From f3394bf7a1f362b88d89cb0784be47b75d8fa152 Mon Sep 17 00:00:00 2001
From: gotjosh <josue.abreu@gmail.com>
Date: Tue, 18 Apr 2023 10:07:32 +0100
Subject: [PATCH] Rules API: Allow filtering by rule name

Introduces support for a new query parameter in the `/rules` API endpoint that allows filtering by rule names.

If all the rules of a group are filtered, we skip the group entirely.

Signed-off-by: gotjosh <josue.abreu@gmail.com>
---
 docs/querying/api.md   |  2 ++
 web/api/v1/api.go      | 33 +++++++++++++++++++++++++++------
 web/api/v1/api_test.go | 27 +++++++++++++++++++++++++++
 3 files changed, 56 insertions(+), 6 deletions(-)

diff --git a/docs/querying/api.md b/docs/querying/api.md
index f2182a205..0cc549b65 100644
--- a/docs/querying/api.md
+++ b/docs/querying/api.md
@@ -673,7 +673,9 @@ GET /api/v1/rules
 ```
 
 URL query parameters:
+
 - `type=alert|record`: return only the alerting rules (e.g. `type=alert`) or the recording rules (e.g. `type=record`). When the parameter is absent or empty, no filtering is done.
+- `rules=alertName,RuleName`: return only the alerting and recording rules with the specified names. If we've filtered out all the rules of a group, the group is not returned. When the parameter is absent or empty, no filtering is done.
 
 ```json
 $ curl http://localhost:9090/api/v1/rules
diff --git a/web/api/v1/api.go b/web/api/v1/api.go
index aeea87ca7..d95595804 100644
--- a/web/api/v1/api.go
+++ b/web/api/v1/api.go
@@ -1296,6 +1296,16 @@ func (api *API) rules(r *http.Request) apiFuncResult {
 	res := &RuleDiscovery{RuleGroups: make([]*RuleGroup, len(ruleGroups))}
 	typ := strings.ToLower(r.URL.Query().Get("type"))
 
+	// Parse the rule names into a comma separated list of rule names, then create a set.
+	rulesQuery := r.URL.Query().Get("rules")
+	ruleNamesSet := map[string]struct{}{}
+	if rulesQuery != "" {
+		names := strings.Split(rulesQuery, ",")
+		for _, rn := range names {
+			ruleNamesSet[strings.TrimSpace(rn)] = struct{}{}
+		}
+	}
+
 	if typ != "" && typ != "alert" && typ != "record" {
 		return invalidParamError(errors.Errorf("not supported value %q", typ), "type")
 	}
@@ -1313,14 +1323,20 @@ func (api *API) rules(r *http.Request) apiFuncResult {
 			EvaluationTime: grp.GetEvaluationTime().Seconds(),
 			LastEvaluation: grp.GetLastEvaluation(),
 		}
-		for _, r := range grp.Rules() {
+		for _, rr := range grp.Rules() {
 			var enrichedRule Rule
 
-			lastError := ""
-			if r.LastError() != nil {
-				lastError = r.LastError().Error()
+			if len(ruleNamesSet) > 0 {
+				if _, ok := ruleNamesSet[rr.Name()]; !ok {
+					continue
+				}
 			}
-			switch rule := r.(type) {
+
+			lastError := ""
+			if rr.LastError() != nil {
+				lastError = rr.LastError().Error()
+			}
+			switch rule := rr.(type) {
 			case *rules.AlertingRule:
 				if !returnAlerts {
 					break
@@ -1358,11 +1374,16 @@ func (api *API) rules(r *http.Request) apiFuncResult {
 				err := errors.Errorf("failed to assert type of rule '%v'", rule.Name())
 				return apiFuncResult{nil, &apiError{errorInternal, err}, nil, nil}
 			}
+
 			if enrichedRule != nil {
 				apiRuleGroup.Rules = append(apiRuleGroup.Rules, enrichedRule)
 			}
 		}
-		res.RuleGroups[i] = apiRuleGroup
+
+		// If the rule group response has no rules, skip it - this means we filtered all the rules of this group.
+		if len(apiRuleGroup.Rules) > 0 {
+			res.RuleGroups[i] = apiRuleGroup
+		}
 	}
 	return apiFuncResult{res, nil, nil, nil}
 }
diff --git a/web/api/v1/api_test.go b/web/api/v1/api_test.go
index efce04221..e354bf298 100644
--- a/web/api/v1/api_test.go
+++ b/web/api/v1/api_test.go
@@ -1973,6 +1973,33 @@ func testEndpoints(t *testing.T, api *API, tr *testTargetRetriever, es storage.E
 				},
 			},
 		},
+		{
+			endpoint: api.rules,
+			query:    url.Values{"rules": []string{"test_metric4"}},
+			response: &RuleDiscovery{
+				RuleGroups: []*RuleGroup{
+					{
+						Name:     "grp",
+						File:     "/path/to/file",
+						Interval: 1,
+						Limit:    0,
+						Rules: []Rule{
+							AlertingRule{
+								State:       "inactive",
+								Name:        "test_metric4",
+								Query:       "up == 1",
+								Duration:    1,
+								Labels:      labels.Labels{},
+								Annotations: labels.Labels{},
+								Alerts:      []*Alert{},
+								Health:      "unknown",
+								Type:        "alerting",
+							},
+						},
+					},
+				},
+			},
+		},
 		{
 			endpoint: api.queryExemplars,
 			query: url.Values{