service ps: Truncate Task IDs

- Refactored to move resolution code into the idresolver
- Made `ps` output more bearable by shortening service IDs in task names

Signed-off-by: Andrea Luzzardi <aluzzardi@gmail.com>

command/idresolver/idresolver.go

@@ -7,6 +7,7 @@ import (
 
 	"github.com/docker/docker/api/types/swarm"
 	"github.com/docker/docker/client"
+	"github.com/docker/docker/pkg/stringid"
 )
 
 // IDResolver provides ID to Name resolution.
@@ -26,7 +27,7 @@ func New(client client.APIClient, noResolve bool) *IDResolver {
 }
 
 func (r *IDResolver) get(ctx context.Context, t interface{}, id string) (string, error) {
-	switch t.(type) {
+	switch t := t.(type) {
 	case swarm.Node:
 		node, _, err := r.client.NodeInspectWithRaw(ctx, id)
 		if err != nil {
@@ -45,6 +46,25 @@ func (r *IDResolver) get(ctx context.Context, t interface{}, id string) (string,
 			return id, nil
 		}
 		return service.Spec.Annotations.Name, nil
+	case swarm.Task:
+		// If the caller passes the full task there's no need to do a lookup.
+		if t.ID == "" {
+			var err error
+
+			t, _, err = r.client.TaskInspectWithRaw(ctx, id)
+			if err != nil {
+				return id, nil
+			}
+		}
+		taskID := stringid.TruncateID(t.ID)
+		if t.ServiceID == "" {
+			return taskID, nil
+		}
+		service, err := r.Resolve(ctx, swarm.Service{}, t.ServiceID)
+		if err != nil {
+			return "", err
+		}
+		return fmt.Sprintf("%s.%d.%s", service, t.Slot, taskID), nil
 	default:
 		return "", fmt.Errorf("unsupported type")
 	}

command/task/print.go

@@ -74,38 +74,24 @@ func PrintQuiet(dockerCli *command.DockerCli, tasks []swarm.Task) error {
 }
 
 func print(out io.Writer, ctx context.Context, tasks []swarm.Task, resolver *idresolver.IDResolver, noTrunc bool) error {
-	prevServiceName := ""
+	prevService := ""
 	prevSlot := 0
 	for _, task := range tasks {
-		serviceName, err := resolver.Resolve(ctx, swarm.Service{}, task.ServiceID)
-		if err != nil {
-			return err
-		}
+		name, err := resolver.Resolve(ctx, task, task.ID)
+
 		nodeValue, err := resolver.Resolve(ctx, swarm.Node{}, task.NodeID)
 		if err != nil {
 			return err
 		}
 
-		name := task.Annotations.Name
-		// TODO: This is the fallback <ServiceName>.<Slot>.<taskID> in case task name is not present in
-		// Annotations (upgraded from 1.12).
-		// We may be able to remove the following in the future.
-		if name == "" {
-			if task.Slot != 0 {
-				name = fmt.Sprintf("%v.%v.%v", serviceName, task.Slot, task.ID)
-			} else {
-				name = fmt.Sprintf("%v.%v.%v", serviceName, task.NodeID, task.ID)
-			}
-		}
-
 		// Indent the name if necessary
 		indentedName := name
 		// Since the new format of the task name is <ServiceName>.<Slot>.<taskID>, we should only compare
 		// <ServiceName> and <Slot> here.
-		if prevServiceName == serviceName && prevSlot == task.Slot {
+		if prevService == task.ServiceID && prevSlot == task.Slot {
 			indentedName = fmt.Sprintf(" \\_ %s", indentedName)
 		}
-		prevServiceName = serviceName
+		prevService = task.ServiceID
 		prevSlot = task.Slot
 
 		// Trim and quote the error message.