Monitor-only for individual containers (#652)

* Add monitor-only label

* Add tests for monitor-only

* Treat missing monitor-only label as if the option was set to false

* Add docs for container-based monitor-only

* Add function doc

* Fix monitor-only logic

internal/actions/mocks/container.go

@@ -27,3 +27,22 @@ func CreateMockContainer(id string, name string, image string, created time.Time
 		},
 	)
 }
+
+// CreateMockContainerWithConfig creates a container substitute valid for testing
+func CreateMockContainerWithConfig(id string, name string, image string, created time.Time, config *container2.Config) container.Container {
+	content := types.ContainerJSON{
+		ContainerJSONBase: &types.ContainerJSONBase{
+			ID:      id,
+			Image:   image,
+			Name:    name,
+			Created: created.String(),
+		},
+		Config: config,
+	}
+	return *container.NewContainer(
+		&content,
+		&types.ImageInspect{
+			ID: image,
+		},
+	)
+}

internal/actions/update.go

@@ -28,7 +28,7 @@ func Update(client container.Client, params types.UpdateParams) error {
 
 	for i, targetContainer := range containers {
 		stale, err := client.IsContainerStale(targetContainer)
-		if stale && !params.NoRestart && !params.MonitorOnly && !targetContainer.HasImageInfo() {
+		if stale && !params.NoRestart && !params.MonitorOnly && !targetContainer.IsMonitorOnly() && !targetContainer.HasImageInfo() {
 			err = errors.New("no available image info")
 		}
 		if err != nil {
@@ -45,18 +45,20 @@ func Update(client container.Client, params types.UpdateParams) error {
 
 	checkDependencies(containers)
 
-	if params.MonitorOnly {
-		if params.LifecycleHooks {
-			lifecycle.ExecutePostChecks(client, params)
+	containersToUpdate := []container.Container{}
+	if !params.MonitorOnly {
+		for i := len(containers) - 1; i >= 0; i-- {
+			if !containers[i].IsMonitorOnly() {
+				containersToUpdate = append(containersToUpdate, containers[i])
+			}
 		}
-		return nil
 	}
 
 	if params.RollingRestart {
-		performRollingRestart(containers, client, params)
+		performRollingRestart(containersToUpdate, client, params)
 	} else {
-		stopContainersInReversedOrder(containers, client, params)
-		restartContainersInSortedOrder(containers, client, params)
+		stopContainersInReversedOrder(containersToUpdate, client, params)
+		restartContainersInSortedOrder(containersToUpdate, client, params)
 	}
 	if params.LifecycleHooks {
 		lifecycle.ExecutePostChecks(client, params)

internal/actions/update_test.go

@@ -5,6 +5,7 @@ import (
 	"github.com/containrrr/watchtower/pkg/container"
 	"github.com/containrrr/watchtower/pkg/container/mocks"
 	"github.com/containrrr/watchtower/pkg/types"
+	container2 "github.com/docker/docker/api/types/container"
 	cli "github.com/docker/docker/client"
 	"time"
 
@@ -80,4 +81,73 @@ var _ = Describe("the update action", func() {
 			})
 		})
 	})
+
+	When("watchtower has been instructed to monitor only", func() {
+		When("certain containers are set to monitor only", func() {
+			BeforeEach(func() {
+				client = CreateMockClient(
+					&TestData{
+						NameOfContainerToKeep: "test-container-02",
+						Containers: []container.Container{
+							CreateMockContainer(
+								"test-container-01",
+								"test-container-01",
+								"fake-image1:latest",
+								time.Now()),
+							CreateMockContainerWithConfig(
+								"test-container-02",
+								"test-container-02",
+								"fake-image2:latest",
+								time.Now(),
+								&container2.Config{
+									Labels: map[string]string{
+										"com.centurylinklabs.watchtower.monitor-only": "true",
+									},
+								}),
+						},
+					},
+					dockerClient,
+					false,
+					false,
+				)
+			})
+
+			It("should not update those containers", func() {
+				err := actions.Update(client, types.UpdateParams{Cleanup: true})
+				Expect(err).NotTo(HaveOccurred())
+				Expect(client.TestData.TriedToRemoveImageCount).To(Equal(1))
+			})
+		})
+
+		When("monitor only is set globally", func() {
+			BeforeEach(func() {
+				client = CreateMockClient(
+					&TestData{
+						Containers: []container.Container{
+							CreateMockContainer(
+								"test-container-01",
+								"test-container-01",
+								"fake-image:latest",
+								time.Now()),
+							CreateMockContainer(
+								"test-container-02",
+								"test-container-02",
+								"fake-image:latest",
+								time.Now()),
+						},
+					},
+					dockerClient,
+					false,
+					false,
+				)
+			})
+
+			It("should not update any containers", func() {
+				err := actions.Update(client, types.UpdateParams{MonitorOnly: true})
+				Expect(err).NotTo(HaveOccurred())
+				Expect(client.TestData.TriedToRemoveImageCount).To(Equal(0))
+			})
+		})
+
+	})
 })