app/vmagent: expose -promscrape.config contents at /config page as Prometheus does

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1695

app/vmagent/main.go

@@ -159,6 +159,7 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 		httpserver.WriteAPIHelp(w, [][2]string{
 			{"/targets", "discovered targets list"},
 			{"/api/v1/targets", "advanced information about discovered targets in JSON format"},
+			{"/config", "-promscrape.config contents"},
 			{"/metrics", "available service metrics"},
 			{"/-/reload", "reload configuration"},
 		})
@@ -259,6 +260,11 @@ func requestHandler(w http.ResponseWriter, r *http.Request) bool {
 		promscrapeTargetsRequests.Inc()
 		promscrape.WriteHumanReadableTargetsStatus(w, r)
 		return true
+	case "/config":
+		promscrapeConfigRequests.Inc()
+		w.Header().Set("Content-Type", "text/plain; charset=utf-8")
+		promscrape.WriteConfigData(w)
+		return true
 	case "/api/v1/targets":
 		promscrapeAPIV1TargetsRequests.Inc()
 		w.Header().Set("Content-Type", "application/json; charset=utf-8")
@@ -427,6 +433,8 @@ var (
 	promscrapeTargetsRequests      = metrics.NewCounter(`vmagent_http_requests_total{path="/targets"}`)
 	promscrapeAPIV1TargetsRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/api/v1/targets"}`)
 
+	promscrapeConfigRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/config"}`)
+
 	promscrapeConfigReloadRequests = metrics.NewCounter(`vmagent_http_requests_total{path="/-/reload"}`)
 )
 

docs/CHANGELOG.md

@@ -6,6 +6,7 @@ sort: 15
 
 ## tip
 
+* FEATURE: vmagent: expose `-promscrape.config` contents at `/config` page as Prometheus does. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/1695).
 * FEATURE: add trigonometric functions, which are going to be added in [Prometheus 2.31](https://github.com/prometheus/prometheus/pull/9239): [acosh](https://docs.victoriametrics.com/MetricsQL.html#acosh), [asinh](https://docs.victoriametrics.com/MetricsQL.html#asinh), [atan](https://docs.victoriametrics.com/MetricsQL.html#atan), [atanh](https://docs.victoriametrics.com/MetricsQL.html#atanh), [cosh](https://docs.victoriametrics.com/MetricsQL.html#cosh), [deg](https://docs.victoriametrics.com/MetricsQL.html#deg), [rad](https://docs.victoriametrics.com/MetricsQL.html#rad), [sinh](https://docs.victoriametrics.com/MetricsQL.html#sinh), [tan](https://docs.victoriametrics.com/MetricsQL.html#tan), [tanh](https://docs.victoriametrics.com/MetricsQL.html#tanh). Also add `atan2` binary operator. See [this pull request](https://github.com/prometheus/prometheus/pull/9248).
 * FEATURE: consistently return the same set of time series from [limitk](https://docs.victoriametrics.com/MetricsQL.html#limitk) function. This improves the usability of periodically refreshed graphs.
 

lib/promscrape/config.go

@@ -58,8 +58,8 @@ var (
 // Config represents essential parts from Prometheus config defined at https://prometheus.io/docs/prometheus/latest/configuration/configuration/
 type Config struct {
 	Global            GlobalConfig   `yaml:"global,omitempty"`
-	ScrapeConfigs     []ScrapeConfig `yaml:"scrape_configs"`
-	ScrapeConfigFiles []string       `yaml:"scrape_config_files"`
+	ScrapeConfigs     []ScrapeConfig `yaml:"scrape_configs,omitempty"`
+	ScrapeConfigFiles []string       `yaml:"scrape_config_files,omitempty"`
 
 	// This is set to the directory from where the config has been loaded.
 	baseDir string
@@ -121,7 +121,7 @@ type ScrapeConfig struct {
 	MetricsPath          string                      `yaml:"metrics_path,omitempty"`
 	HonorLabels          bool                        `yaml:"honor_labels,omitempty"`
 	HonorTimestamps      bool                        `yaml:"honor_timestamps,omitempty"`
-	FollowRedirects      *bool                       `yaml:"follow_redirects"` // omitempty isn't set, since the default value for this flag is true.
+	FollowRedirects      *bool                       `yaml:"follow_redirects,omitempty"`
 	Scheme               string                      `yaml:"scheme,omitempty"`
 	Params               map[string][]string         `yaml:"params,omitempty"`
 	HTTPClientConfig     promauth.HTTPClientConfig   `yaml:",inline"`

lib/promscrape/scraper.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"flag"
 	"fmt"
+	"io"
 	"sync"
 	"sync/atomic"
 	"time"
@@ -70,8 +71,22 @@ var (
 	// PendingScrapeConfigs - zero value means, that
 	// all scrapeConfigs are inited and ready for work.
 	PendingScrapeConfigs int32
+
+	// configData contains -promscrape.config data
+	configData atomic.Value
 )
 
+// WriteConfigData writes -promscrape.config contents to w
+func WriteConfigData(w io.Writer) {
+	v := configData.Load()
+	if v == nil {
+		// Nothing to write to w
+		return
+	}
+	b := v.(*[]byte)
+	w.Write(*b)
+}
+
 func runScraper(configFile string, pushData func(wr *prompbmarshal.WriteRequest), globalStopCh <-chan struct{}) {
 	if configFile == "" {
 		// Nothing to scrape.
@@ -89,6 +104,7 @@ func runScraper(configFile string, pushData func(wr *prompbmarshal.WriteRequest)
 		logger.Fatalf("cannot read %q: %s", configFile, err)
 	}
 	data := cfg.marshal()
+	configData.Store(&data)
 	cfg.mustStart()
 
 	scs := newScrapeConfigs(pushData)
@@ -132,6 +148,7 @@ func runScraper(configFile string, pushData func(wr *prompbmarshal.WriteRequest)
 			cfgNew.mustStart()
 			cfg = cfgNew
 			data = dataNew
+			configData.Store(&data)
 		case <-tickerCh:
 			cfgNew, err := loadConfig(configFile)
 			if err != nil {
@@ -147,6 +164,7 @@ func runScraper(configFile string, pushData func(wr *prompbmarshal.WriteRequest)
 			cfgNew.mustStart()
 			cfg = cfgNew
 			data = dataNew
+			configData.Store(&data)
 		case <-globalStopCh:
 			cfg.mustStop()
 			logger.Infof("stopping Prometheus scrapers")