Include full queue metrics in the monitoring index (#42439)

Add queue metrics to the Metricbeat monitoring schema so they can be included in standard Agent dashboards. This is the Beats-side half of #42093. Affected metrics are: `added.{events, bytes}`, `consumed.{events, bytes}`, `removed.{events, bytes}`, and `filled.{events, bytes, pct}`, all within `monitoring.metrics.libbeat.pipeline.queue`.

Author: faec

CHANGELOG.next.asciidoc

@@ -129,6 +129,8 @@ https://github.com/elastic/beats/compare/v8.8.1\...main[Check the HEAD diff]
 - Fix setting unique registry for non beat receivers {issue}42288[42288] {pull}42292[42292]
 - The Kafka output now drops events when there is an authorisation error {issue}42343[42343] {pull}42401[42401]
 - Fix autodiscovery memory leak related to metadata of start events {pull}41748[41748]
+- All standard queue metrics are now included in metrics monitoring, including: `added.{events, bytes}`, `consumed.{events, bytes}`, `removed.{events, bytes}`, and `filled.{events, bytes, pct}`. {pull}42439[42439]
+- The following output latency metrics are now included in metrics monitoring: `output.latency.{count, max, median, p99}`. {pull}42439[42439]
 
 *Auditbeat*
 

libbeat/publisher/pipeline/monitoring.go

@@ -74,11 +74,6 @@ type metricsObserverVars struct {
 	eventsTotal, eventsFiltered, eventsPublished, eventsFailed *monitoring.Uint
 	eventsDropped, eventsRetry                                 *monitoring.Uint // (retryer) drop/retry counters
 	activeEvents                                               *monitoring.Uint
-
-	// queue metrics
-	queueACKed       *monitoring.Uint
-	queueMaxEvents   *monitoring.Uint
-	percentQueueFull *monitoring.Float
 }
 
 func newMetricsObserver(metrics *monitoring.Registry) *metricsObserver {
@@ -118,19 +113,6 @@ func newMetricsObserver(metrics *monitoring.Registry) *metricsObserver {
 			// events.dropped counts events that were dropped because errors from
 			// the output workers exceeded the configured maximum retry count.
 			eventsDropped: monitoring.NewUint(reg, "events.dropped"),
-
-			// (Gauge) queue.max_events measures the maximum number of events the
-			// queue will accept, or 0 if there is none.
-			queueMaxEvents: monitoring.NewUint(reg, "queue.max_events"),
-
-			// queue.acked counts events that have been acknowledged by the output
-			// workers. This includes events that were dropped for fatal errors,
-			// which are also reported in events.dropped.
-			queueACKed: monitoring.NewUint(reg, "queue.acked"),
-
-			// (Gauge) queue.filled.pct.events measures the fraction (from 0 to 1)
-			// of the queue's event capacity that is currently filled.
-			percentQueueFull: monitoring.NewFloat(reg, "queue.filled.pct.events"),
 		},
 	}
 }

metricbeat/module/beat/stats/data.go

@@ -71,13 +71,40 @@ var (
 				"write": c.Dict("write", s.Schema{
 					"bytes":  c.Int("bytes"),
 					"errors": c.Int("errors"),
+					"latency": c.Dict("latency", s.Schema{
+						"count":  c.Int("count"),
+						"max":    c.Int("max"),
+						"median": c.Float("median"),
+						"p99":    c.Float("p99"),
+					}),
 				}),
 			}),
 			"pipeline": c.Dict("pipeline", s.Schema{
 				"clients": c.Int("clients"),
 				"queue": c.Dict("queue", s.Schema{
-					"acked":      c.Int("acked"),
 					"max_events": c.Int("max_events"),
+
+					"added": c.Dict("added", s.Schema{
+						"events": c.Int("events"),
+						"bytes":  c.Int("bytes"),
+					}),
+					"consumed": c.Dict("consumed", s.Schema{
+						"events": c.Int("events"),
+						"bytes":  c.Int("bytes"),
+					}),
+					"removed": c.Dict("removed", s.Schema{
+						"events": c.Int("events"),
+						"bytes":  c.Int("bytes"),
+					}),
+					"filled": c.Dict("filled", s.Schema{
+						"events": c.Int("events"),
+						"bytes":  c.Int("bytes"),
+						"pct":    c.Float("pct"),
+					}),
+
+					// Backwards compatibility: "acked" is the old name for
+					// "removed.events" and should not be used by new code/dashboards.
+					"acked": c.Int("acked"),
 				}),
 				"events": c.Dict("events", s.Schema{
 					"active":    c.Int("active"),