From 56a0b058c1ae9a6a045cb145990702df8bc8cce0 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 8 Dec 2020 01:54:13 +0200
Subject: [PATCH] lib/promscrape: export
 `vm_promscrape_active_scrapers{type="<sd_type>"}` metric for tracking the
 number of active scrapers per each service discovery type

---
 docs/CHANGELOG.md         |  1 +
 lib/promscrape/scraper.go | 26 ++++++++++++++++----------
 2 files changed, 17 insertions(+), 10 deletions(-)

diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 3734f9d668..539d0150cf 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -5,6 +5,7 @@
 * FEATURE: allow multiple whitespace chars between measurements, fields and timestamp when parsing InfluxDB line protocol.
   Though [InfluxDB line protocol](https://docs.influxdata.com/influxdb/v1.8/write_protocols/line_protocol_tutorial/) denies multiple whitespace chars between these entities,
   some apps improperly put multiple whitespace chars. This workaround allows accepting data from such apps.
+* FEATURE: export `vm_promscrape_active_scrapers{type="<sd_type>"}` metric for tracking the number of active scrapers per each service discovery type.
 
 * BUGFIX: prevent from duplicate `name` tag returned from `/tags/autoComplete/tags` handler. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/942
 * BUGFIX: do not enable strict parsing for `-promscrape.config` if `-promscrape.config.dryRun` comand-line flag is set. Strict parsing can be enabled with `-promscrape.config.strictParse` command-line flag. See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/944
diff --git a/lib/promscrape/scraper.go b/lib/promscrape/scraper.go
index ccb0d4aaff..db5f3dde3a 100644
--- a/lib/promscrape/scraper.go
+++ b/lib/promscrape/scraper.go
@@ -244,20 +244,24 @@ func (scfg *scrapeConfig) run() {
 }
 
 type scraperGroup struct {
-	name         string
-	wg           sync.WaitGroup
-	mLock        sync.Mutex
-	m            map[string]*scraper
-	pushData     func(wr *prompbmarshal.WriteRequest)
-	changesCount *metrics.Counter
+	name     string
+	wg       sync.WaitGroup
+	mLock    sync.Mutex
+	m        map[string]*scraper
+	pushData func(wr *prompbmarshal.WriteRequest)
+
+	changesCount   *metrics.Counter
+	activeScrapers *metrics.Counter
 }
 
 func newScraperGroup(name string, pushData func(wr *prompbmarshal.WriteRequest)) *scraperGroup {
 	sg := &scraperGroup{
-		name:         name,
-		m:            make(map[string]*scraper),
-		pushData:     pushData,
-		changesCount: metrics.NewCounter(fmt.Sprintf(`vm_promscrape_config_changes_total{type=%q}`, name)),
+		name:     name,
+		m:        make(map[string]*scraper),
+		pushData: pushData,
+
+		changesCount:   metrics.NewCounter(fmt.Sprintf(`vm_promscrape_config_changes_total{type=%q}`, name)),
+		activeScrapers: metrics.NewCounter(fmt.Sprintf(`vm_promscrape_active_scrapers{type=%q}`, name)),
 	}
 	metrics.NewGauge(fmt.Sprintf(`vm_promscrape_targets{type=%q, status="up"}`, name), func() float64 {
 		return float64(tsmGlobal.StatusByGroup(sg.name, true))
@@ -308,11 +312,13 @@ func (sg *scraperGroup) update(sws []ScrapeWork) {
 
 		// Start a scraper for the missing key.
 		sc := newScraper(sw, sg.name, sg.pushData)
+		sg.activeScrapers.Inc()
 		sg.wg.Add(1)
 		go func() {
 			defer sg.wg.Done()
 			sc.sw.run(sc.stopCh)
 			tsmGlobal.Unregister(sw)
+			sg.activeScrapers.Dec()
 		}()
 		tsmGlobal.Register(sw)
 		sg.m[key] = sc