kubelet: guarantee at most only one cinfo per containerID

The trailing for loop removed within this PR can include active and
inactive references. This modification will gauarantee at most only one
reference per container is returned.

Author: rphillips

pkg/kubelet/stats/cadvisor_stats_provider.go

@@ -329,17 +329,12 @@ func removeTerminatedContainerInfo(containerInfo map[string]cadvisorapiv2.Contai
 			continue
 		}
 		sort.Sort(ByCreationTime(refs))
-		i := 0
-		for ; i < len(refs); i++ {
+		for i := len(refs) - 1; i >= 0; i-- {
 			if hasMemoryAndCPUInstUsage(&refs[i].cinfo) {
-				// Stops removing when we first see an info with non-zero
-				// CPU/Memory usage.
+				result[refs[i].cgroup] = refs[i].cinfo
 				break
 			}
 		}
-		for ; i < len(refs); i++ {
-			result[refs[i].cgroup] = refs[i].cinfo
-		}
 	}
 	return result
 }

pkg/kubelet/stats/cadvisor_stats_provider_test.go

@@ -62,16 +62,10 @@ func TestRemoveTerminatedContainerInfo(t *testing.T) {
 		// The latest containers, which should be in the results.
 		"/pod0-i":  getTestContainerInfo(seedPod0Infra, pName0, namespace, leaky.PodInfraContainerName),
 		"/pod0-c0": getTestContainerInfo(seedPod0Container0, pName0, namespace, cName00),
-
-		// Duplicated containers with non-zero CPU and memory usage. This case
-		// shouldn't happen unless something goes wrong, but we want to test
-		// that the metrics reporting logic works in this scenario.
-		"/pod0-i-duplicated":  getTestContainerInfo(seedPod0Infra, pName0, namespace, leaky.PodInfraContainerName),
-		"/pod0-c0-duplicated": getTestContainerInfo(seedPod0Container0, pName0, namespace, cName00),
 	}
 	output := removeTerminatedContainerInfo(infos)
-	assert.Len(t, output, 4)
-	for _, c := range []string{"/pod0-i", "/pod0-c0", "/pod0-i-duplicated", "/pod0-c0-duplicated"} {
+	assert.Len(t, output, 2)
+	for _, c := range []string{"/pod0-i", "/pod0-c0"} {
 		if _, found := output[c]; !found {
 			t.Errorf("%q is expected to be in the output\n", c)
 		}