lib/promscrape: add external_labels from global section of -promscrape.config after the relabeling is applied to the scraped metrics

This aligns with Prometheus behaviour.

See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3137

docs/CHANGELOG.md

@@ -46,6 +46,7 @@ See [these docs](https://docs.victoriametrics.com/Cluster-VictoriaMetrics.html#m
 * FEATURE: [vmgateway](https://docs.victoriametrics.com/vmgateway.html): add ability to extract JWT authorization token from non-standard HTTP header by passing it via `-auth.httpHeader` command-line flag. See [this feature request](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3054).
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): expose `__meta_ec2_region` label for [ec2_sd_config](https://docs.victoriametrics.com/sd_configs.html#ec2_sd_configs) in the same way as [Prometheus 2.39 does](https://github.com/prometheus/prometheus/pull/11326).
 * FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): accept data ingestion requests via paths starting from `/prometheus` prefix in the same way as [VictoriaMetrics does](https://docs.victoriametrics.com/#how-to-import-time-series-data). For example, `vmagent` now accepts Prometheus `remote_write` data via both `/api/v1/write` and `/prometheus/api/v1/write`. This simplifies switching between single-node VictoriaMetrics and `vmagent`.
+* FEATURE: [vmagent](https://docs.victoriametrics.com/vmagent.html): add `external_labels` from `global` section at `-promscrape.config` after the [relabeling](https://docs.victoriametrics.com/vmagent.html#relabeling) is applied to scraped metrics. This aligns with Prometheus behaviour. Previously the `external_labels` were added to scrape targets, so they could be modified during relabeling. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3137).
 
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly encode query params for aws signed requests, use `%20` instead of `+` as api requires. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3171).
 * BUGFIX: [vmagent](https://docs.victoriametrics.com/vmagent.html): properly parse relabel config when regex ending with escaped `$`. See [this issue](https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3131).

lib/promscrape/config.go

@@ -229,6 +229,22 @@ type GlobalConfig struct {
 	ExternalLabels map[string]string   `yaml:"external_labels,omitempty"`
 }
 
+func (gc *GlobalConfig) getExternalLabels() []prompbmarshal.Label {
+	externalLabels := gc.ExternalLabels
+	if len(externalLabels) == 0 {
+		return nil
+	}
+	labels := make([]prompbmarshal.Label, 0, len(externalLabels))
+	for name, value := range externalLabels {
+		labels = append(labels, prompbmarshal.Label{
+			Name:  name,
+			Value: value,
+		})
+	}
+	promrelabel.SortLabels(labels)
+	return labels
+}
+
 // ScrapeConfig represents essential parts for `scrape_config` section of Prometheus config.
 //
 // See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config
@@ -933,6 +949,7 @@ func getScrapeWorkConfig(sc *ScrapeConfig, baseDir string, globalCfg *GlobalConf
 	if (*streamParse || sc.StreamParse) && sc.SeriesLimit > 0 {
 		return nil, fmt.Errorf("cannot use stream parsing mode when `series_limit` is set for `job_name` %q", jobName)
 	}
+	externalLabels := globalCfg.getExternalLabels()
 	swc := &scrapeWorkConfig{
 		scrapeInterval:       scrapeInterval,
 		scrapeIntervalString: scrapeInterval.String(),
@@ -948,7 +965,7 @@ func getScrapeWorkConfig(sc *ScrapeConfig, baseDir string, globalCfg *GlobalConf
 		honorLabels:          honorLabels,
 		honorTimestamps:      honorTimestamps,
 		denyRedirects:        denyRedirects,
-		externalLabels:       globalCfg.ExternalLabels,
+		externalLabels:       externalLabels,
 		relabelConfigs:       relabelConfigs,
 		metricRelabelConfigs: metricRelabelConfigs,
 		sampleLimit:          sc.SampleLimit,
@@ -977,7 +994,7 @@ type scrapeWorkConfig struct {
 	honorLabels          bool
 	honorTimestamps      bool
 	denyRedirects        bool
-	externalLabels       map[string]string
+	externalLabels       []prompbmarshal.Label
 	relabelConfigs       *promrelabel.ParsedConfigs
 	metricRelabelConfigs *promrelabel.ParsedConfigs
 	sampleLimit          int
@@ -1308,6 +1325,7 @@ func (swc *scrapeWorkConfig) getScrapeWork(target string, extraLabels, metaLabel
 		DenyRedirects:        swc.denyRedirects,
 		OriginalLabels:       originalLabels,
 		Labels:               labels,
+		ExternalLabels:       swc.externalLabels,
 		ProxyURL:             swc.proxyURL,
 		ProxyAuthConfig:      swc.proxyAuthConfig,
 		AuthConfig:           swc.authConfig,
@@ -1357,9 +1375,6 @@ func mergeLabels(dst []prompbmarshal.Label, swc *scrapeWorkConfig, target string
 		logger.Panicf("BUG: len(dst) must be 0; got %d", len(dst))
 	}
 	// See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#relabel_config
-	for k, v := range swc.externalLabels {
-		dst = appendLabel(dst, k, v)
-	}
 	dst = appendLabel(dst, "job", swc.jobName)
 	dst = appendLabel(dst, "__address__", target)
 	dst = appendLabel(dst, "__scheme__", swc.scheme)

