lib/promrelabel: add support for keepequal and dropequal relabeling actions

These actions are supported by Prometheus starting from v2.41.0

See https://github.com/prometheus/prometheus/pull/11564 ,
https://github.com/prometheus/prometheus/issues/11556
and https://github.com/prometheus/prometheus/issues/3756

Side note:

It's a pity that Prometheus developers decided inventing `keepequal` and `dropequal`
relabeling actions instead of adding support for `keep_if_equal` and `drop_if_equal` relabeling
actions supported by VictoriaMetrics since June 2020 - see 2a39ba639d .

docs/CHANGELOG.md

@@ -15,6 +15,8 @@ The following tip changes can be tested by building VictoriaMetrics components f
 
 ## tip
 
+* FEATURE: [relabeling](https://docs.victoriametrics.com/vmagent.html#relabeling): add support for `keepequal` and `dropequal` relabeling actions, which are supported by Prometheus starting from [v2.41.0](https://github.com/prometheus/prometheus/releases/tag/v2.41.0). These relabeling actions are almost identical to `keep_if_equal` and `drop_if_equal` relabeling actions supported by VictoriaMetrics since `v1.38.0` - see [these docs](https://docs.victoriametrics.com/vmagent.html#relabeling-enhancements) - so it is recommended sticking to `keep_if_equal` and `drop_if_equal` actions instead of switching to `keepequal` and `dropequal`.
+
 
 ## [v1.85.3](https://github.com/VictoriaMetrics/VictoriaMetrics/releases/tag/v1.85.3)
 

lib/promrelabel/config.go

@@ -278,7 +278,7 @@ func parseRelabelConfig(rc *RelabelConfig) (*parsedRelabelConfig, error) {
 			return nil, fmt.Errorf("`replacement` cannot be used with `action=graphite`; see https://docs.victoriametrics.com/vmagent.html#graphite-relabeling")
 		}
 		if rc.Regex != nil {
-			return nil, fmt.Errorf("`regex` cannot be used with `action=graphite`; see https://docs.victoriametrics.com/vmagent.html#graphite-relabeling")
+			return nil, fmt.Errorf("`regex` cannot be used for `action=graphite`; see https://docs.victoriametrics.com/vmagent.html#graphite-relabeling")
 		}
 	case "replace":
 		if targetLabel == "" {
@@ -295,10 +295,36 @@ func parseRelabelConfig(rc *RelabelConfig) (*parsedRelabelConfig, error) {
 		if len(sourceLabels) < 2 {
 			return nil, fmt.Errorf("`source_labels` must contain at least two entries for `action=keep_if_equal`; got %q", sourceLabels)
 		}
+		if targetLabel != "" {
+			return nil, fmt.Errorf("`target_label` cannot be used for `action=keep_if_equal`")
+		}
+		if rc.Regex != nil {
+			return nil, fmt.Errorf("`regex` cannot be used for `action=keep_if_equal`")
+		}
 	case "drop_if_equal":
 		if len(sourceLabels) < 2 {
 			return nil, fmt.Errorf("`source_labels` must contain at least two entries for `action=drop_if_equal`; got %q", sourceLabels)
 		}
+		if targetLabel != "" {
+			return nil, fmt.Errorf("`target_label` cannot be used for `action=drop_if_equal`")
+		}
+		if rc.Regex != nil {
+			return nil, fmt.Errorf("`regex` cannot be used for `action=drop_if_equal`")
+		}
+	case "keepequal":
+		if targetLabel == "" {
+			return nil, fmt.Errorf("missing `target_label` for `action=keepequal`")
+		}
+		if rc.Regex != nil {
+			return nil, fmt.Errorf("`regex` cannot be used for `action=keepequal`")
+		}
+	case "dropequal":
+		if targetLabel == "" {
+			return nil, fmt.Errorf("missing `target_label` for `action=dropequal`")
+		}
+		if rc.Regex != nil {
+			return nil, fmt.Errorf("`regex` cannot be used for `action=dropequal`")
+		}
 	case "keep":
 		if len(sourceLabels) == 0 && rc.If == nil {
 			return nil, fmt.Errorf("missing `source_labels` for `action=keep`")

