lib/promscrape: fix honor_labels behavior (#3739)

Co-authored-by: Aliaksandr Valialkin <valyala@victoriametrics.com>

docs/CHANGELOG.md

@@ -34,6 +34,7 @@ The following tip changes can be tested by building VictoriaMetrics components f
 * BUGFIX: [vmui](https://docs.victoriametrics.com/#vmui): add support for time zone selection for older versions of browsers. See [this pull request](https://github.com/VictoriaMetrics/VictoriaMetrics/pull/3680).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): update API version for [ec2_sd_configs](https://docs.victoriametrics.com/sd_configs.html#ec2_sd_configs) to fix [the issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3700) with missing `__meta_ec2_availability_zone_id` attribute.
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly return `200 OK` HTTP status code when importing data via [Pushgateway protocol](https://docs.victoriametrics.com/#how-to-import-data-in-prometheus-exposition-format). See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3636).
+* BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): do not add `exported_` prefix to scraped metric names, which clash with the [automatically generated metric names](https://docs.victoriametrics.com/vmagent.html#automatically-generated-metrics) if `honor_labels: true` option is set in the [scrape_config](https://docs.victoriametrics.com/sd_configs.html#scrape_configs). See the [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3557) and [this](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3406) issues.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth.html): allow re-entering authorization info in the web browser if the entered info was incorrect. Previously it was non-trivial to do via the web browser, since `vmauth` was returning `400 Bad Request` instead of `401 Unauthorized` http response code.
 * BUGFIX: [vmauth](https://docs.victoriametrics.com/vmauth.html): always log the client address and the requested URL on proxying errors. Previously some errors could miss this information.
 * BUGFIX: [vmbackup](https://docs.victoriametrics.com/vmbackup.html): fix snapshot not being deleted after backup completion. This issue could result in unnecessary snapshots being stored, it is required to delete unnecessary snapshots manually. See the [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3735).

lib/promscrape/scrapework.go

@@ -905,12 +905,14 @@ func (sw *scrapeWork) addAutoTimeseries(wc *writeRequestCtx, name string, value
 func (sw *scrapeWork) addRowToTimeseries(wc *writeRequestCtx, r *parser.Row, timestamp int64, needRelabel bool) {
 	metric := r.Metric
 	if needRelabel && isAutoMetric(metric) {
+		if !sw.Config.HonorLabels && len(r.Tags) == 0 {
 			bb := bbPool.Get()
 			bb.B = append(bb.B, "exported_"...)
 			bb.B = append(bb.B, metric...)
 			metric = bytesutil.InternBytes(bb.B)
 			bbPool.Put(bb)
 		}
+	}
 	labelsLen := len(wc.labels)
 	targetLabels := sw.Config.Labels.GetLabels()
 	wc.labels = appendLabels(wc.labels, metric, r.Tags, targetLabels, sw.Config.HonorLabels)

lib/promscrape/scrapework_test.go

@@ -361,9 +361,27 @@ func TestScrapeWorkScrapeInternalSuccess(t *testing.T) {
 	`, &ScrapeWork{
 		ScrapeTimeout: time.Second * 42,
 	}, `
-		exported_up{bar="baz"} 34.44 123
+		up{bar="baz"} 34.44 123
-		exported_scrape_series_added 3.435 123
 		bar{a="b",c="d"} -3e4 123
+		exported_scrape_series_added 3.435 123
+		up 1 123
+		scrape_duration_seconds 0 123
+		scrape_samples_scraped 3 123
+		scrape_samples_post_metric_relabeling 3 123
+		scrape_timeout_seconds 42 123
+		scrape_series_added 3 123
+	`)
+	f(`
+		up{bar="baz"} 34.44
+		bar{a="b",c="d"} -3e4
+		scrape_series_added 3.435
+	`, &ScrapeWork{
+		ScrapeTimeout: time.Second * 42,
+		HonorLabels:   true,
+	}, `
+		up{bar="baz"} 34.44 123
+		bar{a="b",c="d"} -3e4 123
+		scrape_series_added 3.435 123
 		up 1 123
 		scrape_samples_scraped 3 123
 		scrape_duration_seconds 0 123