Add more benchmarks for inhibition rules (#3773)

* Add more benchmarks for inhibition rules

This commit adds more benchmarks for inhibition rules where
just the last rule in the benchmark inhibits the labels.

Signed-off-by: George Robinson <george.robinson@grafana.com>

---------

Signed-off-by: George Robinson <george.robinson@grafana.com>

inhibit/inhibit_bench_test.go

@@ -35,34 +35,46 @@ import (
 // for different numbers of inhibition rules.
 func BenchmarkMutes(b *testing.B) {
 	b.Run("1 inhibition rule, 1 inhibiting alert", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1, 1))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1, 1))
 	})
 	b.Run("10 inhibition rules, 1 inhibiting alert", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 10, 1))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 10, 1))
 	})
 	b.Run("100 inhibition rules, 1 inhibiting alert", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 100, 1))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 100, 1))
 	})
 	b.Run("1000 inhibition rules, 1 inhibiting alert", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1000, 1))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1000, 1))
 	})
 	b.Run("10000 inhibition rules, 1 inhibiting alert", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 10000, 1))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 10000, 1))
 	})
 	b.Run("1 inhibition rule, 10 inhibiting alerts", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1, 10))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1, 10))
 	})
 	b.Run("1 inhibition rule, 100 inhibiting alerts", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1, 100))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1, 100))
 	})
 	b.Run("1 inhibition rule, 1000 inhibiting alerts", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1, 1000))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1, 1000))
 	})
 	b.Run("1 inhibition rule, 10000 inhibiting alerts", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 1, 10000))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 1, 10000))
 	})
 	b.Run("100 inhibition rules, 1000 inhibiting alerts", func(b *testing.B) {
-		benchmarkMutes(b, defaultBenchmark(b, 100, 1000))
+		benchmarkMutes(b, allRulesMatchBenchmark(b, 100, 1000))
+	})
+	b.Run("10 inhibition rules, last rule matches", func(b *testing.B) {
+		benchmarkMutes(b, lastRuleMatchesBenchmark(b, 10))
+	})
+	b.Run("100 inhibition rules, last rule matches", func(b *testing.B) {
+		benchmarkMutes(b, lastRuleMatchesBenchmark(b, 100))
+	})
+	b.Run("1000 inhibition rules, last rule matches", func(b *testing.B) {
+		benchmarkMutes(b, lastRuleMatchesBenchmark(b, 1000))
+	})
+	b.Run("10000 inhibition rules, last rule matches", func(b *testing.B) {
+		benchmarkMutes(b, lastRuleMatchesBenchmark(b, 10000))
 	})
 }
 
@@ -79,19 +91,20 @@ type benchmarkOptions struct {
 	benchFunc func(mutesFunc func(model.LabelSet) bool) error
 }
 
-// defaultBenchmark returns the default benchmark. It supports a number of
-// variations, including customization of the number of inhibition rules,
-// and the number of inhibiting alerts per inhibition rule.
+// allRulesMatchBenchmark returns a new benchmark where all inhibition rules
+// inhibit the label dst=0. It supports a number of variations, including
+// customization of the number of inhibition rules, and the number of
+// inhibiting alerts per inhibition rule.
 //
 // The source matchers are suffixed with the position of the inhibition rule
-// in the list. For example, src=1, src=2, etc. The target matchers are
-// the same across all inhibition rules (dst=0).
+// in the list (e.g. src=1, src=2, etc...). The target matchers are the same
+// across all inhibition rules (dst=0).
 //
 // Each inhibition rule can have zero or more alerts that match the source
 // matchers, and is determined with numInhibitingAlerts.
 //
-// The default benchmark expects dst=0 to be muted and will fail if not.
-func defaultBenchmark(b *testing.B, numInhibitionRules, numInhibitingAlerts int) benchmarkOptions {
+// It expects dst=0 to be muted and will fail if not.
+func allRulesMatchBenchmark(b *testing.B, numInhibitionRules, numInhibitingAlerts int) benchmarkOptions {
 	return benchmarkOptions{
 		n: numInhibitionRules,
 		newRuleFunc: func(idx int) config.InhibitRule {
@@ -126,6 +139,48 @@ func defaultBenchmark(b *testing.B, numInhibitionRules, numInhibitingAlerts int)
 	}
 }
 
+// lastRuleMatchesBenchmark returns a new benchmark where the last inhibition
+// rule inhibits the label dst=0. All other inhibition rules are no-ops.
+//
+// The source matchers are suffixed with the position of the inhibition rule
+// in the list (e.g. src=1, src=2, etc...). The target matchers are the same
+// across all inhibition rules (dst=0).
+//
+// It expects dst=0 to be muted and will fail if not.
+func lastRuleMatchesBenchmark(b *testing.B, n int) benchmarkOptions {
+	return benchmarkOptions{
+		n: n,
+		newRuleFunc: func(idx int) config.InhibitRule {
+			return config.InhibitRule{
+				SourceMatchers: config.Matchers{
+					mustNewMatcher(b, labels.MatchEqual, "src", strconv.Itoa(idx)),
+				},
+				TargetMatchers: config.Matchers{
+					mustNewMatcher(b, labels.MatchEqual, "dst", "0"),
+				},
+			}
+		},
+		newAlertsFunc: func(idx int, _ config.InhibitRule) []types.Alert {
+			// Do not create an alert unless it is the last inhibition rule.
+			if idx < n-1 {
+				return nil
+			}
+			return []types.Alert{{
+				Alert: model.Alert{
+					Labels: model.LabelSet{
+						"src": model.LabelValue(strconv.Itoa(idx)),
+					},
+				},
+			}}
+		}, benchFunc: func(mutesFunc func(set model.LabelSet) bool) error {
+			if ok := mutesFunc(model.LabelSet{"dst": "0"}); !ok {
+				return errors.New("expected dst=0 to be muted")
+			}
+			return nil
+		},
+	}
+}
+
 func benchmarkMutes(b *testing.B, opts benchmarkOptions) {
 	r := prometheus.NewRegistry()
 	m := types.NewMarker(r)
@@ -148,11 +203,7 @@ func benchmarkMutes(b *testing.B, opts benchmarkOptions) {
 	go ih.Run()
 
 	// Wait some time for the inhibitor to seed its cache.
-	waitDuration := time.Millisecond * time.Duration(len(alerts))
-	if waitDuration > time.Second {
-		waitDuration = time.Second
-	}
-	<-time.After(waitDuration)
+	<-time.After(time.Second)
 	b.ResetTimer()
 
 	for i := 0; i < b.N; i++ {