container: add start time, process count and page fault metrics (#2566)

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Jan-Otto Kröpke <mail@jkroepke.de>

internal/headers/cri/cri_internal_test.go

@@ -23,6 +23,7 @@ import (
 	"net/http"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/stretchr/testify/require"
 	"golang.org/x/sys/windows"
@@ -69,7 +70,7 @@ func containersResponse() message {
 		message(4, message{}.string(1, "mcr.microsoft.com/windows/nanoserver")).
 		string(5, "sha256:1234").
 		varint(6, uint64(ContainerRunning)).
-		varint(7, 1700000000000000000)
+		varint(7, 1700000000123456789)
 	nanoserver = append(nanoserver, labels(8, "io.kubernetes.pod.name", "pod")...)
 	nanoserver = append(nanoserver, labels(9, "io.kubernetes.container.restartCount", "2")...)
 
@@ -100,9 +101,12 @@ func TestDecodeListContainersResponse(t *testing.T) {
 	containers, err := decodeListContainersResponse(containersResponse())
 	require.NoError(t, err)
 	require.Equal(t, []Container{
-		{ID: "abc", PodSandboxID: "sandbox-1", Name: "nanoserver", State: ContainerRunning},
+		{ID: "abc", PodSandboxID: "sandbox-1", Name: "nanoserver", State: ContainerRunning, CreatedAt: time.Unix(0, 1700000000123456789)},
 		{ID: "def", Name: "other", State: ContainerCreated},
 	}, containers)
+
+	require.Equal(t, int64(1700000000123456789), containers[0].CreatedAt.UnixNano())
+	require.True(t, containers[1].CreatedAt.IsZero())
 }
 
 func TestDecodeListPodSandboxResponse(t *testing.T) {

internal/headers/cri/types.go

@@ -18,6 +18,8 @@
 package cri
 
 import (
+	"time"
+
 	"google.golang.org/protobuf/encoding/protowire"
 )
 
@@ -54,6 +56,8 @@ type Container struct {
 	// Name is the container name from the Kubernetes pod spec.
 	Name  string
 	State ContainerState
+	// CreatedAt is the creation time of the container. It is zero if the runtime did not set it.
+	CreatedAt time.Time
 }
 
 // PodSandbox is the subset of runtime.v1.PodSandbox used by the exporter.
@@ -170,6 +174,10 @@ func decodeContainer(b []byte) (Container, error) {
 			})
 		case f.is(6, protowire.VarintType):
 			container.State = ContainerState(f.value)
+		case f.is(7, protowire.VarintType): // created_at, int64 in nanoseconds since the Unix epoch
+			if f.value != 0 {
+				container.CreatedAt = time.Unix(0, int64(f.value))
+			}
 		}
 
 		return nil