Add docs and fix for test component

component/all/all.go

@@ -125,6 +125,7 @@ import (
 	_ "github.com/grafana/agent/component/prometheus/relabel"                       // Import prometheus.relabel
 	_ "github.com/grafana/agent/component/prometheus/remotewrite"                   // Import prometheus.remote_write
 	_ "github.com/grafana/agent/component/prometheus/scrape"                        // Import prometheus.scrape
+	_ "github.com/grafana/agent/component/prometheus/test/metrics"                  // Import prometheus.test.metrics
 	_ "github.com/grafana/agent/component/pyroscope/ebpf"                           // Import pyroscope.ebpf
 	_ "github.com/grafana/agent/component/pyroscope/scrape"                         // Import pyroscope.scrape
 	_ "github.com/grafana/agent/component/pyroscope/write"                          // Import pyroscope.write

component/prometheus/test/metrics/component.go

@@ -11,7 +11,6 @@ import (
 	"sync"
 	"time"
 
-	"github.com/golang/snappy"
 	"github.com/gorilla/mux"
 
 	"github.com/grafana/agent/component"
@@ -23,8 +22,6 @@ func init() {
 		Name:    "prometheus.test.metrics",
 		Args:    Arguments{},
 		Exports: Exports{},
-
-		NeedsServices: []string{http.ServiceName},
 		Build: func(opts component.Options, args component.Arguments) (component.Component, error) {
 			return NewComponent(opts, args.(Arguments))
 		},
@@ -34,8 +31,9 @@ func init() {
 type Component struct {
 	mut        sync.Mutex
 	args       Arguments
+	o          component.Options
 	instances  []*instance
-	argsUpdate chan struct{}
+	argsUpdate chan Arguments
 	path       string
 	handler    http.Data
 }
@@ -66,7 +64,6 @@ func (c *Component) serveMetrics(w httpgo.ResponseWriter, r *httpgo.Request) {
 		w.WriteHeader(httpgo.StatusNotFound)
 		return
 	}
-	w.Header().Set("Content-Encoding", "snappy")
 	_, _ = w.Write(c.instances[id].buffer())
 }
 
@@ -78,16 +75,18 @@ func NewComponent(o component.Options, c Arguments) (*Component, error) {
 	httpData := data.(http.Data)
 	fullpath := httpData.HTTPPathForComponent(o.ID)
 	return &Component{
+		o:          o,
 		args:       c,
 		path:       fullpath,
-		argsUpdate: make(chan struct{}),
+		argsUpdate: make(chan Arguments),
 		instances:  make([]*instance, 0),
 		handler:    httpData,
 	}, nil
 }
 
 func (c *Component) Run(ctx context.Context) error {
-	c.generateNewSet(true)
+	forceNewSet := true
+	c.generateNewSet(forceNewSet)
 	for {
 		c.mut.Lock()
 		t := time.NewTicker(c.args.MetricsRefresh)
@@ -97,11 +96,14 @@ func (c *Component) Run(ctx context.Context) error {
 			return nil
 		case <-t.C:
 			{
-				c.generateNewSet(false)
+				c.generateNewSet(forceNewSet)
+				forceNewSet = false
 			}
-		case <-c.argsUpdate:
+		case a := <-c.argsUpdate:
 			{
-				// Mainly to update the args.
+				// If instance count changed we need to force a new update
+				forceNewSet = a.NumberOfInstances != c.args.NumberOfInstances
+				c.args = a
 			}
 		}
 	}
@@ -111,11 +113,22 @@ func (c *Component) Update(args component.Arguments) error {
 	c.mut.Lock()
 	defer c.mut.Unlock()
 
-	c.args = args.(Arguments)
-	c.argsUpdate <- struct{}{}
+	c.argsUpdate <- args.(Arguments)
 	return nil
 }
 
+func (c *Component) generateDiscovery() []byte {
+	c.mut.Lock()
+	defer c.mut.Unlock()
+
+	instances := make([]target, len(c.instances))
+	for x := range c.instances {
+		instances[x] = createTarget(c.handler.HTTPListenAddr, c.path+fmt.Sprintf("instance/%d/metrics", x))
+	}
+	marshalledBytes, _ := json.Marshal(instances)
+	return marshalledBytes
+}
+
 type Arguments struct {
 	NumberOfInstances int           `river:"number_of_instances,attr"`
 	NumberOfMetrics   int           `river:"number_of_metrics,attr"`
@@ -124,11 +137,26 @@ type Arguments struct {
 	ChurnPercent      float32       `river:"churn_percent,attr"`
 }
 
+func getDefault() Arguments {
+	return Arguments{
+		NumberOfInstances: 1,
+		NumberOfMetrics:   1,
+		NumberOfSeries:    1,
+		MetricsRefresh:    1 * time.Minute,
+		ChurnPercent:      0,
+	}
+}
+
+// SetToDefault implements river.Defaulter.
+func (a *Arguments) SetToDefault() {
+	*a = getDefault()
+}
+
 type Exports struct {
 	Targets []map[string]string `river:"targets,attr,optional"`
 }
 
