Unify direct and caching RuleStores in ruler (#9434)

Instead of using two different `RuleStore` implementations within the Ruler,
use a single caching implementation and selectively disable caching when
required.

This change removes the "direct" `RuleStore` implementation from the Ruler's
gRPC and HTTP API layers. Instead, the caching implementation is used for all
calls. In cases where caching returning stale results would not be acceptable,
the caching is disabled _just_ for that call.

This allows rule group contents to be safety cached with the understanding
that it is safe to cache them because they will correctly invalidated when
deleted or modified.

Part of #9386

Signed-off-by: Nick Pillitteri <nick.pillitteri@grafana.com>

Author: 56quarters

development/mimir-microservices-mode/docker-compose.jsonnet

@@ -294,7 +294,7 @@ std.manifestYamlDoc({
 
   memcached:: {
     memcached: {
-      image: 'memcached:1.6.19-alpine',
+      image: 'memcached:1.6.28-alpine',
       ports: [
         '11211:11211',
       ],
@@ -303,7 +303,7 @@ std.manifestYamlDoc({
 
   memcached_exporter:: {
     'memcached-exporter': {
-      image: 'prom/memcached-exporter:v0.6.0',
+      image: 'prom/memcached-exporter:v0.14.4',
       command: ['--memcached.address=memcached:11211', '--web.listen-address=0.0.0.0:9150'],
     },
   },

development/mimir-microservices-mode/docker-compose.yml

@@ -275,14 +275,14 @@
     "ports":
       - "9900:9900"
   "memcached":
-    "image": "memcached:1.6.19-alpine"
+    "image": "memcached:1.6.28-alpine"
     "ports":
       - "11211:11211"
   "memcached-exporter":
     "command":
       - "--memcached.address=memcached:11211"
       - "--web.listen-address=0.0.0.0:9150"
-    "image": "prom/memcached-exporter:v0.6.0"
+    "image": "prom/memcached-exporter:v0.14.4"
   "minio":
     "command":
       - "server"

pkg/mimir/mimir.go

@@ -723,8 +723,7 @@ type Mimir struct {
 	QueryFrontendTopicOffsetsReader *ingest.TopicOffsetsReader
 	QueryFrontendCodec              querymiddleware.Codec
 	Ruler                           *ruler.Ruler
-	RulerDirectStorage              rulestore.RuleStore
-	RulerCachedStorage              rulestore.RuleStore
+	RulerStorage                    rulestore.RuleStore
 	Alertmanager                    *alertmanager.MultitenantAlertmanager
 	Compactor                       *compactor.MultitenantCompactor
 	StoreGateway                    *storegateway.StoreGateway

pkg/mimir/modules.go

@@ -830,13 +830,12 @@ func (t *Mimir) initRulerStorage() (serv services.Service, err error) {
 	// we do accept stale data for about a polling interval (2 intervals in the worst
 	// case scenario due to the jitter applied).
 	cacheTTL := t.Cfg.Ruler.PollInterval
-
-	t.RulerDirectStorage, t.RulerCachedStorage, err = ruler.NewRuleStore(context.Background(), t.Cfg.RulerStorage, t.Overrides, rules.FileLoader{}, cacheTTL, util_log.Logger, t.Registerer)
+	t.RulerStorage, err = ruler.NewRuleStore(context.Background(), t.Cfg.RulerStorage, t.Overrides, rules.FileLoader{}, cacheTTL, util_log.Logger, t.Registerer)
 	return
 }
 
 func (t *Mimir) initRuler() (serv services.Service, err error) {
-	if t.RulerDirectStorage == nil {
+	if t.RulerStorage == nil {
 		level.Info(util_log.Logger).Log("msg", "The ruler storage has not been configured. Not starting the ruler.")
 		return nil, nil
 	}
@@ -939,8 +938,7 @@ func (t *Mimir) initRuler() (serv services.Service, err error) {
 		manager,
 		t.Registerer,
 		util_log.Logger,
-		t.RulerDirectStorage,
-		t.RulerCachedStorage,
+		t.RulerStorage,
 		t.Overrides,
 	)
 	if err != nil {
@@ -951,7 +949,7 @@ func (t *Mimir) initRuler() (serv services.Service, err error) {
 	t.API.RegisterRuler(t.Ruler)
 
