feat(exporter): add Flow component for agent Integration (#5072)

* feat(exporter): add Flow component for agent's integration

* doc(changelog): add new Feature entry

* chore(comp/agent): correct comp name in comments

* Update prometheus.exporter.agent.md

Co-authored-by: Clayton Cornell <[email protected]>

* feat(comp/agent): allow defining multiple blocks of agent's Prom exporter

---------

Co-authored-by: Clayton Cornell <[email protected]>

CHANGELOG.md

@@ -44,6 +44,7 @@ Main (unreleased)
   - `otelcol.processor.probabilistic_sampler` samples logs and traces based on configuration options. (@mar4uk)
   - `remote.kubernetes.configmap` loads a configmap's data for use in other components (@captncraig)
   - `remote.kubernetes.secret` loads a secret's data for use in other components (@captncraig)
+  - `prometheus.exporter.agent` - scrape agent's metrics. (@hainenber)
 
 - Flow: allow the HTTP server to be configured with TLS in the config file
   using the new `http` config block. (@rfratto)

component/all/all.go

@@ -87,6 +87,7 @@ import (
 	_ "github.com/grafana/agent/component/otelcol/receiver/otlp"                    // Import otelcol.receiver.otlp
 	_ "github.com/grafana/agent/component/otelcol/receiver/prometheus"              // Import otelcol.receiver.prometheus
 	_ "github.com/grafana/agent/component/otelcol/receiver/zipkin"                  // Import otelcol.receiver.zipkin
+	_ "github.com/grafana/agent/component/prometheus/exporter/agent"                // Import prometheus.exporter.agent
 	_ "github.com/grafana/agent/component/prometheus/exporter/apache"               // Import prometheus.exporter.apache
 	_ "github.com/grafana/agent/component/prometheus/exporter/azure"                // Import prometheus.exporter.azure
 	_ "github.com/grafana/agent/component/prometheus/exporter/blackbox"             // Import prometheus.exporter.blackbox

component/prometheus/exporter/agent/agent.go

@@ -0,0 +1,41 @@
+package agent
+
+import (
+	"github.com/grafana/agent/component"
+	"github.com/grafana/agent/component/prometheus/exporter"
+	"github.com/grafana/agent/pkg/integrations"
+	"github.com/grafana/agent/pkg/integrations/agent"
+)
+
+func init() {
+	component.Register(component.Registration{
+		Name:          "prometheus.exporter.agent",
+		Args:          Arguments{},
+		Exports:       exporter.Exports{},
+		NeedsServices: exporter.RequiredServices(),
+		Build:         exporter.New(createExporter, "agent"),
+	})
+}
+
+func createExporter(opts component.Options, args component.Arguments) (integrations.Integration, error) {
+	a := args.(Arguments)
+	return a.Convert().NewIntegration(opts.Logger)
+}
+
+// Arguments holds values which are used to configured the prometheus.exporter.agent component.
+type Arguments struct{}
+
+// Exports holds the values exported by the prometheus.exporter.agent component.
+type Exports struct{}
+
+// DefaultArguments defines the default settings
+var DefaultArguments = Arguments{}
+
+// SetToDefault implements river.Defaulter
+func (args *Arguments) SetToDefault() {
+	*args = DefaultArguments
+}
+
+func (a *Arguments) Convert() *agent.Config {
+	return &agent.Config{}
+}

docs/sources/flow/reference/components/prometheus.exporter.agent.md

@@ -0,0 +1,68 @@
+---
+canonical: https://grafana.com/docs/agent/latest/flow/reference/components/prometheus.exporter.agent/
+title: prometheus.exporter.agen
+---
+
+# prometheus.exporter.agent
+The `prometheus.exporter.agent` component collects and exposes metrics about the agent itself.
+
+## Usage
+
+```river
+prometheus.exporter.agent "agent" {
+}
+```
+
+## Arguments
+`prometheus.exporter.agent` accepts no arguments.
+
+## Exported fields
+
+{{< docs/shared lookup="flow/reference/components/exporters-component-exports.md" source="agent" version="<AGENT VERSION>" >}}
+
+## Component health
+
+`prometheus.exporter.agent` is only reported as unhealthy if given
+an invalid configuration.
+
+## Debug information
+
+`prometheus.exporter.agent` does not expose any component-specific
+debug information.
+
+## Debug metrics
+
+`prometheus.exporter.agent` does not expose any component-specific
+debug metrics.
+
+## Example
+
+This example uses a [`prometheus.scrape` component][scrape] to collect metrics
+from `prometheus.exporter.agent`:
+
+```river
+prometheus.exporter.agent "agent" {}
+
+// Configure a prometheus.scrape component to collect agent metrics.
+prometheus.scrape "demo" {
+  targets    = prometheus.exporter.agent.example.targets
+  forward_to = [prometheus.remote_write.demo.receiver]
+}
+
+prometheus.remote_write "demo" {
+  endpoint {
+    url = PROMETHEUS_REMOTE_WRITE_URL
+
+    basic_auth {
+      username = USERNAME
+      password = PASSWORD
+    }
+  }
+}
+```
+Replace the following:
+  - `PROMETHEUS_REMOTE_WRITE_URL`: The URL of the Prometheus remote_write-compatible server to send metrics to.
+  - `USERNAME`: The username to use for authentication to the remote_write API.
+  - `PASSWORD`: The password to use for authentication to the remote_write API.
+
+[scrape]: {{< relref "./prometheus.scrape.md" >}}