lib/promscrape/config_test.go

@@ -36,19 +36,11 @@ func TestMergeLabels(t *testing.T) {
 		metricsPath:          "/foo/bar",
 		scrapeIntervalString: "15s",
 		scrapeTimeoutString:  "10s",
-		externalLabels: map[string]string{
-			"job": "bar",
-			"a":   "b",
-		},
-	}, "foo", nil, nil, `{__address__="foo",__metrics_path__="/foo/bar",__scheme__="https",__scrape_interval__="15s",__scrape_timeout__="10s",a="b",job="xyz"}`)
+	}, "foo", nil, nil, `{__address__="foo",__metrics_path__="/foo/bar",__scheme__="https",__scrape_interval__="15s",__scrape_timeout__="10s",job="xyz"}`)
 	f(&scrapeWorkConfig{
 		jobName:     "xyz",
 		scheme:      "https",
 		metricsPath: "/foo/bar",
-		externalLabels: map[string]string{
-			"job": "bar",
-			"a":   "b",
-		},
 	}, "foo", map[string]string{
 		"job": "extra_job",
 		"foo": "extra_foo",
@@ -959,10 +951,6 @@ scrape_configs:
 					Name:  "__scrape_timeout__",
 					Value: "10s",
 				},
-				{
-					Name:  "datacenter",
-					Value: "foobar",
-				},
 				{
 					Name:  "instance",
 					Value: "foo.bar:1234",
@@ -971,6 +959,12 @@ scrape_configs:
 					Name:  "job",
 					Value: "foo",
 				},
+			},
+			ExternalLabels: []prompbmarshal.Label{
+				{
+					Name:  "datacenter",
+					Value: "foobar",
+				},
 				{
 					Name:  "jobs",
 					Value: "xxx",
@@ -1604,6 +1598,24 @@ scrape_configs:
 					Name:  "job",
 					Value: "yyy",
 				},
+			},
+			ExternalLabels: []prompbmarshal.Label{
+				{
+					Name:  "__address__",
+					Value: "aaasdf",
+				},
+				{
+					Name:  "__param_a",
+					Value: "jlfd",
+				},
+				{
+					Name:  "foo",
+					Value: "xx",
+				},
+				{
+					Name:  "job",
+					Value: "foobar",
+				},
 				{
 					Name:  "q",
 					Value: "qwe",

lib/promscrape/scrapework.go

@@ -87,6 +87,12 @@ type ScrapeWork struct {
 	// See also https://prometheus.io/docs/concepts/jobs_instances/
 	Labels []prompbmarshal.Label
 
+	// ExternalLabels contains labels from global->external_labels section of -promscrape.config
+	//
+	// These labels are added to scraped metrics after the relabeling.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3137
+	ExternalLabels []prompbmarshal.Label
+
 	// ProxyURL HTTP proxy url
 	ProxyURL *proxy.URL
 
