Export cortex_attributed_series_overflow_labels (#12846)

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#### What this PR does

Exports a new constant metric `cortex_attributed_series_overflow_labels
` with the configured cost-attribution labels set to overflow values.

#### Which issue(s) this PR fixes or relates to

Fixes needs in the billing pipeline.

#### Checklist

- [x] Tests updated.
- [ ] Documentation added.
- [x] `CHANGELOG.md` updated - the order of entries should be
`[CHANGE]`, `[FEATURE]`, `[ENHANCEMENT]`, `[BUGFIX]`. If changelog entry
is not needed, please add the `changelog-not-needed` label to the PR.
- [ ]
[`about-versioning.md`](https://github.com/grafana/mimir/blob/main/docs/sources/mimir/configure/about-versioning.md)
updated with experimental features.

---------

Signed-off-by: Oleg Zaytsev <[email protected]>

Author: colega

CHANGELOG.md

@@ -66,6 +66,7 @@
 * [ENHANCEMENT] Compactor: Log sizes of downloaded and uploaded blocks. #12656
 * [ENHANCEMENT] Ingester: Add `cortex_ingest_storage_reader_receive_and_consume_delay_seconds` metric tracking the time between when a write request is received in the distributor and its content is ingested in ingesters, when the ingest storage is enabled. #12751
 * [ENHANCEMENT] Ruler: Add `ruler_evaluation_consistency_max_delay` per-tenant configuration option support, to specify the maximum tolerated ingestion delay for eventually consistent rule evaluations. This feature is used only when ingest storage is enabled. By default, no maximum delay is enforced. #12751
+* [ENHANCEMENT] Ingester: Export `cortex_attributed_series_overflow_labels` metric on the `/usage-metrics` metrics endpoint with the configured cost-attribution labels set to overflow value. #12846
 * [BUGFIX] Distributor: Calculate `WriteResponseStats` before validation and `PushWrappers`. This prevents clients using Remote-Write 2.0 from seeing a diff in written samples, histograms and exemplars. #12682
 * [BUGFIX] Compactor: Fix cortex_compactor_block_uploads_failed_total metric showing type="unknown". #12477
 * [BUGFIX] Querier: Samples with the same timestamp are merged deterministically. Previously, this could lead to flapping query results when an out-of-order sample is ingested that conflicts with a previously ingested in-order sample's value. #8673

pkg/costattribution/active_tracker.go

@@ -29,6 +29,7 @@ type counters struct {
 type ActiveSeriesTracker struct {
 	userID                                         string
 	activeSeriesPerUserAttribution                 *prometheus.Desc
+	attributedOverflowLabels                       *prometheus.Desc
 	activeNativeHistogramSeriesPerUserAttribution  *prometheus.Desc
 	activeNativeHistogramBucketsPerUserAttribution *prometheus.Desc
 	logger                                         log.Logger
@@ -77,6 +78,9 @@ func NewActiveSeriesTracker(userID string, trackedLabels []costattributionmodel.
 	ast.activeSeriesPerUserAttribution = prometheus.NewDesc("cortex_ingester_attributed_active_series",
 		"The total number of active series per user and attribution.", variableLabels[:len(variableLabels)-1],
 		prometheus.Labels{trackerLabel: defaultTrackerName})
+	ast.attributedOverflowLabels = prometheus.NewDesc("cortex_attributed_series_overflow_labels",
+		"The overflow labels for this tenant. This metric is always 1 for tenants with active series, it is only used to have the overflow labels available in the recording rules without knowing their names.", variableLabels[:len(variableLabels)-1],
+		prometheus.Labels{trackerLabel: defaultTrackerName})
 	ast.activeNativeHistogramSeriesPerUserAttribution = prometheus.NewDesc("cortex_ingester_attributed_active_native_histogram_series",
 		"The total number of active native histogram series per user and attribution.", variableLabels[:len(variableLabels)-1],
 		prometheus.Labels{trackerLabel: defaultTrackerName})
@@ -213,6 +217,8 @@ func (at *ActiveSeriesTracker) Decrement(lbls labels.Labels, nativeHistogramBuck
 }
 
 func (at *ActiveSeriesTracker) Collect(out chan<- prometheus.Metric) {
+	out <- prometheus.MustNewConstMetric(at.attributedOverflowLabels, prometheus.GaugeValue, 1, at.overflowLabels[:len(at.overflowLabels)-1]...)
+
 	at.observedMtx.RLock()
 	if !at.overflowSince.IsZero() {
 		var activeSeries int64

pkg/costattribution/manager_test.go

@@ -80,6 +80,10 @@ func TestManager_CreateDeleteTracker(t *testing.T) {
 		# HELP cortex_ingester_attributed_active_series The total number of active series per user and attribution.
         # TYPE cortex_ingester_attributed_active_series gauge
         cortex_ingester_attributed_active_series{team="bar",tenant="user1",tracker="cost-attribution"} 3
+		# HELP cortex_attributed_series_overflow_labels The overflow labels for this tenant. This metric is always 1 for tenants with active series, it is only used to have the overflow labels available in the recording rules without knowing their names.
+		# TYPE cortex_attributed_series_overflow_labels gauge
+		cortex_attributed_series_overflow_labels{team="__overflow__",tenant="user1",tracker="cost-attribution"} 1
+		cortex_attributed_series_overflow_labels{department="__overflow__",service="__overflow__",tenant="user3",tracker="cost-attribution"} 1
 		`
 		assert.NoError(t, testutil.GatherAndCompare(costAttributionReg,
 			strings.NewReader(expectedMetrics),
@@ -88,6 +92,7 @@ func TestManager_CreateDeleteTracker(t *testing.T) {
 			"cortex_ingester_attributed_active_series",
 			"cortex_ingester_attributed_active_native_histogram_series",
 			"cortex_ingester_attributed_active_native_histogram_buckets",
+			"cortex_attributed_series_overflow_labels",
 		))
 
 		manager.ActiveSeriesTracker("user1").Decrement(labels.FromStrings("team", "bar"), 50)