Allow rules to be loaded to rulers as backup for List rules API HA

Signed-off-by: Emmanuel Lodovice <[email protected]>

Author: emanlodovice

CHANGELOG.md

@@ -14,6 +14,7 @@
 * [FEATURE] Ruler: Add `ruler.concurrent-evals-enabled` flag to enable concurrent evaluation within a single rule group for independent rules. Maximum concurrency can be configured via `ruler.max-concurrent-evals`. #5766
 * [FEATURE] Distributor Queryable: Experimental: Add config `zone_results_quorum_metadata`. When querying ingesters using metadata APIs such as label names and values, only results from quorum number of zones will be included and merged. #5779
 * [FEATURE] Storage Cache Clients: Add config `set_async_circuit_breaker_config` to utilize the circuit breaker pattern for dynamically thresholding asynchronous set operations. Implemented in both memcached and redis cache clients. #5789
+* [FEATURE] Ruler: Add `ruler.api-deduplicate-rules` flag to remove duplicate rule groups from the Prometheus compatible rules API endpoint. Add `ruler.ring.replication-factor` and `ruler.ring.zone-awareness-enabled` flags to configure rule group replication, but only the first ruler in the replicaset evaluates the rule group, the rest will just hold a copy as backup. Add `ruler.api-enable-rules-backup` flag to configure rulers to send the rule group backups stored in the replicaset to handle events when a ruler is down during an API request to list rules. #5782
 * [ENHANCEMENT] Store Gateway: Added `-store-gateway.enabled-tenants` and `-store-gateway.disabled-tenants` to explicitly enable or disable store-gateway for specific tenants. #5638
 * [ENHANCEMENT] Compactor: Add new compactor metric `cortex_compactor_start_duration_seconds`. #5683
 * [ENHANCEMENT] Upgraded Docker base images to `alpine:3.18`. #5684

docs/configuration/config-file-reference.md

@@ -4254,6 +4254,21 @@ ring:
 # CLI flag: -experimental.ruler.enable-api
 [enable_api: <boolean> | default = false]
 
+# Enable rulers to store a copy of rules owned by other rulers with default
+# state (state before any evaluation) and send this copy in list API requests as
+# backup in case the ruler who owns the rule fails to send its rules. This
+# allows the rules API to handle ruler outage by returning rules with default
+# state. Ring replication-factor needs to be set to 3 or more for this to be
+# useful.
+# CLI flag: -ruler.api-enable-rules-backup
+[api_enable_rules_backup: <boolean> | default = false]
+
+# Remove duplicate rules in the prometheus rules and alerts API response. If
+# there are duplicate rules the rule with the latest evaluation timestamp will
+# be kept.
+# CLI flag: -ruler.api-deduplicate-rules
+[api_deduplicate_rules: <boolean> | default = false]
+
 # Comma separated list of tenants whose rules this ruler can evaluate. If
 # specified, only these tenants will be handled by ruler, otherwise this ruler
 # can process rules from all tenants. Subject to sharding.

pkg/ruler/api.go

@@ -251,6 +251,9 @@ func (a *API) PrometheusRules(w http.ResponseWriter, req *http.Request) {
 
 	// keep data.groups are in order
 	sort.Slice(groups, func(i, j int) bool {
+		if groups[i].File == groups[j].File {
+			return groups[i].Name < groups[j].Name
+		}
 		return groups[i].File < groups[j].File
 	})
 

pkg/ruler/manager.go

@@ -44,6 +44,9 @@ type DefaultMultiTenantManager struct {
 	notifiers                 map[string]*rulerNotifier
 	notifiersDiscoveryMetrics map[string]discovery.DiscovererMetrics
 
+	// rules backup
+	rulesBackupManager *rulesBackupManager
+
 	managersTotal                 prometheus.Gauge
 	lastReloadSuccessful          *prometheus.GaugeVec
 	lastReloadSuccessfulTimestamp *prometheus.GaugeVec
@@ -85,6 +88,7 @@ func NewDefaultMultiTenantManager(cfg Config, managerFactory ManagerFactory, eva
 		mapper:                    newMapper(cfg.RulePath, logger),
 		userManagers:              map[string]RulesManager{},
 		userManagerMetrics:        userManagerMetrics,
+		rulesBackupManager:        newRulesBackupManager(cfg, logger, reg),
 		managersTotal: promauto.With(reg).NewGauge(prometheus.GaugeOpts{
 			Namespace: "cortex",
 			Name:      "ruler_managers_total",
@@ -142,8 +146,12 @@ func (r *DefaultMultiTenantManager) SyncRuleGroups(ctx context.Context, ruleGrou
 	r.managersTotal.Set(float64(len(r.userManagers)))
 }
 
