Sort subcontainers in ContainerSpec.

Fixes google#531.

info/container.go

@@ -71,6 +71,13 @@ type ContainerReference struct {
 	Namespace string `json:"namespace,omitempty"`
 }
 
+// Sorts by container name.
+type ContainerReferenceSlice []ContainerReference
+
+func (self ContainerReferenceSlice) Len() int           { return len(self) }
+func (self ContainerReferenceSlice) Swap(i, j int)      { self[i], self[j] = self[j], self[i] }
+func (self ContainerReferenceSlice) Less(i, j int) bool { return self[i].Name < self[j].Name }
+
 // ContainerInfoQuery is used when users check a container info from the REST api.
 // It specifies how much data users want to get about a container
 type ContainerInfoRequest struct {

manager/container.go

@@ -18,6 +18,7 @@ import (
 	"flag"
 	"fmt"
 	"math"
+	"sort"
 	"sync"
 	"time"
 
@@ -319,6 +320,7 @@ func (c *containerData) updateStats() error {
 }
 
 func (c *containerData) updateSubcontainers() error {
+	var subcontainers info.ContainerReferenceSlice
 	subcontainers, err := c.handler.ListContainers(container.ListSelf)
 	if err != nil {
 		// Ignore errors if the container is dead.
@@ -327,6 +329,7 @@ func (c *containerData) updateSubcontainers() error {
 		}
 		return err
 	}
+	sort.Sort(subcontainers)
 	c.lock.Lock()
 	defer c.lock.Unlock()
 	c.info.Subcontainers = subcontainers