feat: add no-pull label for containers (#1574)

Co-authored-by: Nedžad Alibegović <nedzad@nedzad.dev>
Co-authored-by: nils måsén <nils@piksel.se>

docs/arguments.md

@@ -234,6 +234,9 @@ Environment Variable: WATCHTOWER_NO_PULL
              Default: false
 ```
 
+Note that no-pull can also be specified on a per-container basis with the
+`com.centurylinklabs.watchtower.no-pull` label set on those containers.
+
 ## Without sending a startup message
 Do not send a message after watchtower started. Otherwise there will be an info-level notification.
 

pkg/container/client.go

@@ -280,7 +280,7 @@ func (client dockerClient) RenameContainer(c Container, newName string) error {
 func (client dockerClient) IsContainerStale(container Container) (stale bool, latestImage t.ImageID, err error) {
 	ctx := context.Background()
 
-	if !client.PullImages {
+	if !client.PullImages || container.IsNoPull() {
 		log.Debugf("Skipping image pull.")
 	} else if err := client.PullImage(ctx, container); err != nil {
 		return false, container.SafeImageID(), err

pkg/container/container.go

@@ -125,6 +125,22 @@ func (c Container) IsMonitorOnly() bool {
 	return parsedBool
 }
 
+// IsNoPull returns the value of the no-pull label. If the label is not set
+// then false is returned.
+func (c Container) IsNoPull() bool {
+	rawBool, ok := c.getLabelValue(noPullLabel)
+	if !ok {
+		return false
+	}
+
+	parsedBool, err := strconv.ParseBool(rawBool)
+	if err != nil {
+		return false
+	}
+
+	return parsedBool
+}
+
 // Scope returns the value of the scope UID label and if the label
 // was set.
 func (c Container) Scope() (string, bool) {

pkg/container/container_test.go

@@ -207,6 +207,39 @@ var _ = Describe("the container", func() {
 			})
 		})
 
+		When("checking no-pull label", func() {
+			When("no-pull label is true", func() {
+				c := MockContainer(WithLabels(map[string]string{
+					"com.centurylinklabs.watchtower.no-pull": "true",
+				}))
+				It("should return true", func() {
+					Expect(c.IsNoPull()).To(Equal(true))
+				})
+			})
+			When("no-pull label is false", func() {
+				c := MockContainer(WithLabels(map[string]string{
+					"com.centurylinklabs.watchtower.no-pull": "false",
+				}))
+				It("should return false", func() {
+					Expect(c.IsNoPull()).To(Equal(false))
+				})
+			})
+			When("no-pull label is set to an invalid value", func() {
+				c := MockContainer(WithLabels(map[string]string{
+					"com.centurylinklabs.watchtower.no-pull": "maybe",
+				}))
+				It("should return false", func() {
+					Expect(c.IsNoPull()).To(Equal(false))
+				})
+			})
+			When("no-pull label is unset", func() {
+				c = MockContainer(WithLabels(map[string]string{}))
+				It("should return false", func() {
+					Expect(c.IsNoPull()).To(Equal(false))
+				})
+			})
+		})
+
 		When("there is a pre or post update timeout", func() {
 			It("should return minute values", func() {
 				c = MockContainer(WithLabels(map[string]string{

pkg/container/metadata.go

@@ -5,6 +5,7 @@ const (
 	signalLabel            = "com.centurylinklabs.watchtower.stop-signal"
 	enableLabel            = "com.centurylinklabs.watchtower.enable"
 	monitorOnlyLabel       = "com.centurylinklabs.watchtower.monitor-only"
+	noPullLabel            = "com.centurylinklabs.watchtower.no-pull"
 	dependsOnLabel         = "com.centurylinklabs.watchtower.depends-on"
 	zodiacLabel            = "com.centurylinklabs.zodiac.original-image"
 	scope                  = "com.centurylinklabs.watchtower.scope"