+func (r *DefaultMultiTenantManager) BackUpRuleGroups(ctx context.Context, ruleGroups map[string]rulespb.RuleGroupList) {
+	r.rulesBackupManager.backUpRuleGroups(ctx, ruleGroups)
+}
+
 // syncRulesToManager maps the rule files to disk, detects any changes and will create/update the
-// the users Prometheus Rules Manager.
+// users Prometheus Rules Manager.
 func (r *DefaultMultiTenantManager) syncRulesToManager(ctx context.Context, user string, groups rulespb.RuleGroupList) {
 	// Map the files to disk and return the file names to be passed to the users manager if they
 	// have been updated
@@ -279,6 +287,10 @@ func (r *DefaultMultiTenantManager) GetRules(userID string) []*promRules.Group {
 	return groups
 }
 
+func (r *DefaultMultiTenantManager) GetBackupRules(userID string) []*promRules.Group {
+	return r.rulesBackupManager.getRuleGroups(userID)
+}
+
 func (r *DefaultMultiTenantManager) Stop() {
 	r.notifiersMtx.Lock()
 	for _, n := range r.notifiers {

pkg/ruler/manager_test.go

@@ -138,6 +138,55 @@ func TestSyncRuleGroupsCleanUpPerUserMetrics(t *testing.T) {
 	require.NotContains(t, mfm["cortex_ruler_config_last_reload_successful"].String(), "value:\""+user+"\"")
 }
 
+func TestBackupRules(t *testing.T) {
+	dir := t.TempDir()
+	reg := prometheus.NewPedanticRegistry()
+	evalMetrics := NewRuleEvalMetrics(Config{RulePath: dir, EnableQueryStats: true}, reg)
+	m, err := NewDefaultMultiTenantManager(Config{RulePath: dir}, factory, evalMetrics, reg, log.NewNopLogger())
+	require.NoError(t, err)
+
+	const user1 = "testUser"
+	const user2 = "testUser2"
+
+	require.Equal(t, 0, len(m.GetBackupRules(user1)))
+	require.Equal(t, 0, len(m.GetBackupRules(user2)))
+
+	userRules := map[string]rulespb.RuleGroupList{
+		user1: {
+			&rulespb.RuleGroupDesc{
+				Name:      "group1",
+				Namespace: "ns",
+				Interval:  1 * time.Minute,
+				User:      user1,
+			},
+		},
+		user2: {
+			&rulespb.RuleGroupDesc{
+				Name:      "group2",
+				Namespace: "ns",
+				Interval:  1 * time.Minute,
+				User:      user1,
+			},
+		},
+	}
+	m.BackUpRuleGroups(context.TODO(), userRules)
+	managerOptions := &promRules.ManagerOptions{}
+	g1 := promRules.NewGroup(promRules.GroupOptions{
+		Name:     userRules[user1][0].Name,
+		File:     userRules[user1][0].Namespace,
+		Interval: userRules[user1][0].Interval,
+		Opts:     managerOptions,
+	})
+	g2 := promRules.NewGroup(promRules.GroupOptions{
+		Name:     userRules[user2][0].Name,
+		File:     userRules[user2][0].Namespace,
+		Interval: userRules[user2][0].Interval,
+		Opts:     managerOptions,
+	})
+	requireGroupsEqual(t, m.GetBackupRules(user1), []*promRules.Group{g1})
+	requireGroupsEqual(t, m.GetBackupRules(user2), []*promRules.Group{g2})
+}
+
 func getManager(m *DefaultMultiTenantManager, user string) RulesManager {
 	m.userManagerMtx.Lock()
 	defer m.userManagerMtx.Unlock()

pkg/ruler/merger.go

@@ -0,0 +1,34 @@
+package ruler
+
+import (
+	"time"
+
+	promRules "github.com/prometheus/prometheus/rules"
+)
+
+// mergeGroupStateDesc removes duplicates from the provided []*GroupStateDesc by keeping the GroupStateDesc with the
+// latest information. It uses the EvaluationTimestamp of the GroupStateDesc and the EvaluationTimestamp of the
+// ActiveRules in a GroupStateDesc to determine the which GroupStateDesc has the latest information.
+func mergeGroupStateDesc(in []*GroupStateDesc) []*GroupStateDesc {
+	states := make(map[string]*GroupStateDesc)
+	rgTime := make(map[string]time.Time)
+	for _, state := range in {
+		latestTs := state.EvaluationTimestamp
+		for _, r := range state.ActiveRules {
+			if latestTs.Before(r.EvaluationTimestamp) {
+				latestTs = r.EvaluationTimestamp
+			}
+		}
+		key := promRules.GroupKey(state.Group.Namespace, state.Group.Name)
+		ts, ok := rgTime[key]
+		if !ok || ts.Before(latestTs) {
+			states[key] = state
+			rgTime[key] = latestTs
+		}
+	}
+	groups := make([]*GroupStateDesc, 0, len(states))
+	for _, state := range states {
+		groups = append(groups, state)
+	}
+	return groups
+}