 	// Expose HTTP configuration and prometheus-compatible Ruler APIs
-	t.API.RegisterRulerAPI(ruler.NewAPI(t.Ruler, t.RulerDirectStorage, util_log.Logger), t.Cfg.Ruler.EnableAPI, t.BuildInfoHandler)
+	t.API.RegisterRulerAPI(ruler.NewAPI(t.Ruler, t.RulerStorage, util_log.Logger), t.Cfg.Ruler.EnableAPI, t.BuildInfoHandler)
 
 	return t.Ruler, nil
 }

pkg/mimir/modules_test.go

@@ -159,11 +159,9 @@ func TestMimir_InitRulerStorage(t *testing.T) {
 			require.NoError(t, err)
 
 			if testData.expectedInit {
-				assert.NotNil(t, mimir.RulerDirectStorage)
-				assert.NotNil(t, mimir.RulerCachedStorage)
+				assert.NotNil(t, mimir.RulerStorage)
 			} else {
-				assert.Nil(t, mimir.RulerDirectStorage)
-				assert.Nil(t, mimir.RulerCachedStorage)
+				assert.Nil(t, mimir.RulerStorage)
 			}
 		})
 	}

pkg/ruler/api.go

@@ -473,7 +473,9 @@ func (a *API) ListRules(w http.ResponseWriter, req *http.Request) {
 	}
 
 	level.Debug(logger).Log("msg", "retrieving rule groups with namespace", "userID", userID, "namespace", namespace)
-	rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, namespace)
+	// Disable any caching when getting list of all rule groups since listing results
+	// are cached and not invalidated and this API is expected to be strongly consistent.
+	rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, namespace, rulestore.WithCacheDisabled())
 	if err != nil {
 		http.Error(w, err.Error(), http.StatusBadRequest)
 		return
@@ -606,7 +608,9 @@ func (a *API) CreateRuleGroup(w http.ResponseWriter, req *http.Request) {
 
 	// Only list rule groups when enforcing a max number of groups for this tenant and namespace.
 	if a.ruler.IsMaxRuleGroupsLimited(userID, namespace) {
-		rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, "")
+		// Disable any caching when getting list of all rule groups since listing results
+		// are cached and not invalidated and we need the most up-to-date number.
+		rgs, err := a.store.ListRuleGroupsForUserAndNamespace(ctx, userID, "", rulestore.WithCacheDisabled())
 		if err != nil {
 			level.Error(logger).Log("msg", "unable to fetch current rule groups for validation", "err", err.Error(), "user", userID)
 			http.Error(w, err.Error(), http.StatusInternalServerError)

pkg/ruler/api_test.go

@@ -163,7 +163,7 @@ func TestRuler_ListRules(t *testing.T) {
 			store.setMissingRuleGroups(tc.missingRules)
 
 			r := prepareRuler(t, cfg, store, withStart())
-			a := NewAPI(r, r.directStore, log.NewNopLogger())
+			a := NewAPI(r, r.store, log.NewNopLogger())
 
 			router := mux.NewRouter()
 			router.Path("/prometheus/config/v1/rules").Methods("GET").HandlerFunc(a.ListRules)
@@ -936,7 +936,7 @@ func TestRuler_PrometheusRules(t *testing.T) {
 				return len(rls.Groups)
 			})
 
-			a := NewAPI(r, r.directStore, log.NewNopLogger())
+			a := NewAPI(r, r.store, log.NewNopLogger())
 
 			req := requestFor(t, http.MethodGet, "https://localhost:8080/prometheus/api/v1/rules"+tc.queryParams, nil, userID)
 			w := httptest.NewRecorder()
@@ -993,7 +993,7 @@ func TestRuler_PrometheusAlerts(t *testing.T) {
 		return len(rls.Groups)
 	})
 