lib/promrelabel/config_test.go

@@ -84,7 +84,7 @@ func TestLoadRelabelConfigsSuccess(t *testing.T) {
 	if err != nil {
 		t.Fatalf("cannot load relabel configs from %q: %s", path, err)
 	}
-	nExpected := 16
+	nExpected := 18
 	if n := pcs.Len(); n != nExpected {
 		t.Fatalf("unexpected number of relabel configs loaded from %q; got %d; want %d", path, n, nExpected)
 	}
@@ -266,6 +266,26 @@ func TestParseRelabelConfigsFailure(t *testing.T) {
 			},
 		})
 	})
+	t.Run("keep_if_equal-unused-target-label", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "keep_if_equal",
+				SourceLabels: []string{"foo", "bar"},
+				TargetLabel: "foo",
+			},
+		})
+	})
+	t.Run("keep_if_equal-unused-regex", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "keep_if_equal",
+				SourceLabels: []string{"foo", "bar"},
+				Regex: &MultiLineRegex{
+					S: "bar",
+				},
+			},
+		})
+	})
 	t.Run("drop_if_equal-missing-source-labels", func(t *testing.T) {
 		f([]RelabelConfig{
 			{
@@ -281,6 +301,80 @@ func TestParseRelabelConfigsFailure(t *testing.T) {
 			},
 		})
 	})
+	t.Run("drop_if_equal-unused-target-label", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "drop_if_equal",
+				SourceLabels: []string{"foo", "bar"},
+				TargetLabel: "foo",
+			},
+		})
+	})
+	t.Run("drop_if_equal-unused-regex", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "drop_if_equal",
+				SourceLabels: []string{"foo", "bar"},
+				Regex: &MultiLineRegex{
+					S: "bar",
+				},
+			},
+		})
+	})
+	t.Run("keepequal-missing-source-labels", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "keepequal",
+			},
+		})
+	})
+	t.Run("keepequal-missing-target-label", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "keepequal",
+				SourceLabels: []string{"foo"},
+			},
+		})
+	})
+	t.Run("keepequal-unused-regex", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "keepequal",
+				SourceLabels: []string{"foo"},
+				TargetLabel: "foo",
+				Regex: &MultiLineRegex{
+					S: "bar",
+				},
+			},
+		})
+	})
+	t.Run("dropequal-missing-source-labels", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "dropequal",
+			},
+		})
+	})
+	t.Run("dropequal-missing-target-label", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "dropequal",
+				SourceLabels: []string{"foo"},
+			},
+		})
+	})
+	t.Run("dropequal-unused-regex", func(t *testing.T) {
+		f([]RelabelConfig{
+			{
+				Action: "dropequal",
+				SourceLabels: []string{"foo"},
+				TargetLabel: "foo",
+				Regex: &MultiLineRegex{
+					S: "bar",
+				},
+			},
+		})
+	})
 	t.Run("drop-missing-source-labels", func(t *testing.T) {
 		f([]RelabelConfig{
 			{

lib/promrelabel/relabel.go

@@ -276,6 +276,28 @@ func (prc *parsedRelabelConfig) apply(labels []prompbmarshal.Label, labelsOffset
 			return labels[:labelsOffset]
 		}
 		return labels
+	case "keepequal":
+		// Keep the entry if `source_labels` joined with `separator` matches `target_label`
+		bb := relabelBufPool.Get()
+		bb.B = concatLabelValues(bb.B[:0], src, prc.SourceLabels, prc.Separator)
+		targetValue := getLabelValue(labels[labelsOffset:], prc.TargetLabel)
+		keep := string(bb.B) == targetValue
+		relabelBufPool.Put(bb)
+		if keep {
+			return labels
+		}
+		return labels[:labelsOffset]
+	case "dropequal":
+		// Drop the entry if `source_labels` joined with `separator` doesn't match `target_label`
+		bb := relabelBufPool.Get()
+		bb.B = concatLabelValues(bb.B[:0], src, prc.SourceLabels, prc.Separator)
+		targetValue := getLabelValue(labels[labelsOffset:], prc.TargetLabel)
+		drop := string(bb.B) == targetValue
+		relabelBufPool.Put(bb)
+		if !drop {
+			return labels
+		}
+		return labels[:labelsOffset]
 	case "keep":
 		// Keep the target if `source_labels` joined with `separator` match the `regex`.
 		if prc.RegexAnchored == defaultRegexForRelabelConfig {

lib/promrelabel/relabel_test.go

@@ -399,6 +399,34 @@ func TestParsedRelabelConfigsApply(t *testing.T) {
 - action: drop_if_equal
   source_labels: [xxx, bar]
 `, `{xxx="yyy",bar="yyy"}`, true, `{}`)
+	})
+	t.Run("keepequal-hit", func(t *testing.T) {
+		f(`
+- action: keepequal
+  source_labels: [foo]
+  target_label: bar
+`, `{foo="a",bar="a"}`, true, `{bar="a",foo="a"}`)
+	})
+	t.Run("keepequal-miss", func(t *testing.T) {
+		f(`
+- action: keepequal
+  source_labels: [foo]
+  target_label: bar
+`, `{foo="a",bar="x"}`, true, `{}`)
+	})
+	t.Run("dropequal-hit", func(t *testing.T) {
+		f(`
+- action: dropequal
+  source_labels: [foo]
+  target_label: bar
+`, `{foo="a",bar="a"}`, true, `{}`)
+	})
+	t.Run("dropequal-miss", func(t *testing.T) {
+		f(`
+- action: dropequal
+  source_labels: [foo]
+  target_label: bar
+`, `{foo="a",bar="x"}`, true, `{bar="x",foo="a"}`)
 	})
 	t.Run("keep-miss", func(t *testing.T) {
 		f(`

lib/promrelabel/testdata/relabel_configs_valid.yml

@@ -22,6 +22,12 @@
   source_labels: [foo, bar]
 - action: drop_if_equal
   source_labels: [foo, bar]
+- action: keepequal
+  source_labels: [foo]
+  target_label: bar
+- action: dropequal
+  source_labels: [foo]
+  target_label: bar
 - action: keep
   source_labels: [__name__]
   regex: