Alerting: Migrate old alerting templates to Go templates (#62911)

* Migrate old alerting templates to use $labels

* Fix imports

* Add test coverage and separate rewriting to Go templates

* Fix lint

* Check for additional closing braces

* Add logging of invalid message templates

* Fix tests

* Small fixes

* Update comments

* Panic on empty token

* Use logtest.Fake

* Fix lint

* Allow for spaces in variable names by not tokenizing spaces

* Add template function to deduplicate Labels in a Value map

* Fix behavior of mapLookupString

* Reference deduplicated labels in migrated message template

* Fix behavior of deduplicateLabelsFunc

* Don't create variable for parent logger

* Add more tests for deduplicateLabelsFunc

* Remove unused function

* Apply suggestions from code review

Co-authored by: Yuri Tseretyan <yuriy.tseretyan@grafana.com>

* Give label val merge function better name

* Extract template migration and escape literal tokens

* Consolidate + simplify template migration

---------

Co-authored-by: William Wernert <william.wernert@grafana.com>

pkg/services/ngalert/state/template/funcs.go

@@ -5,7 +5,10 @@ import (
 	"fmt"
 	"net/url"
 	"regexp"
+	"strings"
 	"text/template"
+
+	"golang.org/x/exp/slices"
 )
 
 type query struct {
@@ -13,14 +16,25 @@ type query struct {
 	Expr       string `json:"expr"`
 }
 
+const (
+	FilterLabelFuncName      = "filterLabels"
+	FilterLabelReFuncName    = "filterLabelsRe"
+	GraphLinkFuncName        = "graphLink"
+	RemoveLabelsFuncName     = "removeLabels"
+	RemoveLabelsReFuncName   = "removeLabelsRe"
+	TableLinkFuncName        = "tableLink"
+	MergeLabelValuesFuncName = "mergeLabelValues"
+)
+
 var (
 	defaultFuncs = template.FuncMap{
-		"filterLabels":    filterLabelsFunc,
-		"filterLabelsRe":  filterLabelsReFunc,
-		"graphLink":       graphLinkFunc,
-		"removeLabels":    removeLabelsFunc,
-		"removeLabelslRe": removeLabelsReFunc,
-		"tableLink":       tableLinkFunc,
+		FilterLabelFuncName:      filterLabelsFunc,
+		FilterLabelReFuncName:    filterLabelsReFunc,
+		GraphLinkFuncName:        graphLinkFunc,
+		RemoveLabelsFuncName:     removeLabelsFunc,
+		RemoveLabelsReFuncName:   removeLabelsReFunc,
+		TableLinkFuncName:        tableLinkFunc,
+		MergeLabelValuesFuncName: mergeLabelValuesFunc,
 	}
 )
 
@@ -89,3 +103,32 @@ func tableLinkFunc(data string) string {
 	expr := url.QueryEscape(q.Expr)
 	return fmt.Sprintf(`/explore?left={"datasource":%[1]q,"queries":[{"datasource":%[1]q,"expr":%q,"instant":true,"range":false,"refId":"A"}],"range":{"from":"now-1h","to":"now"}}`, datasource, expr)
 }
+
+// mergeLabelValuesFunc returns a map of label keys to deduplicated and comma separated values.
+func mergeLabelValuesFunc(values map[string]Value) Labels {
+	type uniqueLabelVals map[string]struct{}
+
+	labels := make(map[string]uniqueLabelVals)
+	for _, value := range values {
+		for k, v := range value.Labels {
+			var ul uniqueLabelVals
+			var ok bool
+			if ul, ok = labels[k]; !ok {
+				ul = uniqueLabelVals{}
+				labels[k] = ul
+			}
+			ul[v] = struct{}{}
+		}
+	}
+
+	res := make(Labels)
+	for label, vals := range labels {
+		keys := make([]string, 0, len(vals))
+		for val := range vals {
+			keys = append(keys, val)
+		}
+		slices.Sort(keys)
+		res[label] = strings.Join(keys, ", ")
+	}
+	return res
+}

pkg/services/ngalert/state/template/funcs_test.go

@@ -25,3 +25,27 @@ func TestRemoveLabelsReFunc(t *testing.T) {
 	l := Labels{"foo": "bar", "bar": "baz"}
 	assert.Equal(t, Labels{"bar": "baz"}, removeLabelsReFunc(l, "f.*"))
 }
+
+func TestDeduplicateLabelsFunc(t *testing.T) {
+	v := map[string]Value{
+		"v1": {Labels: Labels{"foo": "bar", "bar": "foo"}, Value: 1},
+		"v2": {Labels: Labels{"foo": "bar", "bar": "baz", "baz": "bat"}, Value: 2},
+	}
+	assert.Equal(t, Labels{"foo": "bar", "bar": "baz, foo", "baz": "bat"}, mergeLabelValuesFunc(v))
+}
+
+func TestDeduplicateLabelsFuncAllSameVal(t *testing.T) {
+	v := map[string]Value{
+		"v1": {Labels: Labels{"foo": "bar", "bar": "baz"}, Value: 1},
+		"v2": {Labels: Labels{"foo": "bar", "bar": "baz"}, Value: 2},
+	}
+	assert.Equal(t, Labels{"foo": "bar", "bar": "baz"}, mergeLabelValuesFunc(v))
+}
+
+func TestDeduplicateLabelsFuncNoDuplicates(t *testing.T) {
+	v := map[string]Value{
+		"v1": {Labels: Labels{"foo": "bar"}, Value: 1},
+		"v2": {Labels: Labels{"bar": "baz"}, Value: 2},
+	}
+	assert.Equal(t, Labels{"foo": "bar", "bar": "baz"}, mergeLabelValuesFunc(v))
+}