-// generateNewSet  creates the buffers of data. forceNewInstances instatiates all new buffers.
+// generateNewSet  creates the buffers of data. forceNewInstances instantiates all new buffers.
 func (c *Component) generateNewSet(forceNewInstances bool) {
 	c.mut.Lock()
 	defer c.mut.Unlock()
@@ -150,6 +178,15 @@ func (c *Component) generateNewSet(forceNewInstances bool) {
 	for _, i := range c.instances {
 		i.generateData(c.args.NumberOfSeries)
 	}
+	if forceNewInstances {
+		targets := make([]map[string]string, len(c.instances))
+		for x, _ := range c.instances {
+			targets[x] = make(map[string]string)
+			targets[x]["__address__"] = c.handler.HTTPListenAddr
+			targets[x]["__metrics_path__"] = c.path + fmt.Sprintf("instance/%d/metrics", x)
+		}
+		c.o.OnStateChange(Exports{Targets: targets})
+	}
 }
 
 func (c *Component) data() [][]byte {
@@ -211,7 +248,7 @@ func (i *instance) generateData(seriesCount int) {
 		buf.WriteString(lblstring)
 		buf.WriteString("} 1\n")
 	}
-	i.buf = snappy.Encode(nil, buf.Bytes())
+	i.buf = buf.Bytes()
 }
 
 func createTarget(host, path string) target {

component/prometheus/test/metrics/component_test.go

@@ -3,20 +3,20 @@ package metrics
 import (
 	"context"
 	"fmt"
-	"github.com/golang/snappy"
+	"net"
+	"strings"
+	"testing"
+	"time"
+
 	"github.com/grafana/agent/component"
 	"github.com/grafana/agent/pkg/util"
 	http_service "github.com/grafana/agent/service/http"
 	"github.com/grafana/agent/service/labelstore"
 	prometheus_client "github.com/prometheus/client_golang/prometheus"
 	"github.com/stretchr/testify/require"
-	"net"
-	"strings"
-	"testing"
-	"time"
 )
 
-func TestMetrcsGeneration(t *testing.T) {
+func TestMetricsGeneration(t *testing.T) {
 	opts := component.Options{
 		Logger:     util.TestFlowLogger(t),
 		Registerer: prometheus_client.NewRegistry(),
@@ -35,6 +35,9 @@ func TestMetrcsGeneration(t *testing.T) {
 				return nil, fmt.Errorf("service %q does not exist", name)
 			}
 		},
+		OnStateChange: func(e component.Exports) {
+
+		},
 	}
 
 	s, err := NewComponent(opts, Arguments{
@@ -55,9 +58,7 @@ func TestMetrcsGeneration(t *testing.T) {
 		return len(bb) > 0 && len(bb[0]) > 2
 	}, 10*time.Second, 100*time.Millisecond)
 	require.Len(t, bb, 1)
-	out, err := snappy.Decode(nil, bb[0])
-	require.NoError(t, err)
-	metrics := string(out)
+	metrics := string(bb[0])
 	require.True(t, strings.Contains(metrics, "counter"))
 	require.True(t, strings.Contains(metrics, "agent_metric_test_0"))
 

docs/sources/flow/reference/components/prometheus.test.metrics.md

@@ -0,0 +1,83 @@
+---
+aliases:
+- /docs/grafana-cloud/agent/flow/reference/components/prometheus.test.metrics/
+canonical: https://grafana.com/docs/agent/latest/flow/reference/components/prometheus.test.metrics/
+description: Learn about prometheus.test.metrics  
+labels:
+  stage: experimental
+title: prometheus.test.metrics
+---
+
+# prometheus.test.metrics
+
+
+`prometheus.test.metrics` configures a locally hosted service discovery that then exposes endpoints 
+for collecting generated metrics. It is best used for testing perfomance and will always be considered
+experimental.
+
+Multiple `prometheus.test.metrics` components can be specified by giving them
+different labels.
+
+## Usage
+
+```
+prometheus.test.metrics "LABEL" {
+}
+```
+
+## Arguments
+
+The following arguments are supported:
+
+Name | Type | Description | Default | Required
+---- | ---- | ----------- | ------- | --------
+`number_of_instances` | `int`     | Number of instances to provide. | `1` | no
+`number_of_metrics` | `int`     | Number of metrics to provide. | `1` | no  
+`number_of_labels` | `int`     | Number of labels to provide per metric. | `0` | no
+`metrics_refresh` | `duration`     | How often to refresh metrics and labels. | `1m` | no  
+`churn_percent` | `float`     | What percentage of metrics to churn during a refresh, must be between 0 and 1. | `0` | no  
+
+## Exported fields
+
+The following fields are exported and can be referenced by other components:
+
+Name      | Type                | Description
+--------- | ------------------- | -----------
+`targets` | `list(map(string))` | The set of targets discovered from the component.
+
+
+## Component health
+
+`prometheus.test.metrics` is only reported as unhealthy if given an invalid
+configuration.
+
+## Example
+
+```river
+
+prometheus.test.metrics "single" {
+    number_of_instances = 1
+    number_of_metrics = 1000
+    number_of_labels = 5
+    metrics_refresh = "10m"
+    churn_percent = 0.05
+}
+
+prometheus.scrape "default" {
+  targets = concat(prometheus.test.metrics.single.targets)
+  forward_to = [prometheus.remote_write.default.receiver]
+}
+
+
+prometheus.remote_write "default" {
+    endpoint {
+        url = "http://mimir:9009/api/v1/push"
+        basic_auth {
+            username = "example-user"
+            password = "example-password"
+        } 
+    }
+}
+```
+
+