[receiver/kubeletstats] Add uptime metric for nodes, pods, and contai…

…ners (#25867)

**Description:**
Adds a new monotonic, cumulative sum metric for tracking uptime of
nodes, pods, and containers. Uptime is calculated as the number of
seconds since the object's `StartTime`.

**Testing:** 
Updated unit tests.  Tested locally using the otel demo

.chloggen/kubeletstats-uptime.yaml

@@ -0,0 +1,27 @@
+# Use this changelog template to create an entry for release notes.
+
+# One of 'breaking', 'deprecation', 'new_component', 'enhancement', 'bug_fix'
+change_type: enhancement
+
+# The name of the component, or a single word describing the area of concern, (e.g. filelogreceiver)
+component: kubeletstatsreceiver
+
+# A brief description of the change.  Surround your text with quotes ("") if it needs to start with a backtick (`).
+note: Add a new `uptime` metric for nodes, pods, and containers to track how many seconds have passed since the object started
+
+# Mandatory: One or more tracking issues related to the change. You can use the PR number here if no issue exists.
+issues: [25867]
+
+# (Optional) One or more lines of additional information to render under the primary note.
+# These lines will be padded with 2 spaces and then inserted directly into the document.
+# Use pipe (|) for multiline entries.
+subtext:
+
+# If your change doesn't affect end users or the exported elements of any package,
+# you should instead start your pull request title with [chore] or use the "Skip Changelog" label.
+# Optional: The change log or logs in which this entry should be included.
+# e.g. '[user]' or '[user, api]'
+# Include 'user' if the change is relevant to end users.
+# Include 'api' if there is a change to a library API.
+# Default: '[user]'
+change_logs: []

receiver/kubeletstatsreceiver/documentation.md

@@ -376,6 +376,40 @@ The inodes used by the filesystem. This may not equal inodes - free because file
 | ---- | ----------- | ---------- |
 | 1 | Gauge | Int |
 
+## Optional Metrics
+
+The following metrics are not emitted by default. Each of them can be enabled by applying the following configuration:
+
+```yaml
+metrics:
+  <metric_name>:
+    enabled: true
+```
+
+### container.uptime
+
+The time since the container started
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| s | Sum | Int | Cumulative | true |
+
+### k8s.node.uptime
+
+The time since the node started
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| s | Sum | Int | Cumulative | true |
+
+### k8s.pod.uptime
+
+The time since the pod started
+
+| Unit | Metric Type | Value Type | Aggregation Temporality | Monotonic |
+| ---- | ----------- | ---------- | ----------------------- | --------- |
+| s | Sum | Int | Cumulative | true |
+
 ## Resource Attributes
 
 | Name | Description | Values | Enabled |

receiver/kubeletstatsreceiver/internal/kubelet/accumulator.go

@@ -9,6 +9,7 @@ import (
 	"go.opentelemetry.io/collector/pdata/pcommon"
 	"go.opentelemetry.io/collector/pdata/pmetric"
 	"go.uber.org/zap"
+	v1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	stats "k8s.io/kubelet/pkg/apis/stats/v1alpha1"
 
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/kubeletstatsreceiver/internal/metadata"
@@ -41,12 +42,20 @@ type metricDataAccumulator struct {
 	mbs                   *metadata.MetricsBuilders
 }
 
+func addUptimeMetric(mb *metadata.MetricsBuilder, uptimeMetric metadata.RecordIntDataPointFunc, startTime v1.Time, currentTime pcommon.Timestamp) {
+	if !startTime.IsZero() {
+		value := int64(time.Since(startTime.Time).Seconds())
+		uptimeMetric(mb, currentTime, value)
+	}
+}
+
 func (a *metricDataAccumulator) nodeStats(s stats.NodeStats) {
 	if !a.metricGroupsToCollect[NodeMetricGroup] {
 		return
 	}
 
 	currentTime := pcommon.NewTimestampFromTime(a.time)
+	addUptimeMetric(a.mbs.NodeMetricsBuilder, metadata.NodeUptimeMetrics.Uptime, s.StartTime, currentTime)
 	addCPUMetrics(a.mbs.NodeMetricsBuilder, metadata.NodeCPUMetrics, s.CPU, currentTime)
 	addMemoryMetrics(a.mbs.NodeMetricsBuilder, metadata.NodeMemoryMetrics, s.Memory, currentTime)
 	addFilesystemMetrics(a.mbs.NodeMetricsBuilder, metadata.NodeFilesystemMetrics, s.Fs, currentTime)
@@ -66,6 +75,7 @@ func (a *metricDataAccumulator) podStats(s stats.PodStats) {
 	}
 
 	currentTime := pcommon.NewTimestampFromTime(a.time)
+	addUptimeMetric(a.mbs.PodMetricsBuilder, metadata.PodUptimeMetrics.Uptime, s.StartTime, currentTime)
 	addCPUMetrics(a.mbs.PodMetricsBuilder, metadata.PodCPUMetrics, s.CPU, currentTime)
 	addMemoryMetrics(a.mbs.PodMetricsBuilder, metadata.PodMemoryMetrics, s.Memory, currentTime)
 	addFilesystemMetrics(a.mbs.PodMetricsBuilder, metadata.PodFilesystemMetrics, s.EphemeralStorage, currentTime)
@@ -98,6 +108,7 @@ func (a *metricDataAccumulator) containerStats(sPod stats.PodStats, s stats.Cont
 	}
 
 	currentTime := pcommon.NewTimestampFromTime(a.time)
+	addUptimeMetric(a.mbs.ContainerMetricsBuilder, metadata.ContainerUptimeMetrics.Uptime, s.StartTime, currentTime)
 	addCPUMetrics(a.mbs.ContainerMetricsBuilder, metadata.ContainerCPUMetrics, s.CPU, currentTime)
 	addMemoryMetrics(a.mbs.ContainerMetricsBuilder, metadata.ContainerMemoryMetrics, s.Memory, currentTime)
 	addFilesystemMetrics(a.mbs.ContainerMetricsBuilder, metadata.ContainerFilesystemMetrics, s.Rootfs, currentTime)

receiver/kubeletstatsreceiver/internal/kubelet/metrics_test.go

@@ -105,7 +105,7 @@ func requireResourceOk(t *testing.T, resource pcommon.Resource) {
 }
 
 func TestWorkingSetMem(t *testing.T) {
-	metrics := indexedFakeMetrics()
+	metrics := indexedFakeMetrics(fakeMetrics())
 	requireContains(t, metrics, "k8s.pod.memory.working_set")
 	requireContains(t, metrics, "container.memory.working_set")
 
@@ -115,7 +115,7 @@ func TestWorkingSetMem(t *testing.T) {
 }
 
 func TestPageFaults(t *testing.T) {
-	metrics := indexedFakeMetrics()
+	metrics := indexedFakeMetrics(fakeMetrics())
 	requireContains(t, metrics, "k8s.pod.memory.page_faults")
 	requireContains(t, metrics, "container.memory.page_faults")
 
@@ -125,7 +125,7 @@ func TestPageFaults(t *testing.T) {
 }
 
 func TestMajorPageFaults(t *testing.T) {
-	metrics := indexedFakeMetrics()
+	metrics := indexedFakeMetrics(fakeMetrics())
 	requireContains(t, metrics, "k8s.pod.memory.major_page_faults")
 	requireContains(t, metrics, "container.memory.major_page_faults")
 
@@ -134,8 +134,36 @@ func TestMajorPageFaults(t *testing.T) {
 	require.Equal(t, int64(12), value)
 }
 
+func TestUptime(t *testing.T) {
+	rc := &fakeRestClient{}
+	statsProvider := NewStatsProvider(rc)
+	summary, _ := statsProvider.StatsSummary()
+	mgs := map[MetricGroup]bool{
+		ContainerMetricGroup: true,
+		PodMetricGroup:       true,
+		NodeMetricGroup:      true,
+	}
+
+	cfg := metadata.DefaultMetricsBuilderConfig()
+	cfg.Metrics.K8sNodeUptime.Enabled = true
+	cfg.Metrics.K8sPodUptime.Enabled = true
+	cfg.Metrics.ContainerUptime.Enabled = true
+
+	mbs := &metadata.MetricsBuilders{
+		NodeMetricsBuilder:      metadata.NewMetricsBuilder(cfg, receivertest.NewNopCreateSettings()),
+		PodMetricsBuilder:       metadata.NewMetricsBuilder(cfg, receivertest.NewNopCreateSettings()),
+		ContainerMetricsBuilder: metadata.NewMetricsBuilder(cfg, receivertest.NewNopCreateSettings()),
+	}
+
+	metrics := indexedFakeMetrics(MetricsData(zap.NewNop(), summary, Metadata{}, mgs, mbs))
+
+	requireContains(t, metrics, "k8s.node.uptime")
+	requireContains(t, metrics, "k8s.pod.uptime")
+	requireContains(t, metrics, "container.uptime")
+}
+
 func TestEmitMetrics(t *testing.T) {
-	metrics := indexedFakeMetrics()
+	metrics := indexedFakeMetrics(fakeMetrics())
 	metricNames := []string{
 		"k8s.node.network.io",
 		"k8s.node.network.errors",
@@ -158,8 +186,7 @@ func requireContains(t *testing.T, metrics map[string][]pmetric.Metric, metricNa
 	require.True(t, found)
 }
 
-func indexedFakeMetrics() map[string][]pmetric.Metric {
-	mds := fakeMetrics()
+func indexedFakeMetrics(mds []pmetric.Metrics) map[string][]pmetric.Metric {
 	metrics := make(map[string][]pmetric.Metric)
 	for _, md := range mds {
 		for i := 0; i < md.ResourceMetrics().Len(); i++ {