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	req := requestFor(t, http.MethodGet, "https://localhost:8080/prometheus/api/v1/alerts", nil, "user1")
 	w := httptest.NewRecorder()
@@ -1172,7 +1172,7 @@ rules:
 
 			reg := prometheus.NewPedanticRegistry()
 			r := prepareRuler(t, rulerCfg, newMockRuleStore(make(map[string]rulespb.RuleGroupList)), withStart(), withRulerAddrAutomaticMapping(), withPrometheusRegisterer(reg))
-			a := NewAPI(r, r.directStore, log.NewNopLogger())
+			a := NewAPI(r, r.store, log.NewNopLogger())
 
 			router := mux.NewRouter()
 			router.Path("/prometheus/config/v1/rules/{namespace}").Methods("POST").HandlerFunc(a.CreateRuleGroup)
@@ -1207,6 +1207,92 @@ rules:
 	}
 }
 
+func TestAPI_CreateRuleGroupWithCaching(t *testing.T) {
+	// Configure the ruler to only sync the rules based on notifications upon API changes.
+	cfg := defaultRulerConfig(t)
+	cfg.PollInterval = time.Hour
+	cfg.OutboundSyncQueuePollInterval = 100 * time.Millisecond
+	cfg.InboundSyncQueuePollInterval = 100 * time.Millisecond
+
+	const successResponse = `{"status":"success","data":null,"errorType":"","error":""}`
+
+	ruleGroupVersion1 := `name: group1
+interval: 15s
+rules:
+    - record: up_rule
+      expr: up
+    - alert: up_alert
+      expr: up < 1
+`
+	ruleGroupVersion2 := `name: group1
+interval: 15s
+rules:
+    - record: up_rule
+      expr: up
+    - alert: up_alert
+      expr: up <= 1
+`
+
+	mockCache, store := newInMemoryRuleStore(t)
+
+	reg := prometheus.NewPedanticRegistry()
+	// Set rule group limits since this performs a list call to count the current number of rule groups
+	// and we're testing if the API layer is correctly telling the rule store not to serve cached results.
+	r := prepareRuler(t, cfg, store, withStart(), withRulerAddrAutomaticMapping(), withPrometheusRegisterer(reg), withLimits(validation.MockOverrides(func(defaults *validation.Limits, _ map[string]*validation.Limits) {
+		defaults.RulerMaxRuleGroupsPerTenant = 2
+		defaults.RulerMaxRulesPerRuleGroup = 2
+	})))
+	a := NewAPI(r, r.store, log.NewNopLogger())
+
+	router := mux.NewRouter()
+	router.Path("/prometheus/config/v1/rules/{namespace}/{groupName}").Methods(http.MethodGet).HandlerFunc(a.GetRuleGroup)
+	router.Path("/prometheus/config/v1/rules/{namespace}").Methods(http.MethodPost).HandlerFunc(a.CreateRuleGroup)
+
+	// Pre-condition check: the ruler should have run the initial rules sync.
+	verifySyncRulesMetric(t, reg, 1, 0)
+
+	// Store the initial version of the rule group
+	req := requestFor(t, http.MethodPost, "https://localhost:8080/prometheus/config/v1/rules/namespace1", strings.NewReader(ruleGroupVersion1), "user1")
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	assert.Equal(t, http.StatusAccepted, w.Code)
+	assert.Equal(t, successResponse, w.Body.String())
+	// Invalidation of exists and content
+	assert.Equal(t, 2, mockCache.CountDeleteCalls())
+
+	verifySyncRulesMetric(t, reg, 1, 1)
+
+	// Fetch it back and ensure the content is what we expect even though content can be cached
+	req = requestFor(t, http.MethodGet, "https://localhost:8080/prometheus/config/v1/rules/namespace1/group1", nil, "user1")
+	w = httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, ruleGroupVersion1, w.Body.String())
+	// Iter from initial sync, get, iter from sync
+	assert.Equal(t, 3, mockCache.CountFetchCalls())
+
+	// Store a new version of the group that is slightly different
+	req = requestFor(t, http.MethodPost, "https://localhost:8080/prometheus/config/v1/rules/namespace1", strings.NewReader(ruleGroupVersion2), "user1")
+	w = httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	assert.Equal(t, http.StatusAccepted, w.Code)
+	assert.Equal(t, successResponse, w.Body.String())
+	// Invalidating exists and content again
+	assert.Equal(t, 4, mockCache.CountDeleteCalls())
+
+	verifySyncRulesMetric(t, reg, 1, 2)
+
+	// Fetch it back and ensure content is updated to the new version meaning the cache was invalidated
+	req = requestFor(t, http.MethodGet, "https://localhost:8080/prometheus/config/v1/rules/namespace1/group1", nil, "user1")
+	w = httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	assert.Equal(t, http.StatusOK, w.Code)
+	assert.Equal(t, ruleGroupVersion2, w.Body.String())
+	// Iter from initial sync, get, iter from sync, another get, iter from sync
+	assert.Equal(t, 5, mockCache.CountFetchCalls())
+
+}
+
 func TestAPI_DeleteNamespace(t *testing.T) {
 	// Configure the ruler to only sync the rules based on notifications upon API changes.
 	cfg := defaultRulerConfig(t)
@@ -1237,7 +1323,7 @@ func TestAPI_DeleteNamespace(t *testing.T) {
 