@@ -140,9 +146,11 @@ func (sw *ScrapeWork) key() string {
 	// Do not take into account OriginalLabels, since they can be changed with relabeling.
 	// Take into account JobNameOriginal in order to capture the case when the original job_name is changed via relabeling.
 	key := fmt.Sprintf("JobNameOriginal=%s, ScrapeURL=%s, ScrapeInterval=%s, ScrapeTimeout=%s, HonorLabels=%v, HonorTimestamps=%v, DenyRedirects=%v, Labels=%s, "+
+		"ExternalLabels=%s, "+
 		"ProxyURL=%s, ProxyAuthConfig=%s, AuthConfig=%s, MetricRelabelConfigs=%s, SampleLimit=%d, DisableCompression=%v, DisableKeepAlive=%v, StreamParse=%v, "+
 		"ScrapeAlignInterval=%s, ScrapeOffset=%s, SeriesLimit=%d",
 		sw.jobNameOriginal, sw.ScrapeURL, sw.ScrapeInterval, sw.ScrapeTimeout, sw.HonorLabels, sw.HonorTimestamps, sw.DenyRedirects, sw.LabelsString(),
+		promLabelsString(sw.ExternalLabels),
 		sw.ProxyURL.String(), sw.ProxyAuthConfig.String(),
 		sw.AuthConfig.String(), sw.MetricRelabelConfigs.String(), sw.SampleLimit, sw.DisableCompression, sw.DisableKeepAlive, sw.StreamParse,
 		sw.ScrapeAlignInterval, sw.ScrapeOffset, sw.SeriesLimit)
@@ -835,6 +843,9 @@ func (sw *scrapeWork) addRowToTimeseries(wc *writeRequestCtx, r *parser.Row, tim
 		// Skip row without labels.
 		return
 	}
+	// Add labels from `global->external_labels` section after the relabeling like Prometheus does.
+	// See https://github.com/VictoriaMetrics/VictoriaMetrics/issues/3137
+	wc.labels = appendExtraLabels(wc.labels, sw.Config.ExternalLabels, labelsLen, sw.Config.HonorLabels)
 	sampleTimestamp := r.Timestamp
 	if !sw.Config.HonorTimestamps || sampleTimestamp == 0 {
 		sampleTimestamp = timestamp
@@ -863,36 +874,43 @@ func appendLabels(dst []prompbmarshal.Label, metric string, src []parser.Tag, ex
 			Value: tag.Value,
 		})
 	}
-	dst = append(dst, extraLabels...)
-	labels := dst[dstLen:]
-	if len(labels) <= 1 {
-		// Fast path - only a single label.
+	return appendExtraLabels(dst, extraLabels, dstLen, honorLabels)
+}
+
+func appendExtraLabels(dst, extraLabels []prompbmarshal.Label, offset int, honorLabels bool) []prompbmarshal.Label {
+	// Add extraLabels to labels.
+	// Handle duplicates in the same way as Prometheus does.
+	if len(dst) > offset && dst[offset].Name == "__name__" {
+		offset++
+	}
+	labels := dst[offset:]
+	if len(labels) == 0 {
+		// Fast path - add extraLabels to dst without the need to de-duplicate.
+		dst = append(dst, extraLabels...)
 		return dst
 	}
-
-	// de-duplicate labels
-	dstLabels := labels[:0]
-	for i := range labels {
-		label := &labels[i]
-		prevLabel := promrelabel.GetLabelByName(dstLabels, label.Name)
+	for _, label := range extraLabels {
+		prevLabel := promrelabel.GetLabelByName(labels, label.Name)
 		if prevLabel == nil {
-			dstLabels = append(dstLabels, *label)
+			// Fast path - the label doesn't exist in labels, so just add it to dst.
+			dst = append(dst, label)
 			continue
 		}
 		if honorLabels {
 			// Skip the extra label with the same name.
 			continue
 		}
-		// Rename the prevLabel to "exported_" + label.Name.
+		// Rename the prevLabel to "exported_" + label.Name
 		// See https://prometheus.io/docs/prometheus/latest/configuration/configuration/#scrape_config
 		exportedName := "exported_" + label.Name
-		if promrelabel.GetLabelByName(dstLabels, exportedName) != nil {
-			// Override duplicate with the current label.
-			*prevLabel = *label
-			continue
+		exportedLabel := promrelabel.GetLabelByName(labels, exportedName)
+		if exportedLabel == nil {
+			prevLabel.Name = exportedName
+			dst = append(dst, label)
+		} else {
+			exportedLabel.Value = prevLabel.Value
+			prevLabel.Value = label.Value
 		}
-		prevLabel.Name = exportedName
-		dstLabels = append(dstLabels, *label)
 	}
-	return dst[:dstLen+len(dstLabels)]
+	return dst
 }

