Alerting: Add filter and remove funcs for custom labels and annotations (#63437)

This commit adds filterLabels, filterLabelsRe, removeLabels, and
removeLabelsRe functions to templates for custom labels and annotations.
It allows for use cases such as removing all private labels.

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

@@ -4,6 +4,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"net/url"
+	"regexp"
 	"text/template"
 )
 
@@ -14,28 +15,77 @@ type query struct {
 
 var (
 	defaultFuncs = template.FuncMap{
-		"graphLink": graphLink,
-		"tableLink": tableLink,
+		"filterLabels":    filterLabelsFunc,
+		"filterLabelsRe":  filterLabelsReFunc,
+		"graphLink":       graphLinkFunc,
+		"removeLabels":    removeLabelsFunc,
+		"removeLabelslRe": removeLabelsReFunc,
+		"tableLink":       tableLinkFunc,
 	}
 )
 
-var (
-	graphLink = func(data string) string {
-		var q query
-		if err := json.Unmarshal([]byte(data), &q); err != nil {
-			return ""
+// filterLabelsFunc removes all labels that do not match the string.
+func filterLabelsFunc(m Labels, match string) Labels {
+	res := make(Labels)
+	for k, v := range m {
+		if k == match {
+			res[k] = v
 		}
-		datasource := url.QueryEscape(q.Datasource)
-		expr := url.QueryEscape(q.Expr)
-		return fmt.Sprintf(`/explore?left={"datasource":%[1]q,"queries":[{"datasource":%[1]q,"expr":%q,"instant":false,"range":true,"refId":"A"}],"range":{"from":"now-1h","to":"now"}}`, datasource, expr)
 	}
-	tableLink = func(data string) string {
-		var q query
-		if err := json.Unmarshal([]byte(data), &q); err != nil {
-			return ""
+	return res
+}
+
+// filterLabelsReFunc removes all labels that do not match the regex.
+func filterLabelsReFunc(m Labels, pattern string) Labels {
+	re := regexp.MustCompile(pattern)
+	res := make(Labels)
+	for k, v := range m {
+		if re.MatchString(k) {
+			res[k] = v
 		}
-		datasource := url.QueryEscape(q.Datasource)
-		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)
 	}
-)
+	return res
+}
+
+func graphLinkFunc(data string) string {
+	var q query
+	if err := json.Unmarshal([]byte(data), &q); err != nil {
+		return ""
+	}
+	datasource := url.QueryEscape(q.Datasource)
+	expr := url.QueryEscape(q.Expr)
+	return fmt.Sprintf(`/explore?left={"datasource":%[1]q,"queries":[{"datasource":%[1]q,"expr":%q,"instant":false,"range":true,"refId":"A"}],"range":{"from":"now-1h","to":"now"}}`, datasource, expr)
+}
+
+// removeLabelsFunc removes all labels that match the string.
+func removeLabelsFunc(m Labels, match string) Labels {
+	res := make(Labels)
+	for k, v := range m {
+		if k != match {
+			res[k] = v
+		}
+	}
+	return res
+}
+
+// removeLabelsReFunc removes all labels that match the regex.
+func removeLabelsReFunc(m Labels, pattern string) Labels {
+	re := regexp.MustCompile(pattern)
+	res := make(Labels)
+	for k, v := range m {
+		if !re.MatchString(k) {
+			res[k] = v
+		}
+	}
+	return res
+}
+
+func tableLinkFunc(data string) string {
+	var q query
+	if err := json.Unmarshal([]byte(data), &q); err != nil {
+		return ""
+	}
+	datasource := url.QueryEscape(q.Datasource)
+	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)
+}