prometheus.scrape: add options for enabling native histograms scraping (

#5335)

Signed-off-by: Paschalis Tsilias <paschalis.tsilias@grafana.com>

CHANGELOG.md

@@ -76,6 +76,8 @@ Main (unreleased)
   This will load all River files in the directory as a single configuration;
   component names must be unique across all loaded files. (@rfratto, @hainenber)
 
+- Flow: the `prometheus.scrape` component can now configure the scraping of
+  Prometheus native histograms. (@tpaschalis)
 
 ### Enhancements
 

component/prometheus/scrape/scrape.go

@@ -53,6 +53,8 @@ type Arguments struct {
 	HonorTimestamps bool `river:"honor_timestamps,attr,optional"`
 	// A set of query parameters with which the target is scraped.
 	Params url.Values `river:"params,attr,optional"`
+	// Whether to scrape a classic histogram that is also exposed as a native histogram.
+	ScrapeClassicHistograms bool `river:"scrape_classic_histogram,attr,optional"`
 	// How frequently to scrape the targets of this scrape config.
 	ScrapeInterval time.Duration `river:"scrape_interval,attr,optional"`
 	// The timeout for scraping targets of this config.
@@ -83,7 +85,8 @@ type Arguments struct {
 	HTTPClientConfig component_config.HTTPClientConfig `river:",squash"`
 
 	// Scrape Options
-	ExtraMetrics bool `river:"extra_metrics,attr,optional"`
+	ExtraMetrics              bool `river:"extra_metrics,attr,optional"`
+	EnableProtobufNegotiation bool `river:"enable_protobuf_negotiation,attr,optional"`
 
 	Clustering Clustering `river:"clustering,block,optional"`
 }
@@ -155,6 +158,7 @@ func New(o component.Options, args Arguments) (*Component, error) {
 		HTTPClientOptions: []config_util.HTTPClientOption{
 			config_util.WithDialContextFunc(httpData.DialFunc),
 		},
+		EnableProtobufNegotiation: args.EnableProtobufNegotiation,
 	}
 	scraper := scrape.NewManager(scrapeOptions, o.Logger, flowAppendable)
 
@@ -284,6 +288,7 @@ func getPromScrapeConfigs(jobName string, c Arguments) *config.ScrapeConfig {
 	dec.HonorLabels = c.HonorLabels
 	dec.HonorTimestamps = c.HonorTimestamps
 	dec.Params = c.Params
+	dec.ScrapeClassicHistograms = c.ScrapeClassicHistograms
 	dec.ScrapeInterval = model.Duration(c.ScrapeInterval)
 	dec.ScrapeTimeout = model.Duration(c.ScrapeTimeout)
 	dec.MetricsPath = c.MetricsPath

docs/sources/flow/reference/components/prometheus.scrape.md

@@ -47,9 +47,11 @@ Name | Type | Description | Default | Required
 `forward_to`               | `list(MetricsReceiver)` | List of receivers to send scraped metrics to. | | yes
 `job_name`                 | `string`   | The job name to override the job label with. | component name | no
 `extra_metrics`            | `bool`     | Whether extra metrics should be generated for scrape targets. | `false` | no
+`enable_protobuf_negotiation` | `bool`     | Whether to enable protobuf negotiation with the client. | `false` | no
 `honor_labels`             | `bool`     | Indicator whether the scraped metrics should remain unmodified. | `false` | no
 `honor_timestamps`         | `bool`     | Indicator whether the scraped timestamps should be respected. | `true` | no
 `params`                   | `map(list(string))` | A set of query parameters with which the target is scraped. | | no
+`scrape_classic_histogram` | `bool`     | Whether to scrape a classic histogram that is also exposed as a native histogram. | `false` | no
 `scrape_interval`          | `duration` | How frequently to scrape the targets of this scrape config. | `"60s"` | no
 `scrape_timeout`           | `duration` | The timeout for scraping targets of this config. | `"10s"` | no
 `metrics_path`             | `string`   | The HTTP resource path on which to fetch metrics from targets. | `/metrics` | no
@@ -230,6 +232,12 @@ times out while scraping, or because the samples from the target could not be
 processed. When the target is behaving normally, the `up` metric is set to
 `1`.
 
+To enable scraping of Prometheus' native histograms over gRPC, the
+`enable_protobuf_negotiation` must be set to true. The
+`scrape_classic_histogram` argument controls whether the component should also
+scrape the 'classic' histogram equivalent of a native histogram, if it is
+present.
+
 [in-memory traffic]: {{< relref "../../concepts/component_controller.md#in-memory-traffic" >}}
 [run command]: {{< relref "../cli/run.md" >}}