers(filter)
 	if err != nil {
 		return err
 	}

container/client.go

@@ -5,10 +5,10 @@ import (
 	"io/ioutil"
 	"time"
 
-	log "github.com/sirupsen/logrus"
 	"github.com/docker/docker/api/types"
 	"github.com/docker/docker/api/types/network"
 	dockerclient "github.com/docker/docker/client"
+	log "github.com/sirupsen/logrus"
 	"golang.org/x/net/context"
 )
 
@@ -16,10 +16,6 @@ const (
 	defaultStopSignal = "SIGTERM"
 )
 
-// A Filter is a prototype for a function that can be used to filter the
-// results from a call to the ListContainers() method on the Client.
-type Filter func(Container) bool
-
 // A Client is the interface through which watchtower interacts with the
 // Docker API.
 type Client interface {
@@ -37,20 +33,19 @@ type Client interface {
 //  * DOCKER_HOST			the docker-engine host to send api requests to
 //  * DOCKER_TLS_VERIFY		whether to verify tls certificates
 //  * DOCKER_API_VERSION	the minimum docker api version to work with
-func NewClient(pullImages, enableLabel bool) Client {
+func NewClient(pullImages bool) Client {
 	cli, err := dockerclient.NewEnvClient()
 
 	if err != nil {
 		log.Fatalf("Error instantiating Docker client: %s", err)
 	}
 
-	return dockerClient{api: cli, pullImages: pullImages, enableLabel: enableLabel}
+	return dockerClient{api: cli, pullImages: pullImages}
 }
 
 type dockerClient struct {
-	api         *dockerclient.Client
+	api        *dockerclient.Client
-	pullImages  bool
+	pullImages bool
-	enableLabel bool
 }
 
 func (client dockerClient) ListContainers(fn Filter) ([]Container, error) {
@@ -62,6 +57,7 @@ func (client dockerClient) ListContainers(fn Filter) ([]Container, error) {
 	runningContainers, err := client.api.ContainerList(
 		bg,
 		types.ContainerListOptions{})
+
 	if err != nil {
 		return nil, err
 	}
@@ -79,15 +75,6 @@ func (client dockerClient) ListContainers(fn Filter) ([]Container, error) {
 
 		c := Container{containerInfo: &containerInfo, imageInfo: &imageInfo}
 
-		if client.enableLabel {
-			// If label filtering is enabled, containers should only be enabled
-			// if the label is specifically set to true.
-			enabledLabel, ok := c.Enabled()
-			if !ok || !enabledLabel {
-				continue
-			}
-		}
-
 		if fn(c) {
 			cs = append(cs, c)
 		}

container/filters.go

@@ -0,0 +1,61 @@
+package container
+
+// A Filter is a prototype for a function that can be used to filter the
+// results from a call to the ListContainers() method on the Client.
+type Filter func(FilterableContainer) bool
+
+// A FilterableContainer is the interface which is used to filter
+// containers.
+type FilterableContainer interface {
+	Name() string
+	IsWatchtower() bool
+	Enabled() (bool, bool)
+}
+
+// WatchtowerContainersFilter filters only watchtower containers
+func WatchtowerContainersFilter(c FilterableContainer) bool { return c.IsWatchtower() }
+
+// Filter no containers and returns all
+func noFilter(FilterableContainer) bool { return true }
+
+// Filters containers which don't have a specified name
+func filterByNames(names []string, baseFilter Filter) Filter {
+	if len(names) == 0 {
+		return baseFilter
+	}
+
+	return func(c FilterableContainer) bool {
+		for _, name := range names {
+			if (name == c.Name()) || (name == c.Name()[1:]) {
+				return baseFilter(c)
+			}
+		}
+		return false
+	}
+}
+
+// Filters out containers that don't have the 'enableLabel'
+func filterByEnableLabel(baseFilter Filter) Filter {
+	return func(c FilterableContainer) bool {
+		// If label filtering is enabled, containers should only be enabled
+		// if the label is specifically set to true.
+		enabledLabel, ok := c.Enabled()
+		if !ok || !enabledLabel {
+			return false
+		}
+
+		return baseFilter(c)
+	}
+}
+
+// BuildFilter creates the needed filter of containers
+func BuildFilter(names []string, enableLabel bool) Filter {
+	filter := noFilter
+	filter = filterByNames(names, filter)
+	if enableLabel {
+		// If label filtering is enabled, containers should only be considered
+		// if the label is specifically set.
+		filter = filterByEnableLabel(filter)
+	}
+	return filter
+}

main.go

@@ -29,6 +29,7 @@ var (
 	scheduleSpec string
 	cleanup      bool
 	noRestart    bool
+	enableLabel  bool
 	notifier     *notifications.Notifier
 	timeout		 time.Duration
 )
@@ -189,6 +190,7 @@ func before(c *cli.Context) error {
 	if timeout < 0 {
 		log.Fatal("Please specify a positive value for timeout value.")
 	}
+	enableLabel = c.GlobalBool("label-enable")
 
 	// configure environment vars for client
 	err := envConfig(c)
@@ -196,7 +198,7 @@ func before(c *cli.Context) error {
 		return err
 	}
 
-	client = container.NewClient(!c.GlobalBool("no-pull"), c.GlobalBool("label-enable"))
+	client = container.NewClient(!c.GlobalBool("no-pull"))
 	notifier = notifications.NewNotifier(c)
 
 	return nil
@@ -209,6 +211,8 @@ func start(c *cli.Context) error {
 		log.Fatal(err)
 	}
 
+	filter := container.BuildFilter(names, enableLabel)
+
 	tryLockSem := make(chan bool, 1)
 	tryLockSem <- true
 
@@ -220,7 +224,7 @@ func start(c *cli.Context) error {
 			case v := <-tryLockSem:
 				defer func() { tryLockSem <- v }()
 				notifier.StartNotification()
-				if err := actions.Update(client, names, cleanup, noRestart, timeout); err != nil {
+				if err := actions.Update(client, filter, cleanup, noRestart, timeout); err != nil {
 					log.Println(err)
 				}
 				notifier.SendNotification()