lib/promscrape/scrapework_test.go

@@ -12,6 +12,33 @@ import (
 	parser "github.com/VictoriaMetrics/VictoriaMetrics/lib/protoparser/prometheus"
 )
 
+func TestAppendExtraLabels(t *testing.T) {
+	f := func(sourceLabels, extraLabels string, honorLabels bool, resultExpected string) {
+		t.Helper()
+		src := promrelabel.MustParseMetricWithLabels(sourceLabels)
+		extra := promrelabel.MustParseMetricWithLabels(extraLabels)
+		labels := appendExtraLabels(src, extra, 0, honorLabels)
+		result := promLabelsString(labels)
+		if result != resultExpected {
+			t.Fatalf("unexpected result; got\n%s\nwant\n%s", result, resultExpected)
+		}
+	}
+	f("{}", "{}", true, "{}")
+	f("{}", "{}", false, "{}")
+	f("foo", "{}", true, `{__name__="foo"}`)
+	f("foo", "{}", false, `{__name__="foo"}`)
+	f("foo", "bar", true, `{__name__="foo",__name__="bar"}`)
+	f("foo", "bar", false, `{__name__="foo",__name__="bar"}`)
+	f(`{a="b"}`, `{c="d"}`, true, `{a="b",c="d"}`)
+	f(`{a="b"}`, `{c="d"}`, false, `{a="b",c="d"}`)
+	f(`{a="b"}`, `{a="d"}`, true, `{a="b"}`)
+	f(`{a="b"}`, `{a="d"}`, false, `{exported_a="b",a="d"}`)
+	f(`{a="b",exported_a="x"}`, `{a="d"}`, true, `{a="b",exported_a="x"}`)
+	f(`{a="b",exported_a="x"}`, `{a="d"}`, false, `{a="d",exported_a="b"}`)
+	f(`{a="b"}`, `{a="d",exported_a="x"}`, true, `{a="b",exported_a="x"}`)
+	f(`{a="b"}`, `{a="d",exported_a="x"}`, false, `{exported_a="b",a="d",exported_a="x"}`)
+}
+
 func TestPromLabelsString(t *testing.T) {
 	f := func(labels []prompbmarshal.Label, resultExpected string) {
 		t.Helper()
@@ -187,7 +214,7 @@ func TestScrapeWorkScrapeInternalSuccess(t *testing.T) {
 	`)
 	f(`
 		foo{job="orig",bar="baz"} 34.45
-		bar{y="2",job="aa",a="b",job="bb",x="1"} -3e4 2345
+		bar{y="2",job="aa",a="b",x="1"} -3e4 2345
 	`, &ScrapeWork{
 		ScrapeTimeout: time.Second * 42,
 		HonorLabels:   false,
@@ -262,7 +289,7 @@ func TestScrapeWorkScrapeInternalSuccess(t *testing.T) {
 	`)
 	f(`
 		foo{job="orig",bar="baz"} 34.45
-		bar{job="aa",a="b",job="bb"} -3e4 2345
+		bar{job="aa",a="b"} -3e4 2345
 	`, &ScrapeWork{
 		ScrapeTimeout: time.Second * 42,
 		HonorLabels:   true,