 	reg := prometheus.NewPedanticRegistry()
 	r := prepareRuler(t, cfg, newMockRuleStore(mockRulesNamespaces), withStart(), withRulerAddrAutomaticMapping(), withPrometheusRegisterer(reg))
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	router := mux.NewRouter()
 	router.Path("/prometheus/config/v1/rules/{namespace}").Methods(http.MethodDelete).HandlerFunc(a.DeleteNamespace)
@@ -1294,7 +1380,7 @@ func TestAPI_DeleteRuleGroup(t *testing.T) {
 
 	reg := prometheus.NewPedanticRegistry()
 	r := prepareRuler(t, cfg, newMockRuleStore(mockRulesNamespaces), withStart(), withRulerAddrAutomaticMapping(), withPrometheusRegisterer(reg))
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	router := mux.NewRouter()
 	router.Path("/prometheus/config/v1/rules/{namespace}/{groupName}").Methods(http.MethodDelete).HandlerFunc(a.DeleteRuleGroup)
@@ -1336,7 +1422,7 @@ func TestRuler_LimitsPerGroup(t *testing.T) {
 		defaults.RulerMaxRulesPerRuleGroup = 1
 	})))
 
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	tc := []struct {
 		name   string
@@ -1389,7 +1475,7 @@ func TestRuler_RulerGroupLimits(t *testing.T) {
 		defaults.RulerMaxRulesPerRuleGroup = 1
 	})))
 
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	tc := []struct {
 		name   string
@@ -1449,7 +1535,7 @@ func TestRuler_RulerGroupLimitsDisabled(t *testing.T) {
 		defaults.RulerMaxRulesPerRuleGroup = 0
 	})))
 
-	a := NewAPI(r, r.directStore, log.NewNopLogger())
+	a := NewAPI(r, r.store, log.NewNopLogger())
 
 	tc := []struct {
 		name   string
@@ -1551,7 +1637,7 @@ func TestAPIRoutesCorrectlyHandleInvalidOrgID(t *testing.T) {
 
 		r := prepareRuler(t, cfg, newMockRuleStore(map[string]rulespb.RuleGroupList{}), withStart())
 
-		a := NewAPI(r, r.directStore, log.NewNopLogger())
+		a := NewAPI(r, r.store, log.NewNopLogger())
 
 		router := mux.NewRouter()
 		router.Path("/api/v1/rules").Methods(http.MethodGet).HandlerFunc(a.PrometheusRules)