From 13854b6f2274a901e7b4fa0aa3bbecd09ba0bb9a Mon Sep 17 00:00:00 2001
From: Arve Knudsen <arve.knudsen@gmail.com>
Date: Tue, 13 Sep 2022 09:35:03 +0200
Subject: [PATCH] rules: Add parameter controlling the max number of alerts
 rules can generate

Rule group parameter alert_limit controls the maximum number of alerts
rules belonging to the group can generate. It's similar to the existing
limit parameter, but doesn't affect recording rules.

Signed-off-by: Arve Knudsen <arve.knudsen@gmail.com>
---
 model/rulefmt/rulefmt.go |  1 +
 rules/manager.go         | 19 ++++++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/model/rulefmt/rulefmt.go b/model/rulefmt/rulefmt.go
index 7cfb2e9d18..5fdaacdddf 100644
--- a/model/rulefmt/rulefmt.go
+++ b/model/rulefmt/rulefmt.go
@@ -139,6 +139,7 @@ type RuleGroup struct {
 	Interval        model.Duration  `yaml:"interval,omitempty"`
 	EvaluationDelay *model.Duration `yaml:"evaluation_delay,omitempty"`
 	Limit           int             `yaml:"limit,omitempty"`
+	AlertLimit      int             `yaml:"alert_limit,omitempty"`
 	Rules           []RuleNode      `yaml:"rules"`
 	SourceTenants   []string        `yaml:"source_tenants,omitempty"`
 }
diff --git a/rules/manager.go b/rules/manager.go
index 2fe65eb21c..22dc34b1ae 100644
--- a/rules/manager.go
+++ b/rules/manager.go
@@ -246,6 +246,7 @@ type Group struct {
 	interval             time.Duration
 	evaluationDelay      *time.Duration
 	limit                int
+	alertLimit           int
 	rules                []Rule
 	sourceTenants        []string
 	seriesInPreviousEval []map[string]labels.Labels // One per Rule.
@@ -277,6 +278,7 @@ type GroupOptions struct {
 	Name, File               string
 	Interval                 time.Duration
 	Limit                    int
+	AlertLimit               int
 	Rules                    []Rule
 	SourceTenants            []string
 	ShouldRestore            bool
@@ -310,6 +312,7 @@ func NewGroup(o GroupOptions) *Group {
 		interval:                 o.Interval,
 		evaluationDelay:          o.EvaluationDelay,
 		limit:                    o.Limit,
+		alertLimit:               o.AlertLimit,
 		rules:                    o.Rules,
 		shouldRestore:            o.ShouldRestore,
 		opts:                     o.Opts,
@@ -345,6 +348,9 @@ func (g *Group) Interval() time.Duration { return g.interval }
 // Limit returns the group's limit.
 func (g *Group) Limit() int { return g.limit }
 
+// AlertLimit returns the group's alert limit.
+func (g *Group) AlertLimit() int { return g.alertLimit }
+
 // SourceTenants returns the source tenants for the group.
 // If it's empty or nil, then the owning user/tenant is considered to be the source tenant.
 func (g *Group) SourceTenants() []string { return g.sourceTenants }
@@ -634,7 +640,13 @@ func (g *Group) Eval(ctx context.Context, ts time.Time) {
 
 			g.metrics.EvalTotal.WithLabelValues(GroupKey(g.File(), g.Name())).Inc()
 
-			vector, err := rule.Eval(ctx, evaluationDelay, ts, g.opts.QueryFunc, g.opts.ExternalURL, g.Limit())
+			limit := g.Limit()
+			if _, ok := rule.(*AlertingRule); ok {
+				if g.AlertLimit() > 0 {
+					limit = g.AlertLimit()
+				}
+			}
+			vector, err := rule.Eval(ctx, evaluationDelay, ts, g.opts.QueryFunc, g.opts.ExternalURL, limit)
 			if err != nil {
 				rule.SetHealth(HealthBad)
 				rule.SetLastError(err)
@@ -891,6 +903,10 @@ func (g *Group) Equals(ng *Group) bool {
 		return false
 	}
 
+	if g.alertLimit != ng.alertLimit {
+		return false
+	}
+
 	if len(g.rules) != len(ng.rules) {
 		return false
 	}
@@ -1163,6 +1179,7 @@ func (m *Manager) LoadGroups(
 				File:                     fn,
 				Interval:                 itv,
 				Limit:                    rg.Limit,
+				AlertLimit:               rg.AlertLimit,
 				Rules:                    rules,
 				SourceTenants:            rg.SourceTenants,
 				ShouldRestore:            shouldRestore,