pkg/ruler/merger_test.go

@@ -0,0 +1,114 @@
+package ruler
+
+import (
+	"reflect"
+	"slices"
+	"strings"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/require"
+
+	"github.com/cortexproject/cortex/pkg/ruler/rulespb"
+)
+
+func TestMergeGroupStateDesc(t *testing.T) {
+	curTime := time.Now()
+	r := rulespb.RuleDesc{
+		Expr: "1 > 1",
+	}
+	g1 := rulespb.RuleGroupDesc{
+		Name:      "g1",
+		Namespace: "ns1",
+	}
+	g2 := rulespb.RuleGroupDesc{
+		Name:      "g2",
+		Namespace: "ns1",
+	}
+	rs1 := RuleStateDesc{
+		Rule:                &r,
+		EvaluationTimestamp: curTime,
+	}
+	rs1NotRun := RuleStateDesc{
+		Rule: &r,
+	}
+	rs2 := RuleStateDesc{
+		Rule:                &r,
+		EvaluationTimestamp: curTime,
+	}
+	rs2NotRun := RuleStateDesc{
+		Rule: &r,
+	}
+	rs3 := RuleStateDesc{
+		Rule:                &r,
+		EvaluationTimestamp: curTime.Add(10 * time.Second),
+	}
+
+	gs1 := GroupStateDesc{
+		Group:               &g1,
+		ActiveRules:         []*RuleStateDesc{&rs1, &rs2},
+		EvaluationTimestamp: curTime,
+	}
+	gs1NotRun := GroupStateDesc{
+		Group:       &g1,
+		ActiveRules: []*RuleStateDesc{&rs1NotRun, &rs2NotRun},
+	}
+	gs2 := GroupStateDesc{
+		Group:               &g2,
+		ActiveRules:         []*RuleStateDesc{&rs1, &rs2},
+		EvaluationTimestamp: curTime,
+	}
+	gs2NotRun := GroupStateDesc{
+		Group:       &g2,
+		ActiveRules: []*RuleStateDesc{&rs1NotRun, &rs2NotRun},
+	}
+	gs3 := GroupStateDesc{
+		Group:               &g2,
+		ActiveRules:         []*RuleStateDesc{&rs1, &rs3},
+		EvaluationTimestamp: curTime,
+	}
+
+	type testCase struct {
+		input          []*GroupStateDesc
+		expectedOutput []*GroupStateDesc
+	}
+
+	testCases := map[string]testCase{
+		"No duplicate": {
+			input:          []*GroupStateDesc{&gs1, &gs2},
+			expectedOutput: []*GroupStateDesc{&gs1, &gs2},
+		},
+		"No duplicate but not evaluated": {
+			input:          []*GroupStateDesc{&gs1NotRun, &gs2NotRun},
+			expectedOutput: []*GroupStateDesc{&gs1NotRun, &gs2NotRun},
+		},
+		"With exact duplicate": {
+			input:          []*GroupStateDesc{&gs1, &gs2NotRun, &gs1, &gs2NotRun},
+			expectedOutput: []*GroupStateDesc{&gs1, &gs2NotRun},
+		},
+		"With duplicates that are not evaluated": {
+			input:          []*GroupStateDesc{&gs1, &gs2, &gs1NotRun, &gs2NotRun},
+			expectedOutput: []*GroupStateDesc{&gs1, &gs2},
+		},
+		"With duplicate with a new newer rule evaluation": {
+			input:          []*GroupStateDesc{&gs3, &gs1, &gs2, &gs1NotRun},
+			expectedOutput: []*GroupStateDesc{&gs1, &gs3},
+		},
+	}
+
+	for name, tc := range testCases {
+		t.Run(name, func(t *testing.T) {
+			out := mergeGroupStateDesc(tc.input)
+			slices.SortFunc(out, func(a, b *GroupStateDesc) int {
+				fileCompare := strings.Compare(a.Group.Namespace, b.Group.Namespace)
+				if fileCompare != 0 {
+					return fileCompare
+				}
+				return strings.Compare(a.Group.Name, b.Group.Name)
+			})
+			require.Equal(t, len(tc.expectedOutput), len(out))
+			require.True(t, reflect.DeepEqual(tc.expectedOutput, out))
+		})
+	}
+
+}