From 44f385fd519197f8b93075fc5ec795818f5fdb74 Mon Sep 17 00:00:00 2001
From: suntala <arati.rana@grafana.com>
Date: Tue, 12 Mar 2024 20:14:31 +0100
Subject: [PATCH] Support expansion of native histogram values in alert
 templates

Co-authored-by: Aleks Fazlieva <britishrum@users.noreply.github.com>
Signed-off-by: suntala <arati.rana@grafana.com>
---
 model/rulefmt/rulefmt.go |  3 +-
 rules/alerting.go        |  2 +-
 rules/alerting_test.go   | 62 ++++++++++++++++++++++++++++++++++++++++
 template/template.go     | 14 ++++++---
 4 files changed, 75 insertions(+), 6 deletions(-)

diff --git a/model/rulefmt/rulefmt.go b/model/rulefmt/rulefmt.go
index 03cbd8849..4ed1619d6 100644
--- a/model/rulefmt/rulefmt.go
+++ b/model/rulefmt/rulefmt.go
@@ -27,6 +27,7 @@ import (
 	"gopkg.in/yaml.v3"
 
 	"github.com/prometheus/prometheus/model/timestamp"
+	"github.com/prometheus/prometheus/promql"
 	"github.com/prometheus/prometheus/promql/parser"
 	"github.com/prometheus/prometheus/template"
 )
@@ -256,7 +257,7 @@ func testTemplateParsing(rl *RuleNode) (errs []error) {
 	}
 
 	// Trying to parse templates.
-	tmplData := template.AlertTemplateData(map[string]string{}, map[string]string{}, "", 0)
+	tmplData := template.AlertTemplateData(map[string]string{}, map[string]string{}, "", promql.Sample{})
 	defs := []string{
 		"{{$labels := .Labels}}",
 		"{{$externalLabels := .ExternalLabels}}",
diff --git a/rules/alerting.go b/rules/alerting.go
index 7b0921a72..50c67fa2d 100644
--- a/rules/alerting.go
+++ b/rules/alerting.go
@@ -364,7 +364,7 @@ func (r *AlertingRule) Eval(ctx context.Context, ts time.Time, query QueryFunc,
 		// Provide the alert information to the template.
 		l := smpl.Metric.Map()
 
-		tmplData := template.AlertTemplateData(l, r.externalLabels, r.externalURL, smpl.F)
+		tmplData := template.AlertTemplateData(l, r.externalLabels, r.externalURL, smpl)
 		// Inject some convenience variables that are easier to remember for users
 		// who are not used to Go's templating system.
 		defs := []string{
diff --git a/rules/alerting_test.go b/rules/alerting_test.go
index a270731d9..ddfe345ef 100644
--- a/rules/alerting_test.go
+++ b/rules/alerting_test.go
@@ -23,6 +23,7 @@ import (
 	"github.com/prometheus/common/model"
 	"github.com/stretchr/testify/require"
 
+	"github.com/prometheus/prometheus/model/histogram"
 	"github.com/prometheus/prometheus/model/labels"
 	"github.com/prometheus/prometheus/model/relabel"
 	"github.com/prometheus/prometheus/model/timestamp"
@@ -85,6 +86,67 @@ func TestAlertingRuleState(t *testing.T) {
 	}
 }
 
+func TestAlertingRuleTemplateWithHistogram(t *testing.T) {
+	h := histogram.FloatHistogram{
+		Schema:        0,
+		Count:         30,
+		Sum:           1111.1,
+		ZeroThreshold: 0.001,
+		ZeroCount:     2,
+		PositiveSpans: []histogram.Span{
+			{Offset: 0, Length: 1},
+			{Offset: 1, Length: 5},
+		},
+		PositiveBuckets: []float64{1, 1, 2, 1, 1, 1},
+		NegativeSpans: []histogram.Span{
+			{Offset: 1, Length: 4},
+			{Offset: 4, Length: 3},
+		},
+		NegativeBuckets: []float64{-2, 2, 2, 7, 5, 5, 2},
+	}
+
+	q := func(ctx context.Context, qs string, t time.Time) (promql.Vector, error) {
+		return []promql.Sample{{H: &h}}, nil
+	}
+
+	expr, err := parser.ParseExpr("foo")
+	require.NoError(t, err)
+
+	rule := NewAlertingRule(
+		"HistogramAsValue",
+		expr,
+		time.Minute,
+		0,
+		labels.FromStrings("histogram", "{{ $value }}"),
+		labels.EmptyLabels(), labels.EmptyLabels(), "", true, nil,
+	)
+
+	evalTime := time.Now()
+	res, err := rule.Eval(context.TODO(), evalTime, q, nil, 0)
+	require.NoError(t, err)
+
+	require.Len(t, res, 2)
+	for _, smpl := range res {
+		smplName := smpl.Metric.Get("__name__")
+		if smplName == "ALERTS" {
+			result := promql.Sample{
+				Metric: labels.FromStrings(
+					"__name__", "ALERTS",
+					"alertname", "HistogramAsValue",
+					"alertstate", "pending",
+					"histogram", h.String(),
+				),
+				T: timestamp.FromTime(evalTime),
+				F: 1,
+			}
+			testutil.RequireEqual(t, result, smpl)
+		} else {
+			// If not 'ALERTS', it has to be 'ALERTS_FOR_STATE'.
+			require.Equal(t, "ALERTS_FOR_STATE", smplName)
+		}
+	}
+}
+
 func TestAlertingRuleLabelsUpdate(t *testing.T) {
 	storage := promql.LoadedStorage(t, `
 		load 1m
diff --git a/template/template.go b/template/template.go
index 5d72a7e83..f04f5ea53 100644
--- a/template/template.go
+++ b/template/template.go
@@ -355,18 +355,24 @@ func NewTemplateExpander(
 }
 
 // AlertTemplateData returns the interface to be used in expanding the template.
-func AlertTemplateData(labels, externalLabels map[string]string, externalURL string, value float64) interface{} {
-	return struct {
+func AlertTemplateData(labels, externalLabels map[string]string, externalURL string, smpl promql.Sample) interface{} {
+	res := struct {
 		Labels         map[string]string
 		ExternalLabels map[string]string
 		ExternalURL    string
-		Value          float64
+		Value          interface{}
 	}{
 		Labels:         labels,
 		ExternalLabels: externalLabels,
 		ExternalURL:    externalURL,
-		Value:          value,
+		Value:          smpl.F,
 	}
+
+	if smpl.H != nil {
+		res.Value = smpl.H
+	}
+
+	return res
 }
 
 // Funcs adds the functions in fm to the Expander's function map.