Auditbeat,Metricbeat - add /inputs/ to HTTP monitoring endpoint

Make metrics published by "inputs" available through the /inputs/ route
on the HTTP monitoring endpoint of Auditbeat and Metricbeat.

For Agent, include a snapshot of those metrics within the Agent diagnostics
bundle as "input_metrics.json".

When running under Agent, each module instance is configured with only a single
metricset. That module is given a unique `id`. That ID is what will be used
as the `id` within the /inputs/ data. And that `id` will also be added as context to the
logger that is passed into every metricset so that any log messages from a metricset
can be associated back to the agent stream ID).

Relates elastic#36945

metricbeat/beater/metricbeat.go

@@ -26,6 +26,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/cfgfile"
 	"github.com/elastic/beats/v7/libbeat/common/reload"
 	"github.com/elastic/beats/v7/libbeat/management"
+	"github.com/elastic/beats/v7/libbeat/monitoring/inputmon"
 	"github.com/elastic/beats/v7/metricbeat/mb"
 	"github.com/elastic/beats/v7/metricbeat/mb/module"
 	conf "github.com/elastic/elastic-agent-libs/config"
@@ -155,6 +156,24 @@ func newMetricbeat(b *beat.Beat, c *conf.C, options ...Option) (*Metricbeat, err
 		return metricbeat, nil
 	}
 
+	if b.API != nil {
+		if err := inputmon.AttachHandler(b.API.Router()); err != nil {
+			return nil, fmt.Errorf("failed attach inputs api to monitoring endpoint server: %w", err)
+		}
+	}
+
+	if b.Manager != nil {
+		b.Manager.RegisterDiagnosticHook("input_metrics", "Metrics from active inputs.",
+			"input_metrics.json", "application/json", func() []byte {
+				data, err := inputmon.MetricSnapshotJSON()
+				if err != nil {
+					logp.L().Warnw("Failed to collect input metric snapshot for Agent diagnostics.", "error", err)
+					return []byte(err.Error())
+				}
+				return data
+			})
+	}
+
 	moduleOptions := append(
 		[]module.Option{module.WithMaxStartDelay(config.MaxStartDelay)},
 		metricbeat.moduleOptions...)

metricbeat/mb/builders.go

@@ -184,18 +184,33 @@ func newBaseMetricSets(r *Register, m Module) ([]BaseMetricSet, error) {
 			metrics := monitoring.NewRegistry()
 			monitoring.NewString(metrics, "module").Set(m.Name())
 			monitoring.NewString(metrics, "metricset").Set(name)
+			monitoring.NewString(metrics, "input").Set(m.Name() + "/" + name)
 			if host != "" {
 				monitoring.NewString(metrics, "host").Set(host)
 			}
-			monitoring.NewString(metrics, "id").Set(msID)
+			monitoring.NewString(metrics, "ephemeral_id").Set(msID)
+			if configuredID := m.Config().ID; configuredID != "" {
+				// If a module ID was configured, then use that as the ID within metrics.
+				// Note that the "ephemeral_id" is what is used as the monitoring registry
+				// key. This module ID is not unique to the MetricSet instance when multiple
+				// hosts are monitored or if multiple different MetricSet types were enabled
+				// under the same module instance.
+				monitoring.NewString(metrics, "id").Set(configuredID)
+			} else {
+				monitoring.NewString(metrics, "id").Set(msID)
+			}
 
+			logger := logp.NewLogger(m.Name() + "." + name)
+			if m.Config().ID != "" {
+				logger = logger.With("id", m.Config().ID)
+			}
 			metricsets = append(metricsets, BaseMetricSet{
 				id:      msID,
 				name:    name,
 				module:  m,
 				host:    host,
 				metrics: metrics,
-				logger:  logp.NewLogger(m.Name() + "." + name),
+				logger:  logger,
 			})
 		}
 	}

metricbeat/mb/mb.go

@@ -362,6 +362,7 @@ func (b *BaseMetricSet) Registration() MetricSetRegistration {
 // the metricset fetches not only the predefined fields but add alls raw data under
 // the raw namespace to the event.
 type ModuleConfig struct {
+	ID          string        `config:"id"` // Optional ID (not guaranteed to be unique).
 	Hosts       []string      `config:"hosts"`
 	Period      time.Duration `config:"period"     validate:"positive"`
 	Timeout     time.Duration `config:"timeout"    validate:"positive"`
@@ -375,8 +376,8 @@ type ModuleConfig struct {
 
 func (c ModuleConfig) String() string {
 	return fmt.Sprintf(`{Module:"%v", MetricSets:%v, Enabled:%v, `+
-		`Hosts:[%v hosts], Period:"%v", Timeout:"%v", Raw:%v, Query:%v}`,
-		c.Module, c.MetricSets, c.Enabled, len(c.Hosts), c.Period, c.Timeout,
+		`ID:"%s", Hosts:[%v hosts], Period:"%v", Timeout:"%v", Raw:%v, Query:%v}`,
+		c.Module, c.MetricSets, c.Enabled, c.ID, len(c.Hosts), c.Period, c.Timeout,
 		c.Raw, c.Query)
 }