feat(labels): support service and container labels, update labels and cpu/memory in-place

pkg/api/resources.go

@@ -1,7 +1,11 @@
 package api
 
 import (
+	"errors"
+
 	"github.com/docker/docker/api/types/container"
+	"github.com/google/go-cmp/cmp"
+	"github.com/google/go-cmp/cmp/cmpopts"
 )
 
 const (
@@ -27,6 +31,35 @@ type ContainerResources struct {
 	Ulimits map[string]Ulimit
 }
 
+// Equals returns true if the resources are equal, treating nil and empty slices and maps as equal.
+func (r ContainerResources) Equals(other ContainerResources) bool {
+	return cmp.Equal(r, other, cmpopts.EquateEmpty())
+}
+
+// ValidateUpdateInPlace returns an error explaining why a container created with these resources can't be updated
+// to the new resources without recreating it. It returns nil if the container can be updated in place.
+// Docker can only change the CPU and memory limits of an existing container and can't remove a limit once it's set.
+func (r ContainerResources) ValidateUpdateInPlace(new ContainerResources) error {
+	// Docker treats zero values as unchanged when updating a container.
+	if r.CPU != 0 && new.CPU == 0 {
+		return errors.New("CPU limit can't be removed")
+	}
+	if r.Memory != 0 && new.Memory == 0 {
+		return errors.New("memory limit can't be removed")
+	}
+	if r.MemoryReservation != 0 && new.MemoryReservation == 0 {
+		return errors.New("memory reservation can't be removed")
+	}
+
+	r.CPU = new.CPU
+	r.Memory = new.Memory
+	r.MemoryReservation = new.MemoryReservation
+	if !r.Equals(new) {
+		return errors.New("only CPU and memory limits can be changed")
+	}
+	return nil
+}
+
 // DeviceMapping represents a device mapping between host and container.
 type DeviceMapping struct {
 	// HostPath is the path